Dissertations / Theses: 'Fields of Research – 290000 Engineering and Technology – 290100 Industrial Biotechnology and Food Sciences'

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Zhang, Jingli 1966. "Evaluation of natural antioxidants." Thesis, University of Auckland, 2004. http://hdl.handle.net/2292/2261.

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This thesis relates the physicochemical properties of phenolic compounds to their antioxidant activities. It focuses on the partitioning of phenolic compounds between hydrophilic and lipophilic environments and the relevance this has to their in vivo health effects. Data in the literature was lacking so the phase partition coefficients (log P) of 53 phenolic antioxidants were measured by reversed-phase HPLC and calculated by log P prediction software. There was a very strong linear correlation between measured and calculated values (r=0.91). The importance of log P in determining antioxidant assay values was then tested by developing an assay system capable of measuring activities of both hydrophilic and lipophilic antioxidants. This Lipid Peroxidation Inhibition Capacity Assay (LPIC), based on using liposomes to simulate a cell membrane environment, was then used to measure the activity of antioxidants with a broad range of structures. The activities were correlated against log p, the difference of heat of formation (∆Hf) and half-wave potential (Ep/2) and used to derive a predictive model to calculate the LPIC activity. There was a highly significant linear correlation between the calculated and measured values. The LPIC activities also correlated well to published LDL inhibition activities but not to measured ORAC activities. These findings suggested that behaviours of antioxidants in the small unilamellar vesicles of the LPIC assay were similar to that in the LDL assay but not to the aqueous phase based ORAC assay. The LPIC assay may therefore be a better indicator of potential health benefits of antioxidants in the human body than the ORAC assay. The possible mechanistic reasons are that it may better reflect ability to prevent the oxidation of LDL blood stream particles that leads to cardiovascular disease and also takes into account the importance of membrane solubility which can raise the cellular concentration and thus potential to protect cells from oxidative damage. KEYWORDS: LPIC, LDL; Antioxidant; Phytochemical; Polyphenolic; Phenolic acid; Flavonoids; log P; Partition Coefficient; Liposome; Lipid bilayer; Lipid Membrane; ORAC; Comet assay; Flow Cytometry.
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Lin, Lu. "Characterizations of oil-in-water (O/W) emulsions containing different types of milk fats prepared using rhamnolipids as emulsifiers : [a thesis presented in partial fulfillment of the requirements for the degree of Master of Technology in Food Technology at Massey University, Auckland, New Zealand] EMBARGOED UNTIL 1 MARCH 2011." Massey University, 2009. http://hdl.handle.net/10179/1323.

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Emulsions containing three different types of milk fat fractions (MF13, MF27 and MF42) and anhydrous milk fat (AMF) were prepared at oil to water (O/W) ratios of 1:9, 3:7, 5:5 and 7:3 using rhamnolipids as emulsifiers. The prepared emulsions were analyzed for their storage stability and properties (colour, particle size, zeta potential and rheology). The effects of various factors (freezing/thawing, heating, pH, salts and ionic strength) on the stability of emulsions were also investigated. All emulsions prepared with an O/W ratio of 7:3, regardless of the type of milk fat, rendered a highly condensed, semi solid and cream-like substance whereas other emulsions containing less oil were in a liquid form. Among the four different O/W ratios tested, the highest emulsion stability during the storage of 12 weeks was observed from the emulsions containing 1:9 O/W ratios, due to a combine effect of smaller emulsion particle size and lower collision frequency between droplets. Interestingly, the emulsions with 7:3 O/W ratios were found to be more stable than the ones with 5:5 O/W ratios. This might be due to the limited movements of closely-packed emulsion droplets induced by the high oil concentration of 7:3 O/W ratios. The emulsion stability was significantly affected by low pH, especially at lower than pH 4, due to the loss of electrostatic repulsions between droplets leading to droplet coalescence and also possibly due to hydrolysis of rhamnolipid molecules. The presence of salts (NaCl, KCl and CaCl2) also rendered the emulsion unstable. The degree of instability was gradually increased with increasing salt concentrations. CaCl2 had the most significant effect even at a very low concentration. The viscosity of emulsions increased with increasing oil concentration but was not affected by the types of milk fats. Emulsions with 3:7, 5:5 and 7:3 O/W ratios exhibited non-Newtonian and shear thinning flow behaviour. At 7:3 O/W ratios, MF13 exhibited gel-like properties whereas both MF42 and AMF emulsions became more solid-like at higher frequency.

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Brennan, Margaret Anne. "Dietary fibres and their properties : the possibility of fibre lowering the glycaemic index of foods post extrusion : presented in partial fulfilment of the requirement for the degree of MPhil in Food Science and Technology at Massey University, Palmerston North campus, New Zealand." Massey University, 2008. http://hdl.handle.net/10179/829.

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A series of experiments were devised in order to establish the relationship between fibre addition to an extruded breakfast cereal base recipe and the physical, chemical and nutritional qualities of the breakfast cereals. A twin screw extruder was used for all experiments. Preliminary investigations using, guar gum and inulin additions, illustrated that screw configuration was important in determining the physical properties (degree of expansion, firmness and crunchiness) of the extruded products. Thus a screw configuration featuring a reverse screw and mixing zone within the barrel was selected for the larger research study. In the extended experimental design guar gum, inulin, wheat bran, swede fibre, and hi-maize were added to a base recipe at; 5, 10 and 15 % of total dry ingredient content. A further experiment was completed to investigate the synergistic effects of adding differing fibres in combination. Results illustrated that soluble dietary fibres (for instance guar and inulin) created a porous, less firm, but crispier breakfast cereals than the insoluble fibres, which generally produced denser, harder products. The inclusion of fibre into the extruded breakfast cereals did not affect the chemical composition of the breakfast cereal significantly (P=0.05) when taking into account the diluting factor of adding the fibre into the base recipe. However moisture loss / retention on extrusion varied significantly (P=0.05) between fibre combinations. Thus the moisture loss of samples containing guar or inulin were greater than those samples containing wheat bran and swede fibre. The process of extrusion did not significantly effect the amount of protein, starch or fibre in the samples when the extruded samples were compared to the control samples. Pasting properties of samples were evaluated using the Rapid Visco Analyser. This was conducted to try to determine associations between starch pasting properties (gelatinisation events) of the raw and extruded samples and the physical or nutritional quality of the products. However, the results did not show clear associations. An in vitro analysis was conducted to determine the effect of fibre addition on starch breakdown and subsequent release of reducing sugars. Breakfast cereals which included wheat bran, guar and swede fibre all showed a reduced rate of starch degradation compared to the control (P=0.05). These fibres appeared to inhibit the rate of enzyme degradation of starch, in effect increasing the amount of slowly digestible starch in the breakfast cereals. Cereal samples containing inulin did not show this pattern. Generally the rate of inhibition was related to the amount of fibre added to the base recipe. When used in combinations, samples containing inulin and hi-maize were not significantly different to the control in terms of reducing sugar release, whereas inclusion of guar gum significantly reduced this release. In conclusion, the addition of selected fibres can be used effectively as a method of manipulating the starch degradation rates of extruded breakfast cereals. This has nutritional implications in terms of glycaemic index and loading of breakfast cereals. Further work is required to develop clearer associations between the events of starch gelatinisation during extrusion and the potential glycaemic response.

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Mais, Anton. "Utilization of sweet potato starch, flour and fibre in bread and biscuits : physico-chemical and nutritional characteristics : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Technology in Food Technology, Massey University." Massey University, 2008. http://hdl.handle.net/10179/921.

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Sweet-potato contains a limited amount of protein, although rich in dietary fibre content and carbohydrate, so a successful combination with wheat flour for bread and biscuit production would be nutritionally advantageous. In particular, the role of these ingredients in relating to acceptability of breads and biscuit with higher percentage of sweet potato starch, flour in wheat flour. In this study, starch, flour and residue fibre of three sweet-potato varieties (red, orange and white -types) were studied. The 5 -10% combination levels for biscuit-making were found to be acceptable, without affecting the quality of the biscuit (combination of texture and biscuit size). In bread, bread containing 15% red and white replacement starches and orange replacement flour was found to be acceptable level, without affecting the quality of the bread, in an attempt to replace wheat at higher per cent level. The physicochemical study was complemented with a nutritional study to determine beneficial effects of food rich in dietary fibre and starches, in the context of improving diet related problems. RVA results showed sweet-potato ingredients affected differently the pasting temperature, peak viscosity and final viscosity of the normal wheat flour (p<0.05). Fibre inclusion showed large reduction in viscosity and swelling of sweet potato starch. Biscuits and breads containing sweet-potato starch and flour are low in amylose, and digest slowly because of lowly oriented and ‘crystalline’ areas within the granules enable to swell or to ungelatinised starch granules, whereas wheat control biscuit was able to gelatinised starch and exerted a greater effect upon digestibility. There are many other factors that need to be considered when analysing the in vitro starch digestibility such including amylose content, amylopectin structure and presence of fibre and gelatinising. Sweet-potato starch, flour and fibre addition show least effect on bread texture and size and starch, flour and fibre replacement. However, in in vitro starch digestibility test higher values RSS was recorded for starch addition followed by flour addition.

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Thamarath, Pranamornkith. "Effects of postharvest treatments on storage quality of lime (Citrus latifolia Tanaka) fruit : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, New Zealand." Massey University, 2009. http://hdl.handle.net/10179/1162.

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Limes (Citrus latifolia Tanaka) are an attractive fruit crop but generally suffer a loss in value as their colour changes from green to yellow. Various approaches were taken to slow degreening including low temperature storage, use of controlled atmosphere (CA) environments, and treatment of fruit with physiologically active agents such as gibberellic acid (GA3). However, the cold storage life of lime fruit can also be restricted by a number of factors including chilling injury (CI) and rots. Various pretreatments such as the use of fungicide (thiabendazole, TBZ) and hot water dipping (HWD) and several postharvest regimes based on temperature conditioning (step down technique) and intermittent warming (IW) regimes were further investigated to protect the fruit against rots and CI during cold storage. The objective of this study was to determine what storage conditions and pretreatments would permit long term storage of NZ limes with minimal loss of quality. CA storage (10% O2 with 0 or 3% CO2) was compared to regular air storage (RA) and IW (varying durations) treatments across a range of temperatures. Although some CA storage regimes could assist in delaying degreening, none of the treatments provided protection against CI. CA storage at 3% CO2 delayed yellowing and gave better fruit quality than the low CO2 treatment. High CO2 CA treatments at 5 or 7°C decreased the rate of colour change compared to other constant temperature treatments but did not protect against CI. CI limited storage of fruit under all conditions at constant low temperatures. Including fungicide (TBZ) in the dip water reduced the incidence of rots and had a secondary effect on protection against CI of lime fruit. However, fungicide use may sometimes exacerbate stresses such as heat injury on lime peel. Hot water dipping has been shown previously to hold potential as a storage pretreatment, but this technique may give risk of damage on produce if it is dipped at too high a temperature. Some HWD treatments did delay degreening, but there was no major effect on CI. HWD at > 47°C for = 4 min caused heat injury to NZ limes. All HWD treatments showed severe CI (>15%) after 10 weeks of cold storage; and HWD fruit stored under RA at 13°C did not show any CI but showed some pitting (= 10%) and degreened rapidly. Overall no suitable HWD treatment for limes was identified in this trial. This project identified the critical periods and temperature conditions for successful IW of limes. The IW conditions successfully delayed losses in quality of lime fruit provided the first warming period was applied within the first 20 days of storage. At least 2-cycle IW was required to maintain lime quality during long term storage. Some benefits were found after just one cycle of IW treatment but there were not enough to extend storage life. IW storage benefited fruit quality and provided the highest overall fruit quality of all postharvest treatments tested. The degreening of lime during cold storage at 5°C could be delayed by IW treatments in which the fruit were stored at 5°C for 12, 16 or 20 days then moved to 15°C for 2 days. Both 2- and 6-cycle IW treatments proved satisfactory for maintaining colour on the green and yellow side of lime for 12 weeks of storage. IW treatments in which fruit were warmed within 20 day of cold storage did not show significant CI symptoms after 12 weeks of storage, and the 2-cycle IW treatment showed only a low percentage of CI fruit at this time. A 2-cycle IW treatment was almost as effective as 6 cycles, and a step down treatment also showed some promising results, indicating that it may be possible to further optimize the time and duration of variable temperature storage regimes to meet both quality requirements and the constraints of temperature management in commercial coolstores. The application of these regimes to other citrus species may also be beneficial. There are a number of physiological explanations that may account for the effectiveness of IW including positive effects on heat shock protein (HSP) and cell membranes. Nutritional factors such as vitamin C and flavonoid compositions were also investigated and fruit that did not show visible CI were found to retain at-harvest levels of these factors. Practical ways of implementing IW are discussed. In order to understand the effectiveness of IW on degreening, I used a logistic model to describe degreening of lime peel. This modelling approach demonstrated that IW did not change the mechanism of lime degreening based on the similarity between the hue values predicted by the model and the actual hue values measured during lime storage. The activation energy (Ea) for degreening based on either hue angle (H°) or colour score (CS) during air storage was estimated to be ~53 and ~86 KJ.mol-1, respectively. Relationship between colour (H° and CS) and chlorophyll content, relationship between reflectance spectra (%), chlorophyll content and H° of lime fruit stored under different conditions are presented and discussed. This data allowed deduction to be made about the changes in individual pigments that are driving colour change during “good” and “bad” storage.

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Jettanapornsumran, Monchanok. "Copigmentation reactions of boysenberry juice : a thesis presented in partial fulfillment of the requirements for the degree of Master of Technology in Food Technology at Massey University, Albany, New Zealand." Massey University, 2009. http://hdl.handle.net/10179/918.

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Colour is one of the main sensory characteristics of berry juice and fruit products and this parameter also powerfully impacts on consumer behaviour. However, the colour of berry juices is unstable and degradation occurs during storage. The main objectives of the project were: to determine the mechanism by which boysenberry juice enhances the colour of other berry juices and to determine if its addition to berry juices will also stabilise the anthocyanin pigments and enhance copigmentation. In this study, total anthocyanin, total phenolic acids, hyperchromic and bathochromic shift and the rate of colour degradation was measured by spectrophotometric techniques. Individual anthocyanin and phenolic acid content were measured in each juice by high performance liquid chromatography (HPLC) were evaluated during storage at 5, 20 and 35?C. Boysenberry juice improved the colour of blackcurrant, cranberry and pomegranate juices immediately after addition; however, only blackcurrant juice colour was stable during storage at 5?C. There was no influence on the stability of total anthocyanins in pomegranate or cranberry juices when boysenberry juice was added. Of the three juices, pomegranate had the highest rate of degradation. The total anthocyanin of blackcurrant enhanced with boysenberry juice was more stable than for cranberry and pomegranate juices. The impact of phenolic acids found in boysenberry juice (kaemferol, quercetin and ellagic acid) on blackcurrant juice colour stability was also investigated. The colour stability of blackcurrant juice was improved by the addition of ellagic acid at 5?C; however, the colour intensity of blackcurrant enhanced with kaemferol and quercetin decreased with storage. The copigmentations between anthocyanins themselves were not found to be a significant effect on colour stability of blackcurrant juice. Ellagic acid had the strongest colour improvement in blackcurrant juice compared to boysenberry juice. In conclusion, ellagic acid as found in boysenberry juice formed intermolecular copigmentation with blackcurrant juice anthocyanins, so this resulted in stabilised juice colour during storage; however, the effect was found when the juice was stored at 5?C only.

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Chollangi, Anusha. "Comparison of two ultrafiltration membrane systems for whole milk feta cheese production : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Food Technology at Massey University, Auckland, New Zealand." Massey University, 2009. http://hdl.handle.net/10179/1060.

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Cheese is one of the most well known food products in the world dating back to the 8th century B.C. There are more than 2000 varieties of cheese that are manufactured all over the world. Feta cheese is a soft white cheese with a salty and slightly acidic taste, which has originated from Greece. Most of the feta cheese manufactured in Greece is consumed locally, the migration of greeks to other parts of the world led to a demand for feta cheese outside of Greece. The spreading of the popularity of feta cheese to other ethnic groups in different parts of the world resulted in the high demand for feta cheese worldwide. The modern and most efficient method of feta cheese production involves a membrane filtration method, known as ultrafiltration. The ultrafiltration process utilises pressure as a driving force to concentrate milk by removal of water and small dissolved molecules. Hollow fibre and spiral wound ultrafiltration membranes are the two types of membranes that are commonly used for cheese production. An extensive amount of research exists on the implementation of ultrafiltration to improve the efficiency of the cheese making process and the performance of the membranes. However, limited research has been conducted on the comparison of the hollow fibre and spiral wound membrane performance in the cheese making process. The objective of the research was to determine if the hollow fibre membranes used at Puhoi Valley Cheese can be replaced with spiral wound membranes without compromising the quality of cheese produced. In order to achieve the objective, feta cheese was produced using hollow fibre and spiral wound ultrafiltration pilot plants. The operating performances of the hollow fibre and spiral wound membrane units were compared. To ensure that the quality of cheese is maintained, the cheese manufactured on the pilot plant units was analysed in terms of composition, microbiology, texture and sensory properties. The cheese made using the hollow fibre membrane pilot plant was compared with the reference sample from Puhoi Valley Cheese as they use hollow fibre membranes to produce feta cheese. The cheese made from the spiral wound membrane unit was also compared to that made by the hollow fibre membrane pilot plant unit. The operating parameters such as the inlet and outlet pressure, pressure difference along the membrane, transmembrane pressure, flow rate, recycle rate (bleed off rate), temperature and the run time were recorded. The operating parameters of the hollow fibre and spiral wound runs were compared with the data from Puhoi Valley Cheese. The quality of cheese made on the hollow fibre and spiral wound pilot plant units were evaluated in terms of composition, texture, microbiology and sensory properties. The composition was defined by the fat, protein, total solids and salt contents. The fat content was determined by utilising the modified Schmid-Bondzynski-Ratzlaff method, protein by the Kjeldahl method, total solids by using the air drying oven and salt percentage by the volhard method. The texture of the cheese was determined by the fracturability and hardness from the compression curve generated using the single bite compression test. The microbiological testing was performed according to New Zealand testing methods for E.Coli, Staphylococcus aureus, coliforms and yeast and mould. The difference from the control method was utilised for sensory evaluation. The acid degree value method was used to determine the lipase activity in feta cheese. It was found from the composition, texture and sensory analysis that the cheese from the hollow fibre pilot plant was different from the cheese manufactured at Puhoi Valley Cheeses (PVC). The spiral wound cheeses were also found to be different to PVC cheese, however the spiral wound cheeses and the pilot plant hollow fibre cheese were the same. The differences between both the pilot plant cheeses and PVC cheese were in terms of the fat, salt, moisture contents and the lipase activity in the cheeses. The fat content in the hollow fibre and spiral wound pilot plant cheeses are lower in comparison to the PVC cheese. This difference in fat content is considered to be due to the difference in the fat to protein ratio of the milk concentrated on the pilot plant and the PVC ultrafiltration system. The lower fat content resulted in firmer cheese than PVC due to more cross linking between the protein strands in cheese. The salt content in the cheeses made using the hollow fibre and spiral wound pilot plants was lower than Puhoi Valley Cheese. This is considered to be due to the low ratio of brine volume to cheese volume used for salting the cheese. The salt content of brine decreases during brining; hence a low ratio of brine volume to cheese volume causes a significant decrease in brine concentration. The decrease in brine concentration decreases the salt intake of the cheese. As salt diffuses in the moisture diffuses out, lower salt content results in higher moisture content in the cheese. As mentioned, the moisture content of the hollow fibre pilot plant cheese was higher than the PVC cheese. The moisture content is inversely proportional to the total solids, hence higher moisture in pilot plant cheeses implies lower total solids than the PVC cheese. The lipase activity results showed that the hollow fibre and spiral wound pilot plant cheeses had higher lipase activity than the Puhoi valley cheese. The differences in lipase activity of the pilot plant cheeses and Puhoi Valley cheese were considered to be due to the incomplete inactivation of lipase present in milk during pasteurisation. The results from texture and sensory evaluation support the above mentioned differences. The microbiology results for all pilot plant cheeses were within the trigger limits set by Puhoi valley cheeses. The results from monitoring the operating parameters of both the pilot plant data show that the permeate flux decreases while the total solids in milk increase with time, which was also observed from the Puhoi Valley Cheese data. However, the rate of decrease of the permeate flux and the increase of the total solids in milk are dependent on the membrane area, feed volume, transmembrane pressure, pressure drop across the membrane and the flow characteristics. The rate of decrease in permeate flux and the rate of increase in the total solids of the hollow fibre runs and spiral wound runs are slightly different. The difference is due to the availability of larger membrane surface area and processing of larger feed volume of milk in the spiral wound runs. The transmembrane pressure and the pressure drop across the membrane were maintained as close as possible to Puhoi Valley Cheese. In conclusion, spiral wound membranes can be used to achieve the desired total solids concentration and successfully make the same feta cheese as the hollow fibre pilot plant. In order to make the same quality of feta cheese as Puhoi Valley Cheese using the spiral wound membrane pilot plant, the same composition of milk used for concentration at Puhoi Valley Cheese needs to be used on the spiral wound pilot plant unit. It is recommended that Puhoi Valley Cheeses should be replaced with spiral wound membranes if they are more economical in terms of cost than the hollow fibre membranes.

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Noisuwan, Angkana. "Effects of milk protein ingredients on physico-chemical properties of rice starch : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University Palmerston North, New Zealand." Massey University, 2009. http://hdl.handle.net/10179/905.

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The overall aim of this thesis is to determine if the interactions between normal and waxy rice starch and milk proteins from four milk protein ingredients, namely skim milk powder (SMP), milk protein concentrate (MPC), sodium caseinate (NaCAS) and whey protein isolate (WPI) do occur, and to identify the mechanisms underlying these interactions. Different milk protein ingredients at various concentrations (0 to 10%, w/w) affected markedly and differently the pasting behaviour of 10% (w/w) rice starches. SMP delayed the pasting of both rice starches by increasing the onset temperature (Tonset) and the peak viscosity temperature (Tpeak) of pasting. This was mainly due to the presence of lactose and ions, which was further supported by the investigation of the effects of UFSMP (a solution of salts and lactose present in SMP at their proper concentration) and lactose. The addition of NaCAS also delayed the pasting of rice starch; Tpeak in the case of both starches was increased. For normal rice starch paste, MPC and WPI decreased the Tpeak. MPC had no affect on Tpeak of waxy rice starch paste. The qualitative viscoelastic behaviour of rice starch/milk protein ingredient gels obtained from the above pastes was dominated by the continuous phase made of the starch molecules. There was evidence, as indicated by confocal microscopy, of phase separation between the milk proteins of SMP and MPC and the two starches. The phase separation was not observed in the addition of either NaCAS or WPI. Studies on the thermal behaviour of rice starch/milk protein ingredient mixtures by differential scanning calorimetry (DSC) showed that SMP, similarly to UFSMP, delayed the gelatinization of both starches. NaCAS also delayed the gelatinisation of both starches but had a greater effect on waxy than normal rice starch. The addition of NaCAS did not affect Tonset but increased Tpeak for normal rice starch, whereas the gelatinisation temperature of waxy rice starch was highly affected by the addition of NaCAS with both Tonset and Tpeak shifted to higher temperatures. MPC had no affect on the gelatinization temperature of normal rice starch, whereas the gelatinization temperature of waxy rice starch was increased by the addition of MPC. The addition of WPI to both rice starches showed two thermal transitions. The first of these was due to the gelatinisation of the starches and the second to the denaturation of ß-lactoglobulin (ß-lg). The addition of WPI to normal rice starch showed that the thermal behaviour of normal starch and protein were independent from each other. In contrast, the thermal behaviour of waxy rice starch was modified by the addition of WPI; both Tonset and Tpeak were increased. SMP decreased the Tonset of swelling, swelling ratio and the amount of starch leaching from both starches. These observed changes were due to the presence of lactose and ions in SMP. NaCAS slightly increased Tonset of swelling but the amount of starch leaching was reduced for both rice starches. The rigidity of both starches tended to increase in the presence of NaCAS. MPC and WPI affected the swelling behaviour of normal and waxy rice starch differently. A dramatic increase in the swelling of normal rice starch/MPC or WPI mixtures was observed, whereas this trend was not evident for waxy rice starch/ MPC or WPI mixtures. The difference in the water holding ability and gelatinization peak temperatures of the two starches over the temperature range at which whey proteins denature and form gels are believed to be responsible for the observed differences. The results from confocal microscopy showed that milk proteins, such as a-casein, ß- casein, ß-lg and a-lactalbumin (a-la), were adsorbed onto the granule surface of both normal and waxy rice starch. The mechanism for this adsorption is the hydrophilic interactions; hydrogen bonds between hydroxyl group from terminated glucan molecule that protrude around starch granule surface-hydroxyl; amino, or other electron-donation or electron-accepting groups of the added proteins. Using sodium dodecyl sulfatepolyacrylamide gel electrophoresis (SDS-PAGE) it was found that for SMP and MPC the adsorbed as- to ß-casein ratio on both starches was similar to the as-casein to ß- casein ratio in the casein micelle at low SMP and MPC concentrations. But at high concentrations of SMP or MPC, this ratio decreased indicating that more ß-casein was adsorbed preferentially to as-casein. In the case of NaCAS, as-casein was adsorbed preferentially to ß-casein. Moreover, there was evidence of multilayer adsorption of ascasein into the surface of rice starch granules. Compared to the other milk protein ingredients, very small amounts of the ß-lg and a-la from WPI were adsorbed onto starch granules. However, the adsorbed amounts of ß-lg and a-la from WPI continuously increased with increasing WPI concentration, suggesting that these two proteins, particularly ß-lg, adsorbed in multilayers too.

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Bennett, Hayden Albert Edward. "Aspects of fouling in dairy processing : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Engineering at Massey University, Palmerston North, New Zealand." Massey University, 2007. http://hdl.handle.net/10179/981.

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Fouling of heat treatment equipment in the dairy processing industry is an expensive and persistent problem. The objective of this work was to develop a better understanding of the mechanisms of dairy fouling in heat exchangers and identify methods to control this build-up. This was part of a larger project investigating the interaction between spore-forming thermophilic bacilli (thermophiles) contamination and fouling deposits on internal surfaces of equipment. Two systems were developed to monitor the onset and build-up of fouling on the internal surfaces of two research heat exchangers. The first used a commercial sensor to measure the local heat flux and the temperature on the hot side of a plate type heat exchanger. The heat transfer coefficient was calculated and normalised with its value at the start of the run to reflect the contribution of fouling deposits to the thermal resistance, thus giving a real-time estimate of the rate of fouling. The second system used an energy balance over a tubular type heat exchanger and measured inlet and outlet temperatures to estimate the overall heat transfer coefficient thus giving a global measurement of fouling over the tubular heat exchanger. In both systems the plot of normalised heat transfer coefficient over time often stayed constant over an induction period, which was followed by a falling period indicative of growth in the fouling layer thickness and/or mass. Each system was validated by comparing the final value of the normalised heat transfer coefficient with direct measurements of fouling made at the end of a run namely: fouling deposit height for the local measurement and fouling deposit mass for the global measurement. The normalised heat transfer coefficient reported by each system correlated well with the corresponding direct measurement of the fouling layer. An important factor identified in this study was the effect of air bubble nucleation on fouling deposits. It was shown that bubbles that formed on the heated surface greatly reduced the length of the induction period to a matter of seconds rather than hours, as found in previous studies of fouling in the absence of surface bubbles. The rate of fouling was also enhanced while the bubbles remained at the surface. The structure of bubble type fouling layers was linked to the behaviour of the bubbles at the heated surface. Visual observations of these bubbles showed evidence of growth, vibration and coalescence during their period of attachment to the heated surface. Deposits from bubble type fouling consisted of all solid components found in the original milk solution, except lactose, in approximately the same ratio. By contrast fouling deposits reported in the literature with systems operating under the traditional protein denaturation mechanism were reported to consist mainly of whey proteins. Bubble induced fouling can be limited in a number of ways, the most effective being to maintain a high operating pressure in the equipment to ensure nucleation does not occur. Experiments conducted in this study showed that a pressure of 130 kPa.g was sufficient to suppress all bubble nucleation at the heated surface at a temperature of 90°C. Another method identified was the use of high linear fluid velocities to entrain any surface bubbles into the processing stream immediately upon nucleation. Linear velocities above 1.0 m/s were shown to achieve this goal in the miniature plate heat exchanger tested. However, this method is only partially successful because the local linear velocity varies with position in heat exchange equipment of complex geometries and can drop below the mainstream average velocity causing surface bubbles to form, especially in recirculation regions behind flow obstacles. A more reliable method, in situations where high operating pressures could not be used, involved conditioning the heated surface with a thin protein layer during the first few minutes of a run. Conditioning the surface resulted in bubble suppression even at high temperatures and low pressures, thus greatly extending the length of the induction period. Trials performed in this study showed that the addition of a proteolytic enzyme produced by psychrotrophic microbes greatly increased fouling. The enzyme destabilised the caseins which could attach directly to the heat exchange surface independently from the bubble fouling mechanism. Thus the quality of the milk is another important factor to consider. However, the addition of enzymes produced by thermophilic bacilli isolated from milk powder plants did not increase fouling. A theory describing the air bubble induced fouling mechanism is presented along with recommendations on how to reduce this fouling contamination in processing equipment.

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Oommen, Retty. "Production of blue pigments from the callus cultures of Lavandula augustifolia and red pigments (betalain) from the hairy root culture of Beta vulgaris : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Biotechnology at Massey University, Palmerston North, New Zealand." Massey University, 2009. http://hdl.handle.net/10179/997.

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Plants are used to produce many secondary metabolites that are too difficult, expensive or impossible to make by chemical synthesis. Conventional cultivation of plants is of course subject to vagaries of weather, pests and availability of land; hence, the interest in highly controlled culture of plant cells and hairy roots in bioreactors as methods of producing various products. This project focussed on production of blue and red colors of Lavandula augustifolia and Beta vulgaris, respectively. Callus and suspension cell culture were successfully produced from L. augustifolia after extensive trials, but hairy roots could not be generated from this species. In contrast, a successful protocol was developed for consistently producing hairy roots from B. vulgaris, but calli could not be generated from this species. Effects of medium composition on growth of L. augustifolia calli and freely suspended cells and production of the blue pigment by the latter, were investigated. Optimal production of callus occurred in full-strength Murashige and Skoog (MS) medium supplemented with 2 mg/l of indole-3-acetic acid (IAA) and 1 mg/l of kinetin. Stable suspension cultures could be produced and maintained in full-strength MS medium supplemented with 1 mg/l each of IAA and kinetin. In suspension culture in full-strength MS medium, the following hormone combinations were tested: (1) 1 mg/l each of indole-3-acetic acid (IAA) and kinetin; (2) 2 mg/l of IAA and 1 mg/l of kinetin; (3) 2 mg/l of IAA and 1 mg/l of benzyl amino purine (BAP); and (4) 2 mg/l each of IAA and BAP. Combination (3) maximized cell growth, but the highest cell-specific production of the blue pigment was seen in combination (2), although pigment production occurred at all hormone combinations. The medium formulation that gave the best production of the pigment in shake flasks was scaled up to a 2 L aerated stirred tank bioreactor, but both the biomass and pigment productivities were reduced in the bioreactor apparently due to the high shear stress generated by the Rushton turbine impeller. Compared to suspension cultures of L. augustifolia, the hairy root cultures of B. vulgaris grew extremely rapidly. Hairy roots also produced large amounts of the red pigments. Growth of hairy roots was influenced by the composition of the medium. Although the full strength MS medium better promoted biomass growth compared to the half-strength MS medium, the final concentration of the biomass and the pigment were nearly the same in both media. Attempts were made to enhance production by using various hormones (i.e. naphthalene acetic acid, BAP, IAA added individually at a concentration of 0.5 mg/l), but none of the hormones proved useful. BAP adversely affected the growth of hairy roots. In summary, production of pigments by suspension culture of L. augustifolia and hairy root culture of B. vulgaris, is technically possible, but requires substantial further optimization for enhancing productivity than has been possible in this project. iii

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Md, Zain Siti Norbaizura Binti. "Biofilm formation of Enterobacter sakazakii on three different materials of infant feeding tube : a thesis presented in partial fulfillment of the requirements for the degree of Master of Technology in Food Microbiology at Massey University, Palmerston North, New Zealand." Massey University, 2009. http://hdl.handle.net/10179/1012.

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The aim of this study was to observe biofilm formation by Enterobacter sakazakii (E. Sakazakii) from different clinical, dairy and environmental origins on three infant feeding tubes made of different materials. Infant formula milk was selected as the medium for E. sakazakii growth. Seventeen isolates from different origins were retrieved and tested for purity, using a plating method and biochemical tests to eliminate the non E. sakazakii strains from this study. A method to rapidly and accurately detect viable cells of E. sakazakii on infant feeding tube surfaces using of the BacTrac® 4000 microbiological growth analyser was developed. The sources of errors such as from cleaning, operation and handling procedures were assessed prior to experimental runs. The strength of biofilm formation by different isolates of E. sakazakii on plastic surfaces was scrutinised using a microtiter plate assay. The results from the microtitre plate assay were based on the absorbance at 550 nm of crystal violet stained films and showed that all the clinical isolates were able to attach and form strong biofilms on the plate. Some environmental isolates formed strong or weak biofilms and some did not produce biofilm at all. However, dairy isolates formed both strong and weak biofilms in the microtitre plate when incubated in 10% reconstituted infant formula milk. The further studies were to quantify biofilm formation by three isolates of different origin on three different materials of infant feeding tubes using a batch system. Tubing pieces were incubated with infant formula milk inoculated with E. sakazakii cells at approximately 8 log CFU mL-1 and the biofilm formation was assessed at three time intervals: 4, 12 and 24 hours. Biofilm formation on the tubing by clinical isolates was also observed using epifluorescence microscopy and the scanning electron microscope. E. sakazakii from clinical, dairy and environmental isolates were able to form biofilm on three different materials of infant feeding tubes. The results showed that the initial attachment at 4 h on silicone tubing was low compared with the other two tubes. The scanning electron micrographs showed the surface characteristics of each tubing and the biofilm formation by E. sakazakii clinical isolates after 4, 12 and 24 hours. Silicone tubing appeared to be the best choice for premature babies that need feeding using feeding tubes, as it was slow to become colonised compared with the PVC and polyurethane tubing.

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Ries, Daniel. "Studies on the antioxidant activity of milk proteins in model oil-in-water emulsions : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology, Riddet Institute, Massey University, Palmerston North, New Zealand." Massey University, 2009. http://hdl.handle.net/10179/1084.

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The present study was aimed at extending our knowledge of the antioxidative properties of the milk protein products, whey protein isolate (WPI) and sodium caseinate (NaCas), in oil-in-water (O/W) emulsions rich in polyunsaturated fatty acids (PUFAs). In particular, the objective was to contribute to our understanding of the compositional and processing factors that influence the oxidative stability of protein-stabilised O/W emulsions. Linoleic acid (approximately 60 %) was used as the lipid for the oil phase (10.6 %). The emulsion samples were usually incubated at 50 °C to accelerate lipid oxidation. Lipid oxidation indicators were lipid hydroperoxides and headspace hexanal, determined by solid phase microextraction (SPME) combined with gas chromatography (GC). WPI- or NaCas-stabilised emulsions were prepared using a wide range of protein concentrations (0.5, 1.0, 2.0, 3.0, 4.0, 7.0 or 10.0 %) at two droplet sizes (d32 = 0.31 and 0.65 µm). In general, higher lipid oxidation levels were found for the larger droplet size. Increasing protein concentration led to a decrease in the lipid oxidation rate. The greatest decrease in lipid hydroperoxide levels (values after 4 h) occurred at up to 4.0 % protein concentration. The greatest decrease in hexanal levels (values after 24 h) occurred at up to 4.0 % protein concentration in WPI emulsions (0.31 µm). The hexanal levels were more independent of the protein concentration in the other emulsion types. The hexanal level decreased at protein concentrations > 4.0 % in NaCas emulsions (0.31 and 0.65 µm) and at protein concentrations > 7.0 % in WPI emulsions (0.65 µm). The difference between lipid hydroperoxide generation in emulsions with small and large droplet sizes decreased with increasing protein concentration. This effect was more pronounced in NaCas emulsions. In general, NaCas was a better inhibitor of lipid oxidation than WPI, but WPI appeared to be the better antioxidant at some droplet size/protein concentration combinations. The protein in the continuous phase, i.e. the unadsorbed protein, played an important role in lipid oxidation. In principal, the lipid hydroperoxide and hexanal levels showed the same development over the continuous phase protein concentration as over the protein concentration in WPI and NaCas emulsions (d32 = 0.31 µm). A low NaCas level in the continuous phase already led to a relatively low hexanal level, whereas a higher WPI level was required. When NaCas solution was added to a WPI emulsion or WPI solution was added to a NaCas emulsion, a synergistic antioxidative effect was observed. The high molecular weight fractions (molecular weight = 12000-14000) of WPI and NaCas contained pro-oxidative metal ions that contributed to lipid oxidation in the emulsions. An enrichment of NaCas emulsions with the low molecular weight fraction of NaCas (with a molecular weight = 12000-14000) notably inhibited lipid oxidation. An enrichment of WPI emulsions with the low molecular weight fraction of WPI (with a molecular weight = 12000-14000) also seemed to inhibit lipid oxidation, but the effect was not significant. The protein solutions were enriched with these fractions before emulsion preparation. Pure WPI solution or mixed WPI/NaCas (1:1, weight/weight) solution with 1.12 or 2.24 % protein concentration was heated at 84 °C for up to 40 min, cooled and then used to prepare emulsions. Lipid oxidation was generally not affected by the heat treatment or the degree of whey protein denaturation. However, at the lower WPI concentration, more hexanal was produced for the longer heating times (20, 30 and 40 min) and this appeared to be connected with the physical instability of the emulsions. Greater oxidative stability was found at the higher protein concentration and when the proteins were mixed, pointing to a possible synergistic antioxidative effect of WPI and NaCas. The addition of the free radical source 2,2’-azobis(2-amidinopropane) dihydrochloride (AAPH) greatly increased the oxygen uptake and the generation of lipid hydroperoxides in the emulsions. The oxidative stability increased with increasing protein concentration (1.0, 4.0 and 7.0 %). NaCas had a greater antioxidative effect than WPI. The inhibition of oxygen uptake appeared to be largely influenced by the free-radical-scavenging activity of the system, determined by the protein type and the protein concentration, as the radicals were produced linearly over time and oxygen was consumed linearly over time. It can therefore be concluded that free-radical-scavenging activity represents a major antioxidative mechanism of the milk proteins. Oxygen was consumed much faster in emulsions than in protein solutions when the same level of AAPH was incorporated. In a WPI (1.0 % protein) emulsion, much lower levels of protein hydroperoxides than of lipid hydroperoxides developed. This pointed to a much greater reactivity of linoleic acid than of the milk proteins with oxygen. In contrast, the exposure of WPI to oxidising linoleic acid in an emulsion (1.0 % protein) or to AAPH in aqueous solution led to oxidative damage of the whey proteins, indicated by the loss of amino acids. The loss of specific amino acids was different for proteins in the continuous phase or cream phase of an emulsion or in WPI solution. The present study confirms the antioxidative potential of WPI and NaCas and gives new insights into their functionality as oxidative stabilisers in O/W emulsions.

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Oh, Hyunah Eustina. "High-pressure-induced starch gelatinisation and its application in a dairy system : a thesis presented in partial fulfilment of the requirements for the Doctor of Philosophy in Food Science at Massey University, Auckland, New Zealand." Massey University, 2009. http://hdl.handle.net/10179/1075.

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This study investigated pressure-induced starch gelatinisation in water and milk suspensions. A rheological method, termed ‘pasting curves’, provided an objective and analytical means to determine the degree of pressure-induced starch gelatinisation. In addition, a polarised light microscope was used to observe birefringence of the starch granules and the degree of starch swelling was measured. The preliminary investigation into pressure-induced gelatinisation of six different starches showed that potato starch was the most pressure resistant and was not gelatinised after a pressure treatment of 600 MPa for 30 min at 20 °C. Waxy rice, waxy corn and tapioca starches showed complete gelatinisation after the same treatment while normal rice and normal corn starches were only partially gelatinised despite the disappearance of birefringence. Based on the preliminary study, two starches (normal and waxy rice starches) were selected for more detailed studies. The effects of treatment conditions (pressure, temperature and duration) on the gelatinisation were investigated with these selected starches. The degree of gelatinisation was dependent on the type of starch and the treatment conditions. The results also indicated that different combinations of the treatment conditions (e.g. high treatment pressure for a short time and low treatment pressure for a longer time) could result in the same degree of gelatinisation. Both starch types exhibited sigmoidal-shaped pressure-induced gelatinisation curves and there was a linear correlation between the degree of swelling and the apparent viscosity of the starch suspension. After treatments at =500 MPa for 30 min at 20 °C, both starches lost all birefringence although the apparent viscosity and the degree of swelling of normal rice starch did not increase to the same extent as observed in waxy rice starch. Pressure-induced gelatinisation of starch was retarded when starch was suspended in skim milk. This was attributed to the effect of soluble milk minerals and lactose present in the milk whereas milk proteins (casein and whey) did not affect the degree of gelatinisation at the levels present in 10% total solids skim milk. The presence of soluble milk and/or lactose may lead to less effective plasticising of starch chains by the suspension medium. Interactions between milk components and starch molecules may also play a role in retarding gelatinisation by reducing the mobility of starch chains. The functionality of starch in a dairy application was tested using acid milk gels as a model system. Skim milk with added starch (waxy rice or potato starch) was either pressure treated (500 MPa, 20°C, 30 min) or heat treated (80°C, 30 min) and subsequently acidified to form acid milk gels. The addition of waxy rice starch resulted in firmer acid milk gels, and increasing the amount of starch caused an increase in the firmness of both pressure-treated and heat-treated samples. However, pressure-treated samples with added potato starch did not show significant changes in the firmness whereas the heat-treated counterparts showed a marked increase in the firmness as the level of potato starch increased. The difference between the effects of the two different starches can be explained by the extent of starch gelatinisation in skim milk. Starch granules absorb water during gelatinisation whether induced by pressure or heat which effectively increases milk protein concentration in the aqueous phase to form a denser protein gel network on acidification. The firmness of acid milk gels can be increased by adjusting the pH at pressure or heat treatment to higher than the natural pH of milk. The effect of pH at pressure or heat treatment and addition of starch on the acid milk gel firmness was additive and independent of each other up to a starch addition level of 1%. This study provided an insight into pressure-induced gelatinisation of starch by showing gelatinisation properties of starches of different botanical origins and the effects of the treatment conditions (treatment pressure, treatment temperature and duration) on the degree of gelatinisation. Furthermore, the results from the pressure treatments of starch in dairy-based suspensions showed that pressure-induced gelatinisation was affected by other components in the system. These results demonstrate the importance of understanding the gelatinisation properties of starch in complicated food systems in which a number of other components are present. In terms of the application of starch in dairy systems, when starch was added to milk and gelatinised by pressure treatment, the acid milk gel produced by subsequent acidification was firmer than the acid milk gel made from skim milk alone.

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Srichantra, Arunee. "Studies of UHT-plant fouling by fresh, recombined and reconstituted whole milk : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Engineering." Massey University, 2008. http://hdl.handle.net/10179/961.

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The objective of this study was to investigate the effects of preheat treatments on fouling by fresh whole milk (FWM), recombined whole milk (RCB) and reconstituted whole milk (Recon) in the high-temperature heater of indirect UHT plants. Various preheat treatments prior to evaporation during milk powder manufacture were applied to skim milk powder (SMP, 75 °C 2 s, 85 °C, 155 s and 95 °C, 155 s) and whole milk powder (WMP, 95 °C, 33 s). These preheat treatments were so-called “evaporator preheat treatments”. Skim milk powder (SMP) and whole milk powder (WMP) were derived from the same original batch of pasteurised FWM to remove the effects of the variation in milk composition between different milk batches. These SMPs were recombined with anhydrous milk fat and water to prepare RCB, and WMPs were reconstituted with water to prepare Recon. Then, (homogenized) FWM, RCB and Recon were subjected to various preheat treatments (75 °C, 11 s, 85 °C, 147 s and 95 °C, 147 s) prior to UHT processing. These preheat treatments were so-called “UHT preheat treatments”. Temperature difference (hot water inlet temperature – milk outlet temperature) was taken as a measure of the extent of fouling in the high-temperature heater. The slope of the linear regression of temperature difference versus time (for two hours of UHT processing) was taken as fouling rate (°C/h). Increasing both evaporator and UHT preheat treatments resulted in increasing fouling rate and total deposit weight for all three whole milk types for several milk batches. In the case of FWM, there was no reduction in fouling rate with increasing UHT preheat treatment whether FWM was homogenized then preheated, preheated then homogenized or not homogenized at all. These findings, which are wholly consistent and well replicated, are in apparent conflict with the results of most previous comparable studies. Possible reasons for this are explained. Further investigations of the effects of homogenization relating to the role of whey protein on the surface of the fat globules showed that whey protein associated with the membrane covering the surface of fat globules for homogenized then preheated FWM, RCB and Recon and that association increased with increasing heating process stage. The increasing association of whey protein with the milk fat globules membrane with increasing severity of heating process stage became faster when preheat treatment was more severe: the association of whey protein plateaued on intermediate temperature heating when the milks were preheated at 75°C, 11 s and on preheating when the milks were preheated at 95°C, 147 s. In the case of FWM, the thickness of the membrane covering the surface of fat globules for homogenized then preheated FWM, which increased with the severity of heating process stage, was greater than the thickness of the membrane in preheated then homogenized FWM. Preheating then homogenization resulted in the greater interfacial spreading of small molecules on the surface of fat globules, i.e. whey protein or small molecules from the disintegration of casein micelles during preheating. Possible basic mechanisms for UHT fouling in the high-temperature heater include: the reduction in the solubility of calcium phosphate and the deposition of protein as fat-bound protein and non-fat-bound protein. When non-fat-bound protein in milk plasma deposited, it could be a carrier for the deposition of mineral, such as, the precipitate of calcium phosphate in the casein micelles or the deposition of complexes between whey protein and casein micelles.

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Jansen, Eion. "Nutritional characteristics of New Zealand export lamb and functional properties of selected beef forequarter muscles : a thesis presented in partial fulfilment of the requirements for the degree of Masters of technology in Bioprocess Engineering at Massey University, Palmerston North, New Zealand." Massey University, 2001. http://hdl.handle.net/10179/895.

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Richmond Ltd. has recently undergone a change in strategy, away from the traditional commodity based meat industry, towards the modern food business. To do this, opportunities to add value to their current product range must be identified. This involves the conversion of traditionally low value commodity based products into products that demand a premium. An example of this is converting muscles that are currently used for grinding meat into a further processed convenience food (i.e. ready meals). Another method is to add further value to premium products by making them more appealing to consumers (i.e. nutritional information on labels). This work details investigations into the functional properties of selected beef forequarter muscles (low value commodity products) and the nutritional properties of selected export lamb products (premium products). The functional properties of a number of beef forequarter muscles were measured to identify which had the best potential for further processing applications with respect to ready meals. The functional properties of tenderness, cook loss and shrinkage were measured for the Latissimus Dorsi, Pectorialis Profundus (Point End Brisket), Infraspinatus (Cross Cut Blade), Triceps Brachi Longhead (Main muscle in Bolar Shoulder Clod), Supraspinatus (Chuck Tender), Serratus Ventralis and Triceps Brachi Medialhead (Muscle in Bolar Shoulder Clod. From the tests conducted the Infraspinatus and the Triceps Brachi Longhead have been identified as having the best functional properties with respect to further processing for ready meal applications. As well as conducting tests to identify the forequarter muscles with the best potential for further processing applications, investigations were carried out to identify cooking regimes that would optimise the functional properties. This work confirmed that there are three major chemical reactions, which determine the resultant functional properties of cooked meat. They are the denaturation and aggregation of the myofibrillar proteins and the denaturation and solubilisation of connective tissue (collagen). At around 50°C myosin (45% to 50% of the myofibrillar proteins) denatures, which results in a substantial increase in cook loss and reduction in water holding capacity. At around 60°C collagen (main connective tissue protein) denatures, which results in a substantial increase in tenderness and increase in cook loss. This is because as the collagen denatures it loses it mechanical strength (increase in tenderness) and can no longer support its own structure, and causes it to contract. This contraction causes fluid within the meat and cook loss caused by the denaturation of myosin to be expelled from the meat by compressive forces (squeezed out). At around 70°C actomyosin (22% of the myofibrillar proteins) denatures. This results in a substantial increase in the cook loss and firming of the meat. The increase in cook loss or decrease in water holding capacity that occurs with myofibrillar protein denaturation is due to the fact that when these proteins denature and aggregate their ability to bind water is greatly reduced. From the results of the cooking regime trials it is recommended that for functional property considerations that during the cooking of further processed meat products (i.e. ready meal applications) a meat temperature of 62°C should be aimed for, for the slowest heating region during cooking (usually the centre). This is because it has been identified that a cooking temperature of 65°C should not be exceeded otherwise detrimental effects can occur to the functional properties of the cooked meat. For health concerns a 7D bacterial death reduction has to be achieved. This means that for a cooking temperature of 62°C the meat has to be held at this temperature for at least 5 minutes. Therefore the total cooking time would be the time needed to heat all the meat to 62°C plus 5 minutes to ensure a safe product. The heating or cooking system employed should also ensure that a minimal amount of the meat is heated above 65°C. This can be easily achieved by minimising the external cooking temperature, but long cooking times will result. An industrial cooking process will be a compromise between the cost associated with longer residence time and product functionality. As mentioned earlier another way to add value is to supply nutritional information for selected cuts. Consequentially one of the objectives of this project was to provide some nutritional information for selected meat cuts. Though the primary objective of this part of the project was to develop a method for producing the needed information, so that Richmond N.Z. Ltd. can develop further information on an as needs basis. The nutritional characteristics of a number of export lamb cuts from the saddle region has also been investigated and a method devised to allow further characterisation of other cuts. The method involves breaking down a standard cut into its constituent components (e.g. Frenched rack consists of loin eye, fat cap, intercostals and fatty tissue). The constituent components are tested for their nutritional properties. The frenched rack nutritional properties are calculated from the nutritional properties of the constituents components and the yield data (percentage of each constituent component within a frenched rack) for frenched racks. This method allowed the identification of the main sources of variation for nutritional characteristics. These differences were found to be caused by the lean to fat ratio, not nutritional differences in lean tissue from the same region of lamb (i.e. loin eye and tenderloin very similar nutritionally). The difference in lean to fat ration also accounts for the variation between grades (i.e. PX grade lamb cuts have a higher fat content than YX grade lamb cuts due to PX grade cuts having a higher percentage fat tissue in their cuts). The cuts characterised were the shortloin section (whole section or chop), rack section (whole section or chop), 75mm racks frenched 25mm, boneless loin and tenderloin for both PX and YX grade lamb. The method will be applicable to other regions of lamb (i.e. hindquarter and forequarter) for which nutritional information already exists, but for which yielding data will have to be collected. The method would also be applicable to other species such as beef and venison, but both nutritional data for constituent components and yielding data would have to be collected.

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Han, Jin. "The effect of pre-rigor infusion of lamb with kiwifruit juice on meat quality." Diss., Lincoln University, 2008. http://hdl.handle.net/10182/334.

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Tenderness, juiciness, colour and flavour are the most important meat quality attributes affecting the consumer acceptance. Maintaining the consistency of meat products by avoiding variable quality has become a major concern and great challenge to the meat industry. This in turn will also benefit meat end-users in the marketplace by having more tender meat. The present study was designed to evaluate the overall effects of pre-rigor infusion with kiwifruit juice, which contains the plant protease, actinidin, on lamb quality. A total of 18 lambs (12 months old) were divided into three treatment groups (6 lambs per each treatment). After exsanguination, lamb carcasses were infused (10% body weight) with fresh kiwifruit juice (Ac), water (W) and compared with a noninfusion treatment which acted as a control (C). Samples from different muscle/cuts (longissimus dorsi (LD) vs leg chops) at different post-mortem times (1 day post-mortem vs. 3 wks vacuum packaged storage at 2°C) and display time (0 to 6 days after the post-mortem storage) were analysed to monitor the changes on meat physical properties (e.g., tenderness, temperature, drip and cooking loss, colour), biochemical changes (pH, proteins and lipids) and volatile flavour compounds after the infusion treatments. The most tender meat (lowest shear force values) (P < 0.001) detected in the Ac carcasses post-mortem compared with C and W carcasses demonstrated that kiwifruit juice was a very powerful meat tenderizer, and could contribute to the meat tenderization process efficiently and effectively. Compared with C and W carcasses, the enhanced proteolytic activity (P = 0.002) resulting from the actinidin in kiwifruit juice in Ac carcasses caused degradation of the myofibrillar proteins and the appearance of new peptides during postmortem ageing. A slight positive effect in a*-value (redness) and decreased lipid oxidation, found in leg chops, was thought to be caused by the natural antioxidants in kiwifruit juice. Kiwifruit juice infused into the meat did not alter (P > 0.05) the volatile flavour compound profile indicating that the meat from Ac treated carcasses maintained its natural lamb flavour. No treatment differences were found for the temperature decline (P > 0.05) between the infused treatments and C. The higher rate of pH decline (P < 0.05) found in W carcasses might have contributed to the higher drip and cooking loss. The unbound water in meat might contribute to the higher L*-values (lightness) found in W carcasses. In summary, the proteolytic tenderizing infusion treatment using kiwifruit juice is a feasible approach for the commercial meat industry to increase profits, and also could satisfy the eating quality standards required by the consumers. In addition, tenderizing meat by using kiwifruit juice could also provide the kiwifruit processors an additional option for use of their product to gain a more profitable return.

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Tran, Mai Thu Thi. "Frying of potato crisps - an investigation aiming at reduction oil content and acrylamide formation." 2006. http://hdl.handle.net/2292/2318.

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Reducing oil content, minimizing any carcinogenic acrylamide in the high temperature frying process for potato crisps, and producing good products with considerable crispiness and acceptable color were the objectives of this research. Vacuum frying with pre-treatment of potato crisps was investigated as an effective process for oil content reduction. Pre-drying and subsequent dipping (PSSD) in a sugar solution (‘sugar dipping’) were considered as an advantageous procedure for the treatment of potato crisps before frying in order to reduce oil uptake during frying. Vacuum frying was observed as an excellent process to decrease significantly the acrylamide formation at low temperature frying of potato crisps. In this study, potato crisps were respectively blanched, pre-dried, and dipped in a solution of sugar (23.07 wt %) for two seconds, before vacuum frying at 120oC, 110oC under different vacuum pressures (170mbars, 150mbars, 100mbars and 50mbars in separate experiments). Conventional frying at 180oC was also used as the control to benchmark the reductions in the oil contents and acrylamide formation among various techniques. There was a significant reduction in oil content of the potato crisps observed when the new techniques were applied. The crisps that had been pre-treated and fried with conventional frying have given the result of 30 wt % reduction. The crisps that were fried under vacuum frying achieved greater oil reduction with varying percentages when applying different pretreatments. The lowest oil content was achieved when the potato crisps were fried at 110oC and 150 mbars giving 58 % reduction on the dry basis compared with control samples. There are various advantages of the technique with PSSD as we have discovered: it is simple and can be applied in potato crisp industries in continuous mode in both vacuum and conventional frying systems. The crisps that had been treated with pre-drying and subsequent sugar solution dipping and then fried were crunchier and possibly had better perceived taste to the consumer, due to the small sugar addition. Pre-drying and vacuum frying have all turned out to be excellent techniques to reduce acrylamide formation in potato crisps as we have found in this study. Vacuum frying at 120oC and 150 mbars reduced acrylamide formation by 80 to 85%. The 95% reduction was obtained when the crisps had been pre-dried. Acrylamide was undetectable when crisps were pre-dried and vacuum fried at 110oC, 150 mbars. The crisps with pre-drying subsequent sugar dipping and vacuum fried at low temperature had improved color compared with the control samples, which were produced by conventional frying at high temperatures.
Note: Part 3 publication restricted due to copyright restrictions.

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Redman, Claire T. Petersen. "Factors affecting the composition and quality of broccoli juice : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Food Technology at Massey University, Palmerston North, New Zealand." 2009. http://hdl.handle.net/10179/1315.

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A shelf life trial using a fully balanced factorial experimental design was used to analyse the effects of acidity and light on broccoli juice made on a semi commercial scale over an eight week period in simulated retail refrigerated storage conditions. The research focused on making broccoli juice on a pilot scale, and what happens to the colour, composition and flavour during storage. A pilot scale production of pasteurised broccoli juice was conducted and the juice satisfied microbiological safety limits for the eight week shelf life trial in retail storage conditions. The stability of the green colour of fresh broccoli through processing and storage was assessed. Neutral broccoli juice remained green for four weeks before the colour became more yellow. The acidified juice became yellow on acidification and did not change significantly during storage. Dietary fibre and pectin levels did not change during storage. Chlorophyll and carotenoids levels decreased during storage and were directly influencing the colour changes in the juices. Ascorbic acid levels decreased significantly during processing resulting in low ascorbic acid levels (12 - 15 mg /100ml of juice) at the start of the shelf life trial and dropped further to 2-6 mg /100ml of juice after eight weeks. Acidification and storage in the dark had a protective effect on the degradation of ascorbic acid with only a 58% reduction in ascorbic acid levels compared to an 84% reduction in neutral light stored broccoli juice. The effect of processing and storage on the flavour of the beverage was assessed using a trained sensory panel providing descriptive analysis. The sensory profiles for neutral and acidified juices were extremely different with the unbalanced acidity suppressing the perception of the basic tastes, sweet, salty and bitter. The neutral juice sensory profile only changed slightly in aroma attributes during storage for seven weeks. The astringent aftertaste of the acidified juice increased while the broccoli smell decreased during storage. The results from this research indicate that the production of a broccoli juice with a yellow green colour and some retained nutritional components is achievable with a refrigerated (4 °C) shelf life of 30 days in light excluding glass packaging. The neutral juice is recommended as it was greener and had a broccoli flavour.A shelf life trial using a fully balanced factorial experimental design was used to analyse the effects of acidity and light on broccoli juice made on a semi commercial scale over an eight week period in simulated retail refrigerated storage conditions. The research focused on making broccoli juice on a pilot scale, and what happens to the colour, composition and flavour during storage. A pilot scale production of pasteurised broccoli juice was conducted and the juice satisfied microbiological safety limits for the eight week shelf life trial in retail storage conditions. The stability of the green colour of fresh broccoli through processing and storage was assessed. Neutral broccoli juice remained green for four weeks before the colour became more yellow. The acidified juice became yellow on acidification and did not change significantly during storage. Dietary fibre and pectin levels did not change during storage. Chlorophyll and carotenoids levels decreased during storage and were directly influencing the colour changes in the juices. Ascorbic acid levels decreased significantly during processing resulting in low ascorbic acid levels (12 - 15 mg /100ml of juice) at the start of the shelf life trial and dropped further to 2-6 mg /100ml of juice after eight weeks. Acidification and storage in the dark had a protective effect on the degradation of ascorbic acid with only a 58% reduction in ascorbic acid levels compared to an 84% reduction in neutral light stored broccoli juice. The effect of processing and storage on the flavour of the beverage was assessed using a trained sensory panel providing descriptive analysis. The sensory profiles for neutral and acidified juices were extremely different with the unbalanced acidity suppressing the perception of the basic tastes, sweet, salty and bitter. The neutral juice sensory profile only changed slightly in aroma attributes during storage for seven weeks. The astringent aftertaste of the acidified juice increased while the broccoli smell decreased during storage. The results from this research indicate that the production of a broccoli juice with a yellow green colour and some retained nutritional components is achievable with a refrigerated (4 °C) shelf life of 30 days in light excluding glass packaging. The neutral juice is recommended as it was greener and had a broccoli flavour.

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Zhang, Yin. "Packaging sterilization : aseptic filling technology : a report presented in fulfillment of the requirements for the degree of Master of Technology in Food Technology at Massey University." 2009. http://hdl.handle.net/10179/1374.

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Xenos Ltd. is a technology driven food company, that specializes in aseptic processing and packaging beverage products in bottles. Their aseptic filling technology is based on packaging sterilization with combined treatments of oxidizing agents and Ultraviolet radiation. Recent research studies have suggested that there is a synergistic effect of hydrogen peroxide (0.5 – 1 %) plus UV on inactivation of microorganisms including spores. Advantages of the combined treatment include rapid inactivation, minimum hydrogen peroxide residue in products, with the method being applicable to a wide range of packaging types. Based on this principle, a unique aseptic packaging technique has been developed by Xenos Ltd., which utilizes the combination of vaporized Perform (a commercial sterilizing agent manufactured by Orica Chemnet containing 25% hydrogen peroxide and 5% peracetic acid) and UV radiation at 7.5 – 12.5 W/m2. The aim of the project was to improve and validate the effectiveness of the packaging sterilization process through challenge tests. Challenge tests were conducted using Bacillus subtilis spores as the test microorganism to determine the log reductions delivered by the packaging sterilization system. The tests were firstly carried out on a pilot plant scale aseptic filling machine, in order to test the sterility of the small scale system, and investigate processing parameters (operational conditions) which could affect and improve sterility. The established operational conditions for achieving target sterility were used for designing and modifying an upgrade aseptic packaging system. Finally validation of the upgrade packaging sterilization system was conducted through challenge tests to prove sterility. It is highly recommended that in order to ensure sterility, the packaging sterilization system with vaporized Perform plus UV treatment must meet the requirements listed below during the sterilization process:  Hydrogen peroxide concentration of Perform condensate on bottles (after steaming) is best within 0.5 – 1 %;  Perform loading level should be minimum 300 mg/bottle after vaporized Perform treatment;  UV treatment time applied is greater than 2 seconds during UV treatment;  At least 20 seconds of penetration time (time between Perform treatment and UV treatment) should be allowed. The upgrade sterilization system used by Xenos Ltd. has been improved to meet the above operational conditions. With spore loading level of 106 per bottle and 105 per cap, the system is able to deliver at least a 6 log reduction of B. subtilis spores on PET or glass bottles and a 5 log reduction on bottle caps. Moruzzi et al. (2000) stated that at least a 4 log reduction is commercially required for an aseptic packaging process. Therefore, the system’s sterility would meet the commercial acceptable sterility.

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Teh, Koon Hoong. "Biofilm formation by Campylobacter jejuni in controlled mixed-microbial populations : a thesis presented in partial fulfillment of the requirements for the degree of Master of Technology in Food Technology at Massey University, Palmerston North, New Zealand." 2008. http://hdl.handle.net/10179/782.

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Poultry meat consumption in New Zealand has been increasing since 1975 with the highest peak reported in 2006. The total poultry meat consumption was 36.5 kg per capita in the year ending September 2006. Consumption of contaminated food with raw poultry can lead to campylobacteriosis, which is a food-borne disease that causes gastroenteritis in humans and it is a major problem in New Zealand. There were 12,776 reported cases of campylobacteriosis in 2007, which accounts for 65.9% of the overall notified diseases. Campylobacteriosis can lead to Guillain-Barré syndrome in some patients, an autoimmune disorder of the peripheral nervous system. Campylobacteriosis is caused by consumption of either Campylobacter jejuni or Campylobacter coli. Campylobacter spp. have been found in commercially raised poultry being infected predominantly by C. jejuni. C. jejuni has been found associated with biofilms of other bacterial species in the watering supplies and plumbing systems of animal husbandry facilities and animalprocessing plants. A biofilm is an assemblage of microbial cells that is associated with a surface and the cells are enclosed in a matrix of polysaccharides, which provides a survival advantage to the bacteria in the film. In this study, the ability to form biofilm was measured in a laboratory assay using microtitre plates. C. jejuni strains in monoculture were shown to attach to the abiotic surface and form biofilms to various degrees, thus potentially enhancing their survivability in the poultry environment. C. jejuni was also shown to have the ability to attach and survive in mixed-microbial populations. Biofilm formation may play a role in the epidemiology of C. jejuni infections. Enterococcus faecalis and Staphylococcus simulans may play a role in the biofilm formation in the poultry environment as both of these microorganisms were able to form, and harbour C. jejuni in their biofilms. Pseudomonas aeruginosa seemed to inhibit biofilm formation and C. jejuni in the mixed-microbial population. Further studies are required to establish control measures against the formation of biofilms containing C. jejuni in poultry processing plants and farms in New Zealand to reduce the reservoir of contamination and thus reduce the incidence of campylobacteriosis.

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21

Sarkar, Anwesha. "Behaviour of milk protein-stabilized oil-in-water emulsions in simulated physiological fluids : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand." 2010. http://hdl.handle.net/10179/1409.

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Emulsions form a major part of processed food formulations, either being the end products in themselves or as parts of a more complex food system. For the past few decades, colloid scientists have focussed mainly on the effects of processing conditions (e.g. heat, high pressure, and shear) on the physicochemical properties of emulsions (e.g. viscosity, droplet size distribution and phase stability). However, the information about the behaviour of food structures post consumption is very limited. Fundamental knowledge of how the food structures behave in the mouth is critical, as these oral interactions of food components influence the common sensorial perceptions (e.g. creaminess, smoothness) and the release of fat-soluble flavours. Initial studies also suggest that the breakdown of emulsions in the gastrointestinal tract and the generated interfacial structures impact lipid digestion, which can consequently influence post-prandial metabolic responses. This area of research needs to be intensively investigated before the knowledge can be applied to rational design of healthier food structures that could modulate the rate of lipid metabolism, bioavailability of nutrients, and also help in providing targeted delivery of flavour molecules and/or bioactive components. Hence, the objective of this research was to gain understanding of how emulsions behave during their passage through the gastrointestinal tract. In vitro digestion models that mimic the physicochemical processes and biological conditions in the mouth and gastrointestinal tract were successfully employed. Behaviour of model protein-stabilized emulsions (both positively charged (lactoferrin) as well as negatively charged [β-lactoglobulin (β-lg)] oil-in-water emulsions) at each step of simulated physiological processing (using model oral, gastric and duodenal fluids individually) were investigated. In simulated mouth conditions, oil-in-water emulsions stabilized by lactoferrin or β-lg at the interfacial layers were mixed with artificial saliva at neutral pH that contained a range of mucin concentrations and salts. The β-lg emulsions did not interact with the artificial saliva due to the dominant repulsion between mutually opposite charges of anionic mucin and anionic β-lg interfacial layer at neutral pH. However, β-lg emulsions underwent some depletion flocculation on addition of higher concentrations of mucin due to the presence of unadsorbed mucin molecules in the continuous phase. In contrast, positively charged lactoferrin emulsions showed considerable salt-induced aggregation in the presence of salts (from the saliva) alone. Furthermore, lactoferrin emulsions underwent bridging flocculation because of electrostatic binding of anionic mucin to the positively charged lactoferrin-stabilized emulsion droplets. In acidic pH conditions (pH 1.2) of the simulated gastric fluid (SGF), both protein-stabilized emulsions were positively charged. Addition of pepsin resulted in extensive droplet flocculation in both emulsions with a greater extent of droplet instability in lactoferrin emulsions. Coalescence of the droplets was observed as a result of peptic hydrolysis of the interfacial protein layers. Conditions such as ionic strength, pH and exposure to mucin were shown to significantly influence the rate of hydrolysis of β-lg-stabilized emulsion by pepsin. Addition of simulated intestinal fluid (SIF) containing physiological concentrations of bile salts to the emulsions showed competitive interfacial displacement of β-lg by bile salts. In the case of lactoferrin-stabilized emulsion droplets, there was considerable aggregation in the presence of intestinal electrolytes alone (without added bile salts) at pH 7.5. Binding of anionic bile salts to cationic interfacial lactoferrin layer resulted in re-stabilization of salt-aggregated lactoferrin emulsions. On mixing with physiological concentrations of pancreatin (mixture of pancreatic lipase, amylase and protease), significant degree of coalescence and fatty acid release occurred for both the emulsions. This was attributed to the interfacial proteolysis by trypsin (proteolytic fractions of pancreatin) resulting in interfacial film rupturing. Exchange of initial interfacial materials by bile salts and trypsin-induced film breakage enhanced the potential for lipolytic fractions of pancreatin to act on the hydrophobic lipid core. The lipid digestion products (free fatty acids and mono and/or diglycerides) generated at the droplet surface further removed the residual intact protein layers from the interface by competitive displacement mechanisms. The sequential treatment of the cationic and anionic emulsions with artificial saliva, SGF and SIF, respectively, was determined to understand the impact of initial protein type during complete physiological processing from mouth to intestine. Broadly, both the protein-stabilized emulsions underwent charge reversals, extensive droplet flocculation, and significant coalescence as they passed through various stages of the in vitro digestion conditions. Except in the simulated mouth environment, the initial charge of the emulsifiers had relatively limited influence on droplet behaviour during the simulated digestion. The results contribute to the knowledge of how structure and charge of the emulsified lipid droplets impact digestion at various stages of physiology. This information might have important consequences for developing suitable microstructures that allow controlled breakdown of droplets in the mouth and predictable release of lipids in the gastrointestinal tract.

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22

Nahid, Amsha. "Modeling heat transfer in butter products : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (Ph. D.) in Bioprocess Engineering, Institute of Technology and Engineering, Massey University, Palmerston North, New Zealand." 2007. http://hdl.handle.net/10179/1442.

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Butter keeping quality and pallet physical stability during transport and storage are dependent on the temperature distribution through the product. Understanding these temperature changes are of vital importance for the dairy industry with regard to butter manufacture, storage and shipping. Three dimensional mathematical models of heat transfer were developed to predict thawing and freezing in butter products. These models require accurate thermophysical data as an input. Specific heat capacity and enthalpy of butter with different composition was measured using Differential Scanning Calorimetry. The specific heat capacity of butter differs for cooling and heating operations due to significant supercooling and delayed crystallization of the fat fraction of butter at temperatures well below the equilibrium phase change temperature during cooling. This reduces the heat capacity for cooling relative to that for heating. Thawing of individual blocks of butter was accurately predicted by the conduction only model (no mass transfer limitations) with equilibrium thermal properties giving accurate predictions when the butter was completely frozen before thawing. For partially frozen butter the conduction model with the measured temperature dependent specific heat capacity data for unfrozen butter including melting of some of the fat fraction gave accurate predictions. For freezing it was observed that water in the butter supercools many degrees below its initial freezing point before freezing due to its water in oil structure. Experiments suggested that during freezing release of latent heat observed as a temperature rebound is controlled as much by the rate of crystallisation of water in each of the water droplets as by the rate of heat transfer. A conduction only model including water crystallization kinetics based on the Avrami Model predicted freezing in butter successfully. Simple models with equilibrium thermal properties and nucleation only kinetics (based on homogenous nucleation theory) or the sensible heat only model (no release of latent heat) gave poor predictions. The models for individual blocks were extended to predict heat transfer in butter pallets. A butter pallet contains product, packaging material and the air entrapped between the packaging and butter cartons. Measurements were made for freezing and thawing of full and half pallets at a commercial storage facility and in the University laboratory. Thawing and freezing in wrapped tightly stacked pallets was predicted accurately by the conduction only model with effective thermal properties (incorporating butter, packaging and air) estimated by the parallel model. For unwrapped tightly stacked or loosely stacked pallets there is potential for air flow between the adjacent cartons of butter. An alternative approach was developed which consisted of modeling the pallet on block by block basis using effective heat transfer coefficients for each surface. Different heat transfer coefficients were used on different faces of the blocks depending on the location of the block in the pallet. This approach gave good predictions for both unwrapped tightly stacked and loosely stacked pallets using the estimated effective heat transfer coefficients from the measured data. Further experimental and/or modelling work is required in order to develop guidelines for estimating effective heat transfer coefficient values for internal block face for industrial scenarios.

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23

Goh, Kelvin Kim Tha. "Isolation and characterisation of bacterial exopolysaccharides produced by Lactobacillus delbrueckii subsp. bulgaricus NCFB 2483 and Sphingomonas elodea ATCC 31461 : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand." 2004. http://hdl.handle.net/10179/1728.

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The aim of this study was to explore the characteristics of a non-gelling exopolysaccharide (EPS) obtained from Lactobacillus delbrueckii subsp. bulgaricus NCFB 2483 and a gelling EPS obtained from Sphingomonas elodea ATCC 31461 (31461). The EPSs were isolated from the two bacterial strains grown in milk permeate-based media. They were purified and then characterised using light scattering and viscometric techniques. A greater emphasis of this research was placed on 2483 EPS since its physical characteristics have not been reported to date. In the case of 31461 EPS. a model for gelation of the sodium gellan was proposed based on rheological and light scattering measurements. The rheological properties of the two EPSs were also compared with several commercial polysaccharides. Microscopy examination of 2483 EPS was carried out using confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). In CLSM, the lectin SBA (from Glycine max) Alexa Fluor 488 conjugate was used to stain the EPS since it has affinity for galactopyranosyl residues present in 2483 EPS. The CLSM micrographs showed a random distribution of EPS aggregates in the culture medium. At high magnification, the SEM micrographs showed web-like EPS structures. These structures were formed during the critical point drying process, when the EPS, which filled the interstices and channels of the protein aggregates, dehydrated. The 2483 EPS aggregates were found to be stable at neutral or low pH (~3.9) but were disrupted at high pH (pH 8-10). Procedures commonly used to quantify EPS from culture medium were found to be unreliable. In the development of an improved EPS assay, each of the processing steps was examined. Key improvements included the use of Flavourzyme for protein hydrolysis; optimising ethanol concentration to prevent lactose crystallisation yet allowing complete EPS precipitation; and a suitable centrifugation regime to minimise EPS loss. The improved EPS assay gave reproducible results (5% coefficient of variation). The isolation of 2483 EPS from milk media proved to be a difficult task because of interference from non-EPS components. An effective and simple approach allowing maximum EPS recovery involved the use of a hydrolysed milk medium which was ultrafiltered (UF) to remove molecular species larger than 2.5 x 105 Da. The UF permeate was suitable for the growth of 2483 with an EPS yield of ~400mg/L. Two EPS fractions (namely a soluble and an insoluble fraction) were isolated by ethanol precipitation and the soluble 'ropy' fraction was further purified to achieve ~98% purity. The elemental analysis of the purified fraction revealed the presence of nitrogen (~2.7% w/w). This could be due to the interaction of some peptides (from the growth medium) with the EPS. The polysaccharide composition of the soluble EPS fraction comprised of galactose, glucose, rhamnose and mannose residues (5:1:0.6:0.5). Traces of glucosamine were also found in the fraction. The purified fraction of 2483 EPS was characterised. Using a capillary viscometer, an intrinsic viscosity of ~2013mL/g was determined. The flow curves of the 2483 EPS solutions obtained using a rotational viscometer showed shear-thinning behaviour and an exponent value of ~0.76 (based on the Cross-type model) is typical of random coil polymers. The concentration dependence of the viscosity plot produced gradients of ~1.1 in the dilute domain and ~3.3 in the semi-dilute to concentrated domain. The coil overlap parameters at three concentration domains (c*[ŋ],ccr[ŋ] and c**[ŋ]) were 0.55, 2.86 and 5.67 respectively. The molecular parameters of the 2483 EPS were found via static light scattering measurements to have a weight-average molar mass (Mw.) of ~2 x 106 Da, a z-average root-mean-square radius ((r2g)z1/2) of ~165nm and a low polydispersity index (Mw/Mn ~1.15). The plot of Mw versus (r2g)z1/2 gave a gradient of approximately 0.5, which also suggested that the EPS polymer adopted a random coil conformation. The second part of the research involved gellan gum. Two gellan samples were studied. The first gellan sample was obtained from the fermentation of Sphingomonas elodea ATCC 31461 using milk permeate-based medium (31461). The second sample was a commercial high acyl gellan (LT100). Both gellan samples were converted to their sodium forms (Na-31461 and Na-LT100 gellan) using cation exchange resin and purified. The Na-gellan samples were highly sensitive to changes in Na+ concentrations. From oscillatory measurements, it was found that the complex moduli of the two Na-gellan samples superimposed closely at a specific Na+ concentration. The model for the conformational changes of Na-gellan molecules from a solution to a gel was proposed based on rheological and light scattering data. At very low Na+ concentrations (<19mM, in the case of Na-LT100). Na-gellan molecules were single-stranded (Mw ~2.5 x 10 5 Da) and adopted random coil conformation (exponent value based on the Cross-type model of ~0.76). At a slightly higher Na+ concentration (~19-24mM), Na-gellan molecules formed double-helices which led to a two-fold increase in molecular weight (M w ~5.2 x 105 Da). The double-stranded molecule appeared to be stiffer (exponent value of the Cross-type model ~0.82) and the mechanical spectra (G',G”) demonstrated 'weak ge' characteristics. A further increase in the Na+ concentration (>24mM) resulted in the formation of a gel network. The study also found that at low Na+concentration, both single-stranded and double-stranded Na-gellan molecules had a tendency to form aggregates under zero-shear conditions. The interactions involved in these aggregates were considered weak and transient, according to the Cox-Merz plot and light scattering data.

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Werner, Stephen R. L. "Air-suspension coating of dairy powders : a micro-level process approach : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Technology at Massey University, Palmerston North, New Zealand." 2005. http://hdl.handle.net/10179/1549.

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Air-suspension particle coating is a process by which thin coatings are applied to powder particles. The coatings can be formulated to act as permeable barriers to increase powder shelf-life or to impart controlled release character. The ultimate objective of a coating operation is to produce individual particles, each with a well-controlled, even coating. This project was focused on the air-suspension coating of fine powders of ~100 µm in diameter for the dairy industry. Despite the widespread use of the technology in the pharmaceutical industry, its use in the food industry has been limited. Little is known about the fundamental mechanisms, and so published work to date is product and equipment specific and is statistical in the way the experimental design and analysis has been approached. This 'black box' approach is time consuming and costly. Better methods based on an understanding of the physical and chemical mechanisms are needed to deal with the numerous products and constantly changing formulations typical of the dairy industry. This thesis proposes a new approach to air-suspension particle coating research. The basis of this 'micro-level process approach', is to deconvolute the complex coating process into smaller manageable parts based on classical physical phenomena for which descriptions already exist. The thesis identifies and develops an understanding of the key micro-level processes controlling coated product quality and process performance. Four were selected for further study: drying, droplet impact and spreading, and stickiness which encompasses the two key micro-level processes of droplet impact and adherence and inter-particle agglomeration. They were studied separately to deconvolute the variable effects and interactions. Kinetic data were collected for the drying droplets containing maltodextrins, whey protein isolate and gum arabic. A mathematical model, based on 'ideal shrinkage' was developed to predict the drying kinetics of single droplets with particular interest in the development of the surface glass transition temperature. The model accurately predicted the kinetics until significant morphological changes occurred in the droplet. To better predict the kinetics late in the drying process, the droplet radius was set to be constant at a time based on the surface proximity to the surface glass transition temperature (critical X concept). This was done to arrest droplet shrinkage in line with experimental observations and to more accurately depict the drying of high molecular weight, amorphous glass forming polymers. After this point, a new flexible calculation scheme was used to better predict the variation in internal droplet structure as either a dense, 'collapsed shell' structure or a 'dense skin-porous crumb' structure. Further study should focus on the surface and internal droplet structure (porosity and mechanical integrity) development during drying, particularly the conditions leading to the arresting of the droplet radius and the subsequent rate of skin thickness progression. The critical X concept was used to make industrial-scale predictions of the optimum drying conditions that ensure maximum droplet impact and adherence efficiency and minimum inter-particle agglomeration in a Würster-style coating operation. This enabled the prediction of two key design parameters, the nozzle distance from the powder impact point and the Würster insert height. The span in design parameters showed that there is significant opportunity for design optimisation based on the critical X concept. A probe tack test was used to map the level of stickiness of droplets of different coating materials as they dried. As skin formation progressed, the stickiness passed through a maximum, in most cases to arrive at a point at which the droplet was no longer sticky at all (non-adhesive state). The maximum point of stickiness represents the ideal state to ensure successful droplet-substrate impact and adherence. The minimum point of stickiness represents the ideal state to prevent unwanted inter-particle agglomeration. The time interval between the onset of stickiness and the non-adhesive state was particularly dependent on the addition of plasticisers, but also on the formulation and the drying air conditions. Future work should look to establish a possible relationship between the surface glass transition temperature and the probe tack test stickiness measurements. The impact and spreading of droplets containing maltodextrin DE5 on to solid anhydrous milkfat was studied using a high speed video camera. It was found that the final spread diameter was able to be fixed close to the maximum spread diameter by using surfactants, thus avoiding significant recoil. Because existing literature focuses on predicting the maximum spread diameter, this work defines a need for adequate prediction methods for the final spread diameter, as this is the significant parameter in coating applications. Formulation and operating guidelines were established to independently optimise each micro-level process. These were used in a series of population based coating experiments in a pilot-scale Würster coater. This study highlighted the limited flexibility of the standard 'off-the-shelf' Würster coating apparatus for the coating of fine sized dairy powders. Because of this, the validation of the guidelines were inconclusive and optimisation could not be carried out. Further validation work is required on a custom-built apparatus for dairy powders. This work has advanced the fundamental knowledge of the coating process and is independent of material, equipment and scale. This knowledge, based on physical and chemical mechanisms, can be used to develop coating formulations and identify optimum process conditions for successful coating in less time and at less expense than is current practice. The next step is to put the guidelines into practice and craft the engineering of a continuous coating apparatus for dairy powder applications.

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Patel, Hasmukh Ambalal. "Studies on heat- and pressure-induced interactions of milk proteins : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand." 2007. http://hdl.handle.net/10179/1606.

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The present study was aimed at understanding the high pressure (HP) processing-induced interactions of milk proteins in whey protein concentrate (WPC) solutions, in skim milk and in pure protein systems. The changes in milk proteins induced by heat treatments in the same systems under selected conditions were also evaluated. The main approach taken was to elucidate changes in the whey proteins in heat- and pressure-treated samples from common aliquots, under identical conditions, using various one-dimensional (1D) and two-dimensional (2D) polyacrylamide gel electrophoresis (PAGE) techniques in the absence or presence of a disulphide bond reducing agent. In some instances, the samples were also analysed using small deformation rheology, size exclusion chromatography (SEC) and transmission electron microscopy (TEM). The results of the present study indicated that, in general terms, heat treatment and HP treatment had common effects, i.e. denaturation and subsequent aggregation of whey proteins. Both heat treatment and HP treatment generated disulphide-bonded and hydrophobically bonded aggregates of whey proteins. However, the sensitivities of each of the whey proteins to heat treatment [immunoglobulin (Ig) > lactoferrin (LF) > bovine serum albumin (BSA) > β-laetoglobulin B (β-LG B) > β-LG A > α-lactalbumin (α-LA)] and pressure treatment (β-LG B > β-LG A > IgG > LF > BSA > α-LA) were considerably different. Also, HP treatment generated a comparatively greater proportion of smaller aggregates than did heat treatment. The effects of protein concentration, intensity of pressure treatment, holding time and pressurising temperature on whey protein aggregation in WPC solutions were investigated. The rate of aggregation of whey proteins increased with an increase in the concentration of protein in the WPC solution and the pressurising temperature. The combination of low protein concentration, mild pressure treatment (200 MPa) and low pressurising temperature (20°C) led to minimal loss of native-like and SDS-monomeric β-LG, whereas the combination of high protein concentration, severe pressure treatment (600 MPa) and higher pressuring temperature (40°C and higher) led to significant loss of both native-like and SDS-monomeric β-LG. The sensitivity of pressure-resistant whey proteins, such as α-LA and BSA, to the aggregation was significantly increased at pressurising temperatures of 40°C and higher. Self-supporting gels were formed when 8 or 12% (w/v) WPC solutions were pressure treated at 600-800 MPa. 20°C. Detailed analysis of the behaviour of the proteins during the formation of these gels revealed a novel pathway, suggesting that intermolecular disulphide bond formation occurred at high pressure but that hydrophobic association became important after the HP treatment. In the later part of the study, heat- and HP-induced interactions of caseins and whey proteins were studied in a more complex system, i.e. skim milk. With the application of modified PAGE techniques, it was possible to show that the high molecular weight disulphide-bonded aggregates that were formed by HP treatment of skim milk contained disulphide-linked complexes consisting of αS2-casein (αS2-CN) as well as κ-CN, β-LG and other whey proteins. The results showed that the effects of heat treatment and HP on the interactions of the caseins and whey proteins in milk were significantly different. The accessibility of αS2-CN and the formation of complexes involving αS2-CN, κ-CN and whey proteins in the HP-treated milk, as demonstrated using the modified 2D PAGE technique, and as explained by possible proposed reactions of the caseins and whey proteins in pressure-treated milk, was an important finding of the present study. Finally, a study on the effects of HP treatment in model systems using pure proteins in solution, both singly or in binary and ternary combinations, generated very useful information and clarified the role of each protein in pressure-induced aggregation and interactions of milk proteins in complex systems such as WPC and milk. It was found that the reactions of β-LG were not significantly affected by other proteins such as α-LA or BSA, but that the presence of β-LG in the system catalysed the reactions of other proteins such as α-LA or BSA.

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Evers, Jacobus Meindert. "Novel analytical techniques for studying the milk fat globule membrane : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand." 2008. http://hdl.handle.net/10179/1480.

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Video files: Some images may require stereoscopic glasses
Fat in milk and cream is present as tiny droplets, which are each enveloped in a thin membrane, called the milk fat globule membrane (MFGM). The MFGM can easily be damaged by factors such as pumping the milk and applying other forms of agitation. MFGM damage is believed to reduce processing efficiency and compromise the quality of manufactured products. A comprehensive review of the literature showed that our understanding of changes occurring in the MFGM post secretion of the fat globule by the mammary secretory cell is still rudimentary. Furthermore, it was found that a fundamental understanding of MFGM damage in raw milk is lacking. Hence, this study sought to develop analytical techniques for studying the MFGM. Fluorescent probes were identified that associated with the MFGM (bovine, ovine, human) in one of two ways: either by embedding in the phospholipid bilayer (lipophilic probe) or by binding to carbohydrate moieties of glycosylated chains in the glycocalyx (lectin probes). The use of these probes, in combination with either conventional fluorescence microscopy or confocal laser scanning microscopy, allowed 2-D images and 3-D images of fat globules to be made. Application of water-soluble lipophilic probes and the lectin wheat germ agglutinin (WGA) directly to milk allowed the staining of the MFGM in its native environment. Variable distribution patterns of the probes in the MFGM were observed, which suggests that the MFGM of fat globules in harvested milk is structurally and chemically heterogeneous both within and among globules from the same species and between species, and even among fat globules within the milk of an individual animal. Furthermore, the binding behaviour of WGA to the MFGM of native fat globules (in bovine milk) and washed fat globules (in model systems) following heat treatment implicated β-lactoglobulin, α-lactalbumin, immunoglobulin M and/or the glycosylated proteins Periodic acid Schiff 6/7 in the disappearance of fat globule aggregation upon elevated heat treatment of milk. The results of the current study showed that the use of membrane-specific fluorescent probes, particularly in combination with confocal laser scanning microscopy, has significant potential for providing real time structural and chemical information about the MFGM in matrices such as harvested milk and milk products. In addition to the fluorescence microscopy techniques, development of other techniques was also conducted. Flow cytometry was shown to have significant potential for the quantitative determination of various properties of fat globules and their membranes. Although no suitable sample preparation technique could be developed in this study, atomic force microscopy is believed to have significant potential for studying structural and physical properties of the MFGM. Selective harvesting of individual fat globules was shown to be possible by using a micromanipulator. In future work, this technique is expected to be used in combination with fluorescence microscopy, or atomic force microscopy. The present study has shown that the development and application of novel analytical techniques has advanced, and in the future will further advance, understanding of the MFGM.

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Overington, Amy Rachael. "Concentration of dairy flavours using pervaporation : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Auckland, New Zealand." 2008. http://hdl.handle.net/10179/1389.

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The food industry could potentially benefit from using pervaporation, a membrane process, to concentrate flavours. This research aimed to investigate its application for concentrating flavours in dairy process streams. Pervaporation experiments were carried out at a range of operating conditions, using hydrophobic membranes. The feed mixtures were either aqueous model solutions of dairy flavour compounds (acids, esters and ketones), complex model mixtures containing flavour compounds plus non-volatile dairy components, or real dairy products. Flavour compound enrichment factors ranged from below one to above 30, with esters and ketones being concentrated more effectively than acids. Thus, the flavours could be partially fractionated based on their chemical structure. The permeation of acids was reduced by approximately 50% when the feed pH was increased to near their p Ka values. For flavour compounds with lower molecular weights than approximately 1 20 g mol- I , permeation was controlled mainly by sorption i n the membrane; for larger compounds it was controlled mainly by diffusion through the membrane. The mass transfer of each flavour compound increased with temperature, following an Arrhenius-like relationship. The activation energy was a function of each compound's heat of sorption, its molecular weight, and the elastic modulus of the membrane. The activation energy was also related to the Arrhenius preexponential factor. Thus, fluxes could be estimated through empirical correlations. The non-volatile feed composition was an important factor influencing the pervaporation performance. Milk protein isolate (4% w/v) or lactose (6% or 1 2% w/v) bound with the flavour compounds in the feed, thus lowering the enrichment of sorption-controlled compounds. Milk fat (up to 38% w/v, in the form of cream ) reduced the enrichment of all the flavour compounds tested. Esters and ketones became unavailable for pervaporation as they partitioned into the fat phase; acids remained mainly in the aqueous phase, but their permeation was reduced because the added cream increased the feed pH. Experiments with real dairy products showed that pervaporation could be used to concentrate diacetylin starter distillate, and to selectively recover short-chain esters from ester cream. Of these two products, starter distillate is the more promising for use as a pervaporation feed stream.

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28

Trinh, Binh. "Rheological characterisation of age thickening in milk concentrates : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Engineering at Massey University." 2006. http://hdl.handle.net/10179/1559.

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Pages A58-A66 are missing from original but content appears complete.
This project investigates the time-dependent rheological behaviour of fresh and reconstituted milk concentrates. New experimental protocols, including sampling and measurement techniques, as well as equipment calibration and data analysis procedures were developed for both the industrial surveys and controlled rheology experiments. The controlled rheology experiments were mainly carried out on reconstituted milk concentrates to minimise the variation in composition of fresh milk. A new recombination rig was built which could minmise the age thickening process by mixing at 35°C and recirculating at 40,000 s-1 to break down the structure completely. This is the essence of this project, where age thickening is studied from a starting point of a filly broken down structure in contrast to past research. Using this method, the replicate milk concentrate samples had reproducible rheological behaviour, with a maximum reproducible error of 10%. Age thickening involves two stages, a slow initial increase in apparent viscosity with storage time, followed by a sudden sharp rise which marks the onset of gelation. The age thickening behaviour of milk concentrates is dependent on the processing variables prior to rheological measurement. These include solids content, shear rate and temperature during recombination, shear rate and residence time in the plate heat exchanger, and most importantly the raw material. The viscosity at the gelling point is an important characteristic of the age thickening process, and seems to depend mainly on the powder used, rather than the process treatments applied. Industrial surveys exhibited similar trends, even under varying conditions that could not be completely controlled. It is proposed that two types of age thickening phenomena can be distinguished: type I occurs below the temperature at minimum viscosity (65°C in this case), where weak interactions take place between the casein micelles; type II occurs above the temperature at minimum viscosity, where additional stronger covalent bonds are formed, primarily due to the denaturation of whey proteins. No mathematical model for the time-dependent rheology was developed. However, some important issues that must be taken into account during modelling were discussed. The results showed that the age thickening process is more complex than had previously been envisaged. The knowledge of the interactions between the operating conditions, rheology of fresh concentrates and powder properties should be invaluable in the improvement of plant efficiency and quality control.

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29

Kühn, Janina. "Studies on interactions of milk proteins with flavour compounds : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand." 2007. http://hdl.handle.net/10179/1426.

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Milk proteins are known to bind volatile flavour compounds to varying extents, depending on the nature of the protein and flavour compound. Processing conditions, such as temperature and pH, are also known to have an influence on the interactions between milk proteins and flavour compounds. These interactions cause a great challenge for flavour scientists because they influence the perceived aroma profile of food products significantly, in particular in low-fat food products. The objectives of this research were to develop a headspace solid-phase microextraction (SPME) method followed by gas chromatography with flame ionisation detection (GC-FID) for the investigation of protein-flavour interactions, and to determine binding parameters of the hydrophobic flavour compound, 2-nonanone, to individual milk proteins - namely, β-lactoglobulin (β-lg), α-lactalbumin (α-la), bovine serum albumin (BSA), αs1-casein, and β-casein -, whey protein isolate (WPI), and sodium caseinate. Secondly, it was the aim to compare the binding of the structurally similar flavour compounds - 2-nonanone, 1-nonanal, and trans-2-nonenal – to WPI in aqueous solution, and to investigate the effect of heat and high pressure treatment, and pH on the extent of protein-flavour binding. The final objective was to investigate the in vivo release of the reversibly bound flavour compound, 2-nonanone, from WPI and sodium caseinate using proton transfer-reaction mass spectrometry (PTR-MS), and to understand the effect of viscosity on flavour release in vivo. The binding of the model flavour compound 2-nonanone to individual milk proteins, WPI, and sodium caseinate in aqueous solutions was investigated, using headspace SPME followed by GC-FID. The 2-nonanone binding capacities decreased in the order: BSA > β-lg > α-la > αs1-casein > β-casein, and the binding to WPI was stronger than the binding to sodium caseinate. All proteins appeared to have one binding site for 2-nonanone, except for BSA which possessed two classes of binding sites. The influence of heat treatment, high pressure processing and pH of the protein solutions on the binding of 2-nonanone, 1-nonanal, and trans-2-nonenal to WPI was determined. The binding of these compounds to WPI decreased in the order: trans-2-nonenal > 1-nonanal > 2-nonanone. The binding of 2-nonanone appears to involve hydrophobic interactions only, whereas the aldehydes, in particular trans-2-nonenal, also react through covalent binding. Upon both heat and high pressure denaturation, the binding of 2-nonanone to WPI decreased, the binding of 1-nonanal remained unchanged, while the binding of trans-2-nonenal increased. The binding affinity of the flavour compounds and WPI increased with increasing pH, which is likely to result from pH dependent conformational changes of whey proteins. The in vivo flavour (2-nonanone) release from solutions of WPI and sodium caseinate was investigated using proton-transfer-reaction mass spectrometry. During consumption, 2-nonanone was partly released from WPI, whereas there was no significant release from sodium caseinate. Even after swallowing of the samples, a substantial amount of flavour was detected in the breath, suggesting that the milk proteins interact with the mucosa in the mouth and throat, resulting in a further release of flavour from mucosa-bound proteins. An increase in viscosity of the protein solutions by the addition of carboxymethylcellulose enhanced the release of 2-nonanone from WPI, and resulted in 2-nonanone release from sodium caseinate. This may be due to a thicker coating of the mucosa with the sample solution after swallowing due to the higher viscosity, resulting in additional release of protein-bound flavour. These findings contribute to the knowledge of the interactions that occur between flavour compounds and proteins, which is required to improve food flavouring and to make protein based foods, e.g., low-fat dairy products, sensorily more acceptable to the consumer. The results also emphasize a careful choice of food processing conditions, such as temperature, high pressure or pH to obtain a desirable flavour profile.

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Palmer, Jon Stuart. "Surface characteristics of an adhesive thermophilic spore-forming Bacillus, isolated from milk powder : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand." 2008. http://hdl.handle.net/10179/1384.

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The growth of thermophiles during the manufacture of milk powder leads to a progressive increase in the number of thermophilic bacteria contaminating the final product. The limited residence time of the milk in the plant during milk powder manufacture and the concentration effect of converting milk into milk powder cannot explain the number of thermophiles found in the final product. This suggests that thermophiles are attaching to the large surface area of stainless steel found within a milk powder plant and then growing and developing into biofilms, with individual cells and/or biofilm fragments sloughing off into the product line and thus contaminating the final product. The aim of the present study was to investigate the attachment mechanisms that enable the thermophile Anoxybacillus flavithermus (B 1 2) to attach to stainless steel surfaces. Passing a B 1 2 culture through a column of stainless steel chips, collecting the first cells to pass through, re-culturing and repeating the process six times, resulted in the isolation of a mutant, labelled X7, with lO-fold reduced ability to attach to stainless steel as well as a reduced ability to attach to plastic and glass. A comparison of bacterial cell surface properties indicated that X7 was less hydrophobic than its parental strain B 1 2 . Cell surface charge measurements also suggest that X7 has less net negative surface charge. Disruption of extracellular polysaccharides and DNA appeared to have no effect on the attachment process. Removal of surface proteins caused a reduction in attachment of B 1 2 and X7 as well as a reduction in surface hydrophobicity suggesting surface protein involvement in both. Analysis by two-dimensional gel electrophoresis of lysozyme/mutanolysin extracted surface proteins revealed two proteins expressed at reduced levels in X 7 compared with B 1 2 . One protein was identified by mass spectrometry as the cytoplasmic enzyme Formate acetyltransferase. The role of Formate acetyltransferase and the second unidentified protein on the attachment process of Anoxybacillus flavithermus remains unclear.

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31

Lu, Guangjin. "A novel approach for controlling foodborne pathogens using modified atmosphere and Lactobacillus reuteri DPC16 : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Albany, New Zealand." 2007. http://hdl.handle.net/10179/746.

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The current trend of increasing demand for minimally processed food requires more effective preservation technologies than are presently used. In this study, an investigation has been made into a novel strategy to control some common foodborne pathogens, and therefore, to provide an alternative means for enhancing the safety and extending the shelf lives of food products. Modified atmosphere is able to extend the shelf life of seafood and meat products. In this study, a simulated controlled atmosphere (CA) broth system was used to investigate the potential of a modified atmosphere rich in CO2 at a concentration of 40%, supplemented with N2, to control common foodborne pathogens, such as Listeria monocytogenes, Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, Staphylococcus aureus and Vibrio parahaemolyticus. Controlled atmosphere significantly reduced the exponential growth rates of all tested pathogens, while the effects on other growth parameters (eg. lag phase duration and maximum population density) depended on the individual species and the specific growth conditions. The CA significantly extended the lag phase durations of S. aureus and V. parahaemolyticus at 20 degrees C at both pH 6.3 and 6.8, and that of L. monocytogenes at both 7 degrees C and 20 degrees C, and at both pH 6.3 and 6.8. The CA also significantly lowered the maximum population densities of S. aureus and V. parahaemolyticus at 20 degrees C, at pH 6.3 and 6.8, S. Typhimurium at pH 6.8, and L. monocytogenes at pH 6.3 and 7 degrees C. E. coli O157:H7 and S. Typhimurium were more resistant to the inhibitory effect of the CA, while S. aureus and V. parahaemolyticus were most sensitive. The inhibitory effect of CA was due mainly to the extensions of the lag phase duration and the reduction of the exponential growth rates of the test pathogens. This study confirms other studies that CA as a means for food preservation provides potential to control foodborne pathogens and therefore enhance the safety of a food product. The use of lactic acid bacteria (LAB) in controlling spoilage microorganisms and pathogens in foods has been a popular research theme worldwide. In this study, the antimicrobial effects of 18 lactic acid bacteria strains were evaluated in vitro, with emphasis on the most effective strain, the newly characterised Lactobacillus reuteri DPC16. The results demonstrated antagonistic effects of many strains against L. monocytogenes, E. coli O157:H7, S. Typhimurium and S. aureus. L. reuteri DPC16 showed the strongest antimicrobial activity against the tested pathogens including both Gram-positive and Gram-negative bacteria. Co-cultivation of L. reuteri DPC16, and co-incubation of its spent culture supernatant (DPC16-SCS), with the pathogens have demonstrated that the antimicrobial effect is bactericidal and valid at pH 4 - 6.5 and at a temperature as low as 10 degrees C. Further characterisation of the antimicrobial effect of L. reuteri DPC16 showed it to be mainly due to the presence of reuterin (ß-hydroxypropionaldehyde), although lactic acid may have also played a role. These characteristics of L. reuteri DPC16 and its metabolite reuterin make it an unique and potent candidate as a biopreservative to control both Gram-positive and Gram-negative bacteria in foods. The combination of L. reuteri DPC16 and CA was assessed for its inhibitory effect on L. monocytogenes using DPC16-SCS and the fermentative supernatant of L. reuteri DPC16 from a glycerol-water solution (DPC16-GFS). The results showed that both of these supernatants, at 25 AU/mL, in combination with CA (60% CO2:40% N2) had a combined inhibitory effect on L. monocytogenes which could not be achieved by any one of the individual factors alone. Analysis of the levels of expression of some stress response genes of L. monocytogenes, after growth in the presence of L. reuteri DPC16 supernatant and/or CA, showed that the expression of some genes was affected including genes betL, gbuA and opuCA responsible for osmosis adaptation and genes gadA, gadB and gadC responsible for acid tolerance. Induction of gbuA, gadB and gadC by the culture supernatant suggests activation of osmotic and acid adaptation and that these genes play a major role in the culture supernatant-induced stresses. An investigation was also carried out to determine if the changes in gene expression conferred a cross-protection to heat. The result showed that the survival of L. monocytogenes grown in the presence of the culture supernatant and CA was significantly increased after exposure to heat treatment at 56oC, suggesting that a cross-protection to thermal stress had been induced. Based on these findings it is proposed that a comprehensive novel strategy incorporating both L. reuteri DPC16 or its fermentative products and a modified atmosphere rich in CO2 could be developed to potentially control foodborne pathogens in food products.

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32

Mossop, Nicholas Paul. "Bioactive extracts of Olea europaea waste streams : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Food Technology at Massey University." 2006. http://hdl.handle.net/10179/789.

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The production of olive oil has seen an increase in recent years due to a broader understanding of the health benefits of the Mediterranean Aliment Culture. With this expanding industry we also see an increase in the waste products associated with olive oil production. Given the high polluting content of the waste streams and the economic costs associated with its removal and processing, waste remediation and disposal has become a significant point of interest for both producers and local bodies. In this project, wastes of the olive oil production industry are examined for their use as the raw material for a novel product used in the control of horticulturally important diseases, examining the effect of extraction protocols on the activity of the final product. Active fractions of the olive oil wastes were identified from literature and protocols for their extraction and recovery developed; incorporating both standard solvent extraction and novel ultrasound-assisted extraction. Criteria for the analysis of extract quality were outlined and potential target applications identified. The biophenolic compounds of olive wastes were identified as providing the majority of the active fraction, so protocols were developed for the recovery of these compounds. Standard solvent extraction and ultrasound-assisted extraction were examined for their effectiveness of biophenolic recovery and their effect on product quality. Certain horticulturally important diseases were identified as potential targets, and bioassays undertaken to determine the ability of a crude extract to inhibit and control these diseases. It was found that the action of ultrasound during extraction provides a greater degree of recovery of biophenolic compounds, with minimal loss of product quality; as determined by bioassays and total biophenol determination. This increase in recovery is due primarily to the destruction of cellular material resulting in higher rates and absolute yields of recovery. This work provides evidence of the occurrence of some interesting phenomenon in the recovery of biophenols from olive wastes that deserves further examination. The crude olive leaf extract was shown to have an inhibitory effect on bacteria and effectively no inhibitory effect on fungal species in the total biophenol ranges tested. Erwinia amylovora and Staphylococcus aureus both showed a large susceptibility to the olive leaf extract. Results showed a higher degree of susceptibility of Gram positive bacteria and a potential resistance in soil microbes. For bacterial species, total biophenol concentrations of 0.15 to 3.50 mg GAE/ml provided inhibitory effects, while with the fungal species tested, no inhibitory effects were found at total biophenol concentrations of up to 2.50 mg GAE/ml. Some evidence exists that there is an opportunity for the economic recovery of olive biophenols for use as a novel product, but more work is required to determine specific applications and/or targets of use, as well as optimisation of the extraction and purification protocol. A sample removed from interfering compounds will allow the examination of activity of particular compounds and hence a better understanding of the action of the olive waste extract.

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33

Williams, Anna M. "Instant milk powder production : determining the extent of agglomeration : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemical Technology at Massey University, Palmerston North, New Zealand." 2007. http://hdl.handle.net/10179/1439.

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Agglomerated milk powders are produced to give improved properties such as flowability, dispersibility, reduced dustiness and decreased bulk density. A key function of these powders is to dissolve "instantly" upon addition to water and because of this they are also called "instant milk powders". They are produced by agglomerating the undersized fines that are returned to the top of the spray drier with milk concentrate droplet spray. Interaction occurs in a collision zone, often with multiple sprays and fines return lines. Agglomeration can be a difficult process to control and operators find it hard to fine tune the process to produce specific powder properties. This work aimed to understand the effects of key droplet and fines properties on the extent of agglomeration to allow a mechanistic understanding of the process. Three scales of spray drier were investigated in this study with different rates of evaporation; a small scale drier (0.5 - 7 kg water h-1), a pilot scale drier (80 kg water h-1) and a range of commercial production scale driers (4 - 15 000 kg water h-1). A survey of operators of commercial scale driers showed that control of instant milk powder production to influence bulk density is highly intuitive. Fines recycle rates were expected to be important in control of agglomeration processes and were estimated on a specific plant by using the pressure drop measured in the fines return line. A model based on pressure drop along a pneumatic pipeline under-predicted the experimental values for pressure drop due to solids, which means a calibration curve should be generated for each specific drier. Fines recycle rates were predicted to be significantly higher at 95 to 130 % of production rates compared to those expected by operators of 50%. Experimental measurements agreed with existing models for the effect of temperature on the density and viscosity of milk concentrates. Experimental results showed that the surface tensions of concentrated milks were within the same range as literature values for standard milks below 60°C, but were significantly higher for milk above 60°C. This is thought to be linked to the mechanism of skin formation due to disulphide cross linking at high temperatures and concentrations. Powder properties were also established for selected products produced on the commercial scale driers. These powders were then used in experiments on the two smaller driers. Because collision frequency depends on the velocity and droplet size of sprays; these properties were measured for the small scale drier and estimated, where possible, for the pilot and commercial driers. The small scale agglomerating spray drier was configured to alter droplet and particle properties when interacting a vertical fines particle curtain with a horizontal spray sheet. An extensive design and improvement process was carried out to ensure the system consistently delivered these streams in a controllable manner. The processes of collision and adhesion occur very quickly inside the spray drier. In order to assess the extent of agglomeration that has occurred, the feed streams must be compared to the final product stream. An ideal way to do this is to use an agglomeration index which compares the particle size distributions of the feed (fines recycle and spray streams) and the particle size distribution of the product stream (the agglomerated powder). The index described changes between these steams across the particle size distribution and is called an agglomeration efficiency, ξg. However, it was found that the presence of fines in the product of the one-pass design obscured the agglomerates formed. The agglomeration efficiency, ξg, was modified to become ξh which subtracted the fines stream from the agglomerated product distribution. In this way ξh models industrial operation where the fines are recycled, by effectively just comparing the spray and product streams entering and leaving the process. The small scale drier was used for an experimental study on natural and forced agglomeration, where the drier was operated with spray only, then with spray and fines. For natural agglomeration, SEM images of the product powder indicated that little agglomeration occurred between spray droplets. The product yield was unacceptably low (~ 40%) due to adhesion of spray droplets to the drying chamber wall opposing the horizontal spray. When the fines curtain was introduced in the forced agglomeration experiments, product yield increased above 50% because the fines acted as collectors for the spray droplets. However, the agglomeration performance of the modified spray drier was lower than expected. The equipment design was then optimised by considering three key issues; fines dispersion, droplet dispersion and stickiness, and agglomerate breakdown. Final experiments studied agglomeration at low fines to spray mass flux ratios and showed that increasing the fines size had a positive effect on agglomeration efficiency,ξh. The agglomeration study at pilot scale identified the effect of key variables, total solids, concentrate and fines flow rate, and fines size on the agglomeration efficiency. A dimensionless flux approach was used to explain the experimental results. The fines to spray mass flux ratio and the projected area flux ratio (at constant concentrate flow rate) were found to be the most suitable to represent the physical processes during agglomeration. Experimental results showed that a higher dimensionless flux resulted in more agglomeration and as well as small fines size and atomising low solids concentrate. The critical Stokes number highlighted the importance of particle size and collision velocity on the outcome of the collision as well as the importance of stickiness on adherence following the collision. A statistical analysis established a relational model for predicting the agglomeration efficiency based on fines size, total solids and the fines to spray mass flux ratio. This thesis has gained insight into agglomeration processes during spray drying and knowledge about how to define the extent of agglomeration. Practical findings from this research can have a significant impact on successful spray drying operation for instant powders. There are some practical steps to be taken industrially to promote the control of agglomerating spray driers. The first step is to measure and control the flow of fines recycled to the top of the spray drier. The next step is to validate the findings at industrial scale and link the agglomeration index to the bulk powder properties. However, there are many challenges that remain to be tackled in the area of milk powder agglomeration. Milk powder agglomeration at the top of the spray drier is a complex process involving many different variables. A more detailed study of the micro processes that occur during agglomeration will give increased understanding of the relationships between key operating variables and agglomerate properties.

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34

Smale, Nicholas John. "Mathematical modelling of airflow in shipping systems : model development and testing : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand." 2004. http://hdl.handle.net/10179/1718.

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Content removed due to copyright restrictions: Smale, N.J. Tanner D.J., Amos N.D., Cleland D.J. (2003). Airflow properties of packaged horticultural produce - a practical study. Acta Horticulturae, (599), 443-450
Horticultural exports are of economic significance to New Zealand. Only through providing consistently high quality products to distant markets can New Zealand hope to command a premium price. New Zealand's two major horticultural exports, apples and kiwifruit, are transported to foreign markets by sea; either in refrigerated holds on-board cargo vessels or in refrigerated containers. Long transit times mean that conditions in these systems must be carefully controlled to ensure high quality product arrives at market. Effective distribution of air is a key consideration in transport systems. A mathematical model to describe the flow of air in marine transport systems was developed. The model was based on a resistance network framework, relying on simplification of the complex geometry within the refrigerated space to a discrete number of flow paths and points of convergence and divergence. Correlations quantifying the flow resistance of each channel were required. Some of these correlations were already available, and some were developed specifically for this purpose. A general method for predicting the flow resistance of enclosed conduits based on the Darcy-Weisbach, laminar and Colebrook equations was found to be sufficiently accurate for use. The flow resistance of horizontally vented horticultural packages was quantified and the cause of the flow resistance investigated. Entrance and exit effects were found to be significant, and a relationship between vent size and flow resistance was developed. Air interchange between a vented carton and the general refrigerated space was shown to be a significant mode of heat transfer. The effect of vent design on the rate of air interchange was found to be complex. Quantitative relationships between vent characteristics and rates of air interchange could not be developed; however, some general observations were made. Vent size, aspect ratio and alignment were all found to affect the rate of interchange. An existing method for determining in-package fluid velocities was refined to improve the accuracy of data and reduce the measurement time. A low-cost method for measuring airflows in transport systems was also developed utilising thermistors. These thermistor anemometers were used to monitor velocities in four shipments of fresh produce from New Zealand. Three of the four vessels monitored showed large variation in the circulation rate in the period between evaporator defrosts due to frosting. In some cases, frosting was severe enough to cause loss of delivery air temperature control. Management of defrosts was identified as an area of improvement in refrigerated hold management. Validation of the model developed was performed using four systems: a laboratory scale test-rig, a 40' container and two of the surveyed refrigerated holds. Airflow predictions were used with a heat transfer model to predict in-package temperatures. Comparison of measured and predicted flows and in-package temperatures showed good agreement given uncertainty of geometry and input data. The implications of altering a number of operational and design variables in both containers and refrigerated holds were investigated using the developed models. Increased circulation rates were found to increase cooling rates and reduce temperature variability in both types of systems; however, the magnitude of the benefit decreased with increasing circulation rate. Removal of the floor gratings and the use of pallet bases as an air distribution channel was found to increase temperature variability in both types of systems. The magnitude of the increase was small in a 40' container but substantial in a refrigerated hold. The correlations and models developed in this thesis provide useful tools to analyse and optimise the design and operation of refrigerated marine transport systems.

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Anderson, Rachel C. "Antimicrobial peptides isolated from ovine blood neutrophils : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Biotechnology at Massey University, Palmerston North, New Zealand." 2005. http://hdl.handle.net/10179/1525.

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Content removed due to copyright restrictions: Anderson, R.C., Wilkinson, B. & Yu, P.L. (2004). Ovine antimicrobial peptides: new products from an age-old industry. Australian Journal of Agricultural Research, 55(1),69-75. Anderson, R.C. & Yu, P.L. (2003). Isolation characterisation of proline/arginine-rich cathelicidin peptides form ovine neutrophils. biochemical and biophysical research communications 312(4), 1139-1146. Anderson, R. C., Hancock, R.E.W. & Yu, P.L. (2004). Antimicrobial activity and bacterial membrane interaction of ovine-derived cathelicidins. Antimicrobial Agents and Chemotherapy, 48(2), 673-676. Anderson, R.C., Haverkamp R. & Yu, P.L. (2004). Investigation of morphological changes to S. aureus induced by ovine-derived antimicrobial peptides using TEM and AFM. FEMS Microbiology Letters, 240(1), 105-110. Anderson, R.C. & Yu, P.L. (2005). Factors affecting the antimicrobial activity of ovine-derived cathelicidins against E. coli 0157:H7. International Journal of Antimicrobial Agents 25, 205-210
The aim of the research presented in this thesis was to investigate the properties of the antimicrobial peptides found in ovine blood, in order to assess their potential as a high-value product. Due to the large number of lambs and sheep that are slaughtered New Zealand (approximately 25 million lamb and 5 million sheep per year), there are considerable volumes of ovine blood available for processing (approximately 40 million litres per year). Currently this blood is dried and sold as a low value product. The first objective of this research was to purify and characterise the antimicrobial peptides isolated from ovine neutrophils. A number of proline/arginine-rich peptides, as well as two small fragments of larger proteins, that displayed antimicrobial activity were identified. The second objective of this research was to investigate the mechanism of action of ovine antimicrobial peptides. For this investigation, three ovine peptides, α-helical SMAP29 and proline/arginine-rich OaBac5mini and OaBac7.5mini, were synthesised. Of these, SMAP29 was the most potent. The three peptides all bound Gram-negative bacterial LPS and caused the outer membrane to be permeabilised. SMAP29 caused significant depolarisation of the cytoplasmic membrane that led to cell lysis. However, the other two peptides only caused slight depolarisation of the cytoplasmic membrane, which indicates that they probably passed through the membrane to interact with the inner cellular contents. The third objective of this research was to investigate the morphological changes to bacterial cells induced by the ovine antimicrobial peptides. Transmission electron microscopy and atomic force microscopy confirmed that SMAP29 caused significant damage to the membranes of bacterial cells and induced cell lysis; whereas, OaBac5mini caused minor alterations to the bacterial membranes but did not induce cell lysis. The fourth objective of this research was to determine the effect of the environmental conditions on the activity of the peptides. The peptides were very stable over a range of pH values and when heated to temperatures up to 80°C. The activity of the peptides decreased slightly in the presence of monovalent cations and was inhibited by the presence of divalent cations. The peptides were significantly more active in combination than individually, and they were strongly synergistic with polymyxin B, a peptide antibiotic. The final objective of this research was to develop a pilot-scale extraction process for the isolation of antimicrobial peptides from ovine blood. The laboratory-scale process was simplified and adapted to design a process that could be used industrially. The crude pilot-plant extract was active against a broad-range of food pathogens and disease causing organisms. The antimicrobial peptides found in ovine blood have the potential to be used as biopreservatives for chilled lamb products, or in a topical cream for cuts and grazes; therefore it is recommended that further research is carried out to investigate the above applications and. if successful, the feasibility of commercialising the technology.

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Mcleod, Jeremy. "Nucleation and growth of alpha lactose monohydrate : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Process Engineering at Massey University." 2007. http://hdl.handle.net/10179/1444.

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Lactose represents approximately one third of the total solids in bovine milk. In the dairy industry, lactose is recovered from whey and whey permeates using a crystallisation process that involves both evaporation and a cooling stage. A good understanding of the lactose crystallisation kinetics enables both these processes to be operated at conditions that maximise the yield and minimise capital and processing costs. This study has looked at the nucleation and growth kinetics of the lactose crystallisation process. A model has been produced that can accurately predict the changing concentration profile as lactose is removed, via growth, from an industrial solution. This model incorporated the available literature information and expanded on it where required. The primary nucleation of alpha lactose monohydrate was investigated on the laboratory scale. The work identified the changing relationship, which occurs with increasing supersaturation, as lactose nucleation moves from being dominated by the heterogeneous mechanism to the homogenous mechanism. The absolute supersaturation at which the mechanism changes was found not to be affected by the solution temperature and agitation rate; however the presence of impurities lowered the supersaturation required for homogeneous nucleation. The effect of mixing on the primary nucleation rate was studied in a Rushton turbine agitated vessel and through a Venturi. Increasing the agitation rate increased the frequency of activated molecular collisions but the critical nucleus size remained constant. A strong correlation was found, for both mixing systems, between the nucleation rate and the frequency of vortex shedding.

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37

Das, Shantanu. "Biochemical characterisation of dairy yeasts and their application in cheese as anaerobic adjunct cultures : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand." 2004. http://hdl.handle.net/10179/1721.

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Yeasts are traditionally used as part of the surface microflora in surface-ripened cheeses, where they contribute positively to the flavour of the cheese. The primary objective of this study was to investigate the potential of three dairy yeasts to provide attributes as adjuncts in anaerobically ripened cheeses. Geotrichum candidum (B9001), Yarrowia lipolytica (B9014) and Candida kefyr (B9006), obtained from the Fonterra Co-operative Group Ltd, Palmerston North, New Zealand, were studied. They showed diverse metabolic activities in laboratory media, which were influenced by the growth conditions. The metabolic activities of special interest were the lipase and proteinase activities and the production of volatile compounds, as these are important for cheese ripening and flavour development. Lipase activity (p-nitrophenyl butyrate assay) and proteinase activity (fluorescein isothiocyanate β-casein assay) were determined in three fractions prepared from yeast cultures and designated as extracellular fraction, washed-cell fraction and intracellular fraction. Lipase activity of G. candidum was detected only in the extracellular fraction and increased five fold when induced by safflower oil in a shake culture (0.16 µM/min/mL supernatant at 24 h). Lipase expression was delayed in static cultures. Y. lipolytica showed lipase activity in extracellular, washed-cell and intracellular fractions under all conditions. Static cultures in both glucose and safflower oil media showed higher lipase activity than shake cultures. The lipase activity of Y. lipolytica was higher in the late stationary phase than in the log phase under all conditions tested. The highest lipase activity was detected in a 192 h static culture grown in safflower oil medium (0.13 µM/min/mg dry cell weight, 0.3 µM/min/mg dry cell weight and 4.29 µM/min/mL supernatant in the intracellular, washed-cell and extracellular fractions respectively). C. kefyr did not show any lipase activity (< 0.03 µM/min/mL culture) under any of the growth conditions tested. Proteinase activity was detected in the intracellular fraction of 72 h shake cultures of G. candidum grown in both glucose medium and safflower oil medium (154 and 122 RFU/min/mg dry cell weight respectively) but was not detected in static cultures. Proteinase activity was absent in the Y. lipolytica cultures under all conditions tested (< 10 RFU/min/mL culture). C kefyr showed low proteinase activity (12-74 RFU/min/mL supernatant) in the extracellular fraction only in shake cultures grown in glucose medium. Volatile compounds of the headspace were sampled and analysed using solid phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS). The concentrations of volatile compounds were highest in shake cultures grown in glucose medium for all three yeasts. All yeasts produced several alcohols. Several esters were also detected in the G. candidum and C. kefyr cultures whereas aldehydes were detected only in the G. candidum cultures. G. candidum and Y. lipolytica were selected for cheese production trials because of their active cheese ripening enzymes. These yeasts, grown under different conditions, were added to Cheddar cheese (10 L vat). The yeast adjuncts influenced the cheese ripening by lipolysis [in terms of the production of free fatty acids (FFAs) analysed by gas chromatography-flame ionisation detector (GC-FID)] and the production of volatile compounds (SPME-GC-MS), whereas proteolysis (analysed by size-exclusion high performance liquid chromatography) by yeast enzymes was not obvious. The influence of Y. lipolytica as an anaerobic adjunct to cheese ripening was dependent on the growth conditions used during its propagation in laboratory media. The concentration of total FFAs was very high (37.1 mg/g cheese at 6 months) when a 192 h Y. lipolytica culture grown in safflower oil medium was added to a cheese make, whereas the cultures grown in glucose medium did not have any detectable effect. Addition of G. candidum culture to the cheese curd was more effective than its addition to the cheese milk. Both G. candidum and Y. lipolytica lipase(s) selectively hydrolysed the long-chain unsaturated fatty acids from the milk triglyceride in the cheese environment. Also, Y. lipolytica lipase exhibited some selectivity towards hydrolysis of butyric acid from the milk fat in the cheese. 2-Heptanone, 3-methyl-2-butanone and 2-nonanone were detected (1-10 x 106 relative peak area) only in the cheeses with yeast adjuncts but not in the control cheese. Enhancement of the production of both conjugated linoleic acid (CLA) and ethyl esters in a washed-curd, dry-salted cheese (375 L vat), made with G. candidum, Y. lipolytica, Propionibacterium freudenreichii ssp. shermanii, Lactobacillus fermentum and Lb. rhamnosus, was only partially successful. Higher concentrations of ethyl esters (> five fold; analysed by SPME-GC-MS) were produced in the cheeses made with yeast adjuncts. However, the concentration of total CLA (free plus esterified; analysed by GC-FID) did not increase although a higher concentration of free linoleic acid (> 10 fold), the substrate for CLA synthesis, was produced in the cheeses made with yeast adjuncts. A study of the formation of aromatic volatile compounds by C. kefyr in a medium containing L-phenylalanine (L-phe) showed that the yeast's ability to produce phenyl ethanol, phenyl ethyl acetate and benzaldehydc (analysed by SPME-GC-MS) was enhanced with an increase in the initial L-phe concentration (in the experimental range; analysed by enzymatic assay using phenylalanine ammonia lyase), but the yield was very low (20-27%). The initial concentration of glucose (in the experimental range; analysed by enzymatic assay using Peridochrom glucose reagent) did not affect the production of these aromatic volatile compounds. This study successfully showed that the yeasts G. candidum and Y. lipolytica, when used as anaerobic adjuncts, can influence the ripening and flavour development in Cheddar and washed-curd, dry-salted cheeses. The study also showed the capability of C. kefyr to produce aromatic volatile compounds from amino acid fermentation but the yields need to be increased by further manipulation of the medium components and the culture conditions before this capability can be used commercially.

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Jahns, Anika Carolin. "Towards a better understanding of the polyhydroxyalkanoate synthase from Ralstonia eutropha : protein engineering and molecular biometrics : a thesis presented to Massey University in partial fulfilment of the requirement for the degree of Doctor of Philosophy in Microbiology." 2009. http://hdl.handle.net/10179/1081.

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Polyhydroxyalkanoates (PHAs) are polyesters composed of (R)-3-hydroxy-fatty acids. A variety of gram-positive as well as gram-negative bacteria and some archaea are able to produce these biopolymers as energy and carbon storage materials. In times of unbalanced growth, when carbon is available in excess but other nutrients are limited, PHA inclusions are formed. These granules are water-insoluble, stored intracellularly and can be maintained outside the cell as beads. The key enzyme for the formation of PHA inclusions is the PHA synthase PhaC, which catalyses the polymerization of (R)- 3-hydroxyacyl-CoA to PHA with the concomitant release of CoA. The PHA synthase from Ralstonia eutropha (currently Cupriavidus necator), which is covalently bound to the PHA granule surface, tolerates fusions to its N terminus without loss of activity. In this study it was investigated if it would also tolerate translational fusions to its C terminus. A specially designed linker was employed, aiming at maintaining the hydrophobic surroundings of the R. eutropha synthase C terminus to allow proper folding and activity. Two reporter proteins were tested as fusion partners, the maltose binding protein MalE and the green fluorescent protein GFP. As GFP is a hydrophobic protein itself, no additional linker between the PHA synthase and the reporter protein was necessary to produce PHA granules displaying the functional fusion protein on the surface. Principally, the PHA synthase PhaC tolerates translational fusions to its C terminus but the nature of the fusion partner influences the functionality. Recently, PHA granules have often been acknowledged as bio-beads. A one-step production allows the formation of functionalised beads without the need for further cross-linking to impart desired surface properties. PHA beads displaying a gold- or silica-binding peptide at the N terminus of PhaC were constructed and tested for their applicability. Additionally, these beads were able to bind IgG due to the ZZ domain of the IgG binding protein A, which was employed as a linker sequence. These functionalised beads can be used as molecular tools in bioimaging and biomedicine, combining organic core with inorganic-binding shell structures. In a different biomimetic approach, the display of ten lysine residues at the granule surface was achieved using the phasin protein PhaP as the anchoring matrix. Extensive work was performed in an attempt to also employ the synthase protein, but was unsuccessful. These positively charged bio-beads can be used for dispersion or crosslinking experiments as well as silica binding.

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Vaino, Federica. "Development of an energy monitoring and targeting methodology for the most efficient operation of chilled water systems : a thesis presented in partial fulfilment of the requirements for the degree of Master of Engineering in Energy Management at Massey University, Palmerston North, New Zealand." 2008. http://hdl.handle.net/10179/1420.

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The increasing price of oil and the destabilisation of the world’s climate are urging governments, businesses and individuals to constantly investigate energy-efficient technologies and methodologies and pursue the adoption of energy efficiency programmes in a global effort to reduce energy consumption, greenhouse gas emissions and ultimately energy costs. In New Zealand, one of the biggest industrial energy efficiency projects was started in 2002 by a multinational dairy company, the Fonterra Co-operative Group, in partnership with the energy service company Demand Response Ltd; the project currently aims at reducing by 15% the energy costs at all Fonterra’s major production sites throughout the country. This thesis, undertaken as part of the above project, examines the development and implementation of a structured and integrated energy monitoring and targeting methodology (M&T) for the most efficient operation of all Fonterra’s chilled water systems, with an initial focus on the ones installed at Clandeboye, one of the Fonterra’s sites involved in the energy saving project. A data collection system (Insite) was already in place at Clandeboye to enable storage and analysis of some of the site’s utility metering data. After identification of key chilled water system components and definition of data requirements for M&T purposes, an analysis of past energy consumption trends (based on multiple regression calculations) was carried out to develop an historical benchmark of the energy used, compare it with current energy performance and thus identify opportunities for future improvements. The creation of an M&T reporting system for presenting findings to operators and management was the last essential part of the thesis development. The study has highlighted that the robustness of the proposed regression model was badly affected by the unreliability of the existing data collection system and the uncertainty associated with poorly documented changes to operating conditions/plant configuration that had occurred over time. The conclusion is that, while the developed M&T methodology is theoretically valid and readily applicable, further developments are necessary (and recommended) to make it suitable for other similar systems.

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40

Dykes, Stuart. "The Effect of Dosage Rate on The Chemical and Sensory Changes Occurring During Micro-oxygenation of New Zealand Red Wine." 2008. http://hdl.handle.net/2292/2578.

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The technique of micro-oxygenation involves the deliberate addition of continuous, metered amounts of oxygen into a vessel of bulk wine during the maturation period (between the end of fermentation and bottling). The aim of the process is to improve the sensory properties of red wine, particularly the mouthfeel characteristics associated with the various polyphenol constituents. The success of the process appears to depend strongly on the ability to control the rate of oxygen dosage. The effect of dosage rate on the chemical and corresponding sensory changes of a red wine is the central theme of this thesis. A method of dosing oxygen (at typical micro-oxygenation rates) into small volumes of wine (<100 litres) was developed using a dense polymer membrane diffuser. It was clearly demonstrated that wine could be reliably oxygenated at very low rates using a coiled length of FEP as the diffuser material. Oxygen dosage was regulated by adjusting the oxygen pressure inside the tube. The advantage with a dense polymer diffuser is that no bubbles are generated and the oxygenation efficiency is 100%. The diffuser was fully modeled and characterised for use in the laboratory scale trials detailed in Chapters Four and Six. The small scale oxygenation equipment was used to conduct a fully replicated experiment to investigate the evolution of a Cabernet Sauvignon wine under four oxygenation treatments at dosage rates of 0, 10, 23 and 36 mg/L/mth. The total period of the trial was 105 days. HPLC analysis indicated that the rate change of low molecular weight polyphenols is directly related to the oxygen dosage rate. The concentration of the majority of the identifiable monomers, most notably the anthocyanins decreased throughout the course of the trial. The rate of decrease was directly related to oxygen dosage rate. Thiolysis results showed an increase in mDP for all treatments over the course of the trial until day 77 when they were observed to decrease for all treatments. The decrease in mDP coincided with an addition of SO2 which was investigated in a subsequent trial. Spectrophotometric results indicated that the rate of formation of non-bleachable pigments was directly related to the rate of oxygen dosage with significant differences between the high rates (23 and 36 mg/L/mth) and the low rates (0 and 10 mg/L/mth). The trend for all treatments was for increased levels of stable pigments. The sensory results show that the measured organoleptic temporal development exhibits a similar oscillatory behaviour compared to the anecdotally derived curve presented in figure 1-2. The distinction between the respective phases described in section 1.1.1 was, however less clear. The most significant factor in the model weighting was mouthfeel and astringency which correlates with the observed changes occurring in the wine polypenols during maturation. Overall the laboratory scale trial showed that the chemical polyphenol development was directly related to the oxygen dosage rate. The sensory evolution also appeared to be accelerated with higher oxygen dosage rates, although the oscillatory nature of the sensory response given a single linear input indicates a complex underlying mechanism driving the changes. The effect of SO2 on the development of wine polyphenols with and without oxygen was also investigated. The presence of SO2 was found to have a significant effect on both mDP and the concentration of non-bleachable pigments. mDP was observed to decrease over the six week trial period irrespective of whether oxygen had been added or not. The mDP for the treatments without SO2 increased steadily over the course of the trial. Similarly the formation of non-bleachable pigments was suppressed and even retarded with SO2 present whereas for the treatments without SO2 a steady increase was observed. The implication of these results is that SO2 may have a much larger effect on tannin development than oxygen. The use of electrochemical micro-oxidation (or ELMOX) was examined ostensibly to determine proof of concept and also compare the performance of glassy carbon and titanium as electrode materials against traditional micro-oxygenation. Notable transformations occurred with titanium showing higher levels of ethanal than the other treatments both chemically and by sensory measure. A greater rate of stable pigment formation was also observed for the titanium compared to the other treatments. The respective dosage rates for the glassy carbon ELMOX and traditional micro-oxygenation treatments were too low to be able to discriminate any significant differences compared to the control wine.
AGMARDT Doctoral Scholarship

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Wimalaratne, Sajith Kanchana. "Pressure assisted thermal sterilization: a novel means of processing foods." 2009. http://hdl.handle.net/2292/5294.

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This thesis investigates a newly developed and patented technology for its ability to inactivate spore- forming bacteria and non-spore-forming microorganisms. This new technology “Pressure Assisted Thermal Sterilization©” (PATS) is based on the theory of the thermal expansion of liquids. The efficiency of inactivating spore-forming and non-spore-forming microorganisms by PATS was compared with the thermal treatment alone. A combination treatment consisting of high pressure processing and gaseous carbon dioxide was also investigated for its ability to inactivate bacterial spores in model and real food matrices. The structural damage caused by treatments to the spores and non-spore-forming bacteria was assessed by scanning electron microscopy. Geobacillus stearothermophilus spores suspended in Milli-Q water, UHT milk and pumpkin soup, treated by PATS were found to have significantly lower decimal reduction times (D values) compared with the thermal treatment alone. Spores suspended in UHT milk were more heat resistant compared with those in Milli-Q water and pumpkin soup. Bacillus cereus spores suspended in Milli-Q water and pumpkin soup treated with PATS were more effectively inactivated compared with spores treated by the thermal treatment alone. Clostridium botulinum spores in saline buffer subjected to PATS treatment were inactivated more effectively compared with the thermal treatment alone. Overall, the results show that PATS was a better processing technique for inactivation of bacterial spores compared with thermal treatment alone. However, PATS had no added benefit in inactivating the non-spore-forming bacteria Escherichia coli and Saccharomyces cerevisiae cells compared with the thermal treatment. A shelf life study showed that B. cereus spores in pumpkin soup retained a low spore count (<5 LogCFU/mL) for approximately 40 days in 30oC storage after treatment with PATS. No additional degradation of colour pigments of pumpkin soup and model pumpkin juice was observed following PATS compared with the thermal treatment. Spore-forming microorganisms can be resistant to pressure treatment alone, which limits the application of high pressure processing (HPP). Therefore, a combination approach was investigated. The mechanism of inactivating spores by combining HPP with other treatments is that the pressure assists in spore germination. Then a secondary treatment (thermal or CO2 gas) can be used to inactivate the germinated spores. A combined application of HPP and a consecutive CO2 treatment was investigated for the efficiency of spore inactivation. Results showed that HPP (200 MPa for 30 min) followed by a CO2 treatment inactivated Bacillus subtilis 168 in nutrient broth, tomato juice and liquid whole egg by 2.5, 1.0 and 1.5 LogCFU/mL respectively. These results indicated that this technique is inadequate for practical use. Scanning electron micrographs showed that pressure processing of B. subtilis 168 and B. subtilis natto spores resulted in deformation of the spore structure. This structural deformation of spores may have been due to water absorption during HPP and subsequent release upon decompression. PATS treated G. stearothermophilus and B. cereus spores were more severely damaged compared with the same spores which underwent thermal treatment alone. However, the extent to which E. coli and S. cerevisiae cells were damaged by both PATS and thermal treatment was similar.

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Dissertations / Theses on the topic 'Fields of Research – 290000 Engineering and Technology – 290100 Industrial Biotechnology and Food Sciences'

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