Tesi sul tema "Dairy products"

The purpose of this study was to develop a short, easy procedure to measure five major proteins in milk and to detect concentrations of added protein to dairy products. Combinations of casein or whey protein with nonfat-dry milk were made with concentration ratios from 0:10 to 10:0. Similar mixtures of defatted goat milk with defatted cow milk were prepared. Samples were hydrolyzed in 6 N HCl at 145°C for 4 h and analyzed for amino acid composition. Multiple regression equations were derived to estimate the relative content of whey protein or casein added to nonfat-dry milk and goat milk added to cow milk employing amino acid profiles of whey protein, casein, nonfat-dry milk, goat milk and cow milk. Correlation coefficient values were all greater than .99. Measuring individual concentrations of milk proteins required separating casein and why proteins by reverse phase high performance liquid chromatography on a C3 column. αs-, β-, and κ-casein were separated after dissociating casein micelles with mercaptoethanol and urea. A 40:60 to 0:100 gradient of .15 M sodium chloride/triethylamine (pH 2.5) and 40% acetonitrile was used. Whey proteins, α-lactalbumin and β-lactoglobulin were separated with a 95:5 to 0:100 gradient of .15 M sodium chloride (pH 2.4) and acetonitrile. Eluted proteins were collected from the column, analyzed for purity by electrophoresis, and hydrolyzed in 6 N HCl at 145°C for 4 h. Purified proteins and mixtures of purified proteins were analyzed for amino acid composition. Estimates of individual protein concentrations in mixtures were made by solving simultaneous equations based on amino acid composition using a tektronix 4052 computer.

L’utilizzo di tecnologie non termiche per la conservazione degli alimenti (campi elettrici pulsati, luce pulsata, luce UV, irradiazione, ultrasuoni) potrebbe rappresentare una strategia alternativa per aumentare la stabilità dei prodotti freschi. Differenti studi sono stati riportati sull’utilizzo di queste tecnologie su vari alimenti (frutta, verdura, carne cruda e pesce, succhi di frutta e latte), ma pochissime informazioni sul Fiordilatte sono disponibili. Sulla base di queste considerazioni, potrebbe essere interessante valutare l'efficacia di queste tecnologie non termiche sul Fiordilatte, al fine di prolungare la sua shelf-life. In questa tesi di dottorato è stato studiato il potenziale utilizzo di tecnologie non termiche per la sanificazione di formaggi freschi. In particolare, sono stati testati sul Fiordilatte l'efficacia di diversi trattamenti: la luce UV-C, la luce pulsata (PL), gli impulsi di luce ad alta intensità (HILP), un sistema costituito da ultrasuoni combinati con il vapore (SonoSteam), i raggi X e il plasma freddo mediante l’utilizzo di un sistema Plasma jet. Per ogni strategia di conservazione, sono stati effettuati test preliminari in vitro utilizzando Pseudomonas fluorescens, (o un mix costituito da P. fluorescens e P. putida) e Enterobatteriaceae come inoculo sulla superficie del Fiordilatte. Poi, nella prova di shelf-life i campioni non trattati e trattati sono stati confezionati con liquido di governo, conservati a 9±1 °C e periodicamente analizzati dal punto di vista della qualità microbiologica e sensoriale. I trattamenti con luce UV-C sono stati eseguiti in una cella termostatata dotato di 4 lampade UV-C, che emettono luce nella lunghezza d'onda tra 180-200 nm. I trattamenti con luce pulsata (PL) e impulsi di luce ad alta intensità (HILP) sono stati eseguiti utilizzando rispettivamente una unità di decontaminazione mobile (CLARANOR) e Steri-Pulse XL 3000. Questi dispositivi sono dotati di lampade allo xeno, che emettono luce ad alta intensità nella lunghezza d'onda tra 100-1100 nm. I trattamenti con ultrasuoni combinati con il vapore sono stati eseguiti con un impianto pilota dotato di 6 ugelli, in grado di produrre in maniera simultanea vapore (90-95 °C) e ultrasuoni (20-40 kHz). Il trattamento a raggi X è stato eseguito con il dispositivo RS-2400 (Rad Source, USA) utilizzando tre diverse dosi (0.5, 2, 3 kGy). Mentre, il trattamento con plasma jet è stato effettuata utilizzando un sistema pilota dove il getto di plasma è montato in una piccola camera che permette di lavorare a pressione atmosferica. L’Elio o una miscela di Elio + Ossigeno sono stati utilizzati come gas per la formazione del plasma. Per ogni strategia di conservazione, la crescita delle Enterobatteriaceae e delle Pseudomonas spp. è stata presa in considerazione, essendo questi gruppi microbici i responsabili principali del deterioramento dei prodotti lattiero caseari. Dalle prove preliminari con i campioni inoculati, la luce UV-C è stata in grado di decontaminare la superficie del Fiordilatte. È stata ottenuta un'estensione della shelf-life del 80% selezionando adeguate modalità di trattamento come l'esposizione del Fiordilatte ai raggi UV-C a 6.0 kJ/m2. Il trattamento con la luce pulsata (PL) ha permesso una riduzione della crescita microbica, soprattutto immediatamente dopo il trattamento ed è stato osservato che la carica microbica diminuisce con l'aumentare della intensità della luce. Durante il test di shelf-life i risultati confermano che il trattamento PL esercita una attività germicida iniziale, ma non è in grado di inibire la crescita microbica durante la conservazione. Mentre, per il trattamento con impulsi di luce ad alta intensità (HILP) è stato osservato una riduzioni significativa (oltre 1 ciclo log) su Fiordilatte inoculato, con solo pochi secondi di trattamento (da 1 a 8 s). Durante il periodo di stoccaggio refrigerato, nei campioni controllo si è osservato un aumento delle Pseudomonas spp., mentre i campioni trattati(per 2 e 4 s) non hanno mai raggiunto il limite di accettabilità microbiologica (dopo 12 giorni di stoccaggio). Nello studio effettuato con ultrasuoni combinati con il vapore tutti i dati del test in vitro hanno evidenziato che questa tecnica può essere particolarmente efficace per ridurre la contaminazione iniziale del Fiordilatte. Durante il periodo di stoccaggio per le Pseudomonas spp., i campioni trattati (per 1 s e 6 s) non hanno mai raggiunto la soglia di accettabilità microbiologica (dopo 12 giorni di stoccaggio). Pseudomonas spp. e Enterobatteriaceae, non sono stati rilevati nei campioni irradiati (trattamento a raggi X), indicando che questi gruppi microbici alteranti sono stati completamente inibiti dal trattamento a raggi X, mentre sono cresciuti nel controllo. La shelf-life per i campioni trattati con 2 e 3 kGy è stata circa di 44 e 43 giorni, rispettivamente. Mentre il controllo è rimasto accettabile per circa 10 giorni. Al contrario, i tempi di trattamento lunghi, la modalità di applicazione del plasma e l'inefficacia sono stati i problemi connessi al potenziale utilizzo del plasma jet. Pertanto, le indagini con questa tecnologia sono state interrotte. In generale, per i parametri sensoriali il punteggio della qualità globale ha indicato un accettabilità dei campioni di Fiordilatte trattati (UV-C, PL, X-ray) e questi sono stati percepiti come paragonabile ai campioni di Fiordilatte non trattati (controlli). L'efficacia di queste tecnologie è molto interessante, in quanto riduzioni microbiche significative sono state registrate nella maggior parte dei campioni trattati. L'applicazione di queste nuove tecnologie a livello industriale ha ancora bisogno di altre indagini per meglio valutare gli effetti su alcuni parametri nutrizionali e costi per lo scale-up.

Thesis (M.A. in economics)--Washington State University, August 2009.
Title from PDF title page (viewed on Sept. 15, 2009). "School of Economic Sciences." Includes bibliographical references (p. 18-20).

Background: Type 2 diabetes mellitus is one of the most prevalent chronic diseases worldwide, currently affecting about 3 million global populations. The incidence of Type 2 diabetes has been increasing particularly in recently developed Asian settings including Hong Kong. Dairy product, as a part of dietary guidelines, has been hypothesized to help reduce risks of Type 2 diabetes. However different types of dairy product might have different effects on Type 2 diabetes given their varying content in fat, sugar and vitamins. Objective: To review literature on the examination of the association between consumption of different types of dairy products (total dairy, high-fat dairy, low-fat dairy and fermented dairy) and the risk of type 2 diabetes Methods Relevant studies were searched and identified through database of PubMed and Google Scholar using combination of keywords. Studies examining the association between consumption of total dairy and subtypes of dairy products and the risk of type 2 diabetes were included. Results: Of the 163 papers identified, 10 studies were finally included in this systematic review. All studies were prospective cohort study from Western countries. Findings for different kinds of dairy products varied. For high-fat dairy products consumption, nine out of the ten studies found there was no association with type 2 diabetes risks. For low-fat dairy products, six out of ten studies found an inverse association after adjusted for confounders like age, sex and total energy intake; among these six studies, three still reported an inverse association after further adjusted for confounders like education level, smoking status and alcohol intake, physical activities and family history of type 2 diabetes. For fermented dairy products (mainly yoghurt), among seven studies which examined this, three studies found an inverse association between yogurt consumption and Type 2 diabetes risk before and after adjusted for multivariate confounders (age ,sex, total energy drink, education level, social class, physical activities, smoking status, alcohol intake and family history of type 2 diabetes, etc) . One of the three studies also found that, other than yogurt, there was an inverse association between low-fat fermented dairy and total fermented dairy consumption and type 2 diabetes risks after adjusted for age and sex. However, after further adjustment, the association became null for total fermented dairy products while it remained for low-fat fermented dairy products. All of the 10 studies that examined subtypes of dairy product also reported total dairy product consumption. For total dairy product, six out of ten studies found an inverse association. Conclusion: Overall, total dairy consumption might be associated with lower risks of type 2 diabetes, but the associations may be varied by subtypes of dairy products. Across different types of dairy products, low-fat dairy consumption was associated with lower risk of type 2 diabetes while high-fat dairy consumption was clearly not associated with type 2 diabetes risk. Results for subtypes of fermented dairy consumption remain unclear. Further prospective cohort study in other non-Western populations may provide are required.
published_or_final_version
Public Health
Master
Master of Public Health

Menaquinones (MK’s) are a form of vitamin K, supplementation with which has been shown to provide health benefits by reducing arterial calcification and improving bone density. Fortifying MK’s in foods may provide the health benefits associated with MK’s to the general population. This study aimed to increase the amount of MK’s in yogurt, which typically contains very little MK’s, by co-fermenting milk with both typical yogurt bacteria and bacteria known to produce MK’s in cheese and natto. A LC-MS/MS method was first developed to measure MK’s as well as all other fat-soluble vitamins. The LC-MS/MS method was able to quantify phylloquinone, MK-4, MK-7, MK-9, cholecalciferol, α-tocopherol, and was able to detect MK-8, but was unable to quantify ergocalciferol or retinol due to ionization suppression from the sample matrix. The LC-MS/MS method was used to measure MK’s in non-fat milk samples fermented with either one bacteria ssp. or a combination of S. thermophilus, L. bulgaricus, and one of L. lactis, L. cremoris, P. shermanii, or B. subtilis. Fermentations were carried out at 30 – 45 °C for 36 h to determine the optimal incubation temperature at which to carry out replicate fermentations. The pH was measured throughout fermentation as an indicator of overall growth and the relative amount of each bacteria ssp. after fermentation was measured using qPCR. Only L. cremoris produced MK-8 and MK-9, while all samples, including negative controls, contained high concentrations of MK-7. The qPCR results showed co-fermentations contained over 99 % S. thermophilus, except in co-fermentations with L. lactis which contained 59 % L. lactis, 41 % S. thermophilus, and < 0.1 % L. bulgaricus. Delaying inoculation of S. thermophilus and L. bulgaricus resulted in almost exclusive growth of the first inoculant. Overall, L. cremoris showed the greatest potential for enhancing the MK content of yogurt as it produced up to 234.4 ng/g MK-9, 174.9 ng/g MK-7, and produced MK-8, but further experiments are required to improve the growth of yogurt and MK producing bacteria.
Land and Food Systems, Faculty of
Graduate

The aim of the study in this thesis was to assess the stability of the mycotoxin, cyclopiazonic acid (CPA) in milk and dairy products processed from contaminated milk. A method was developed to detect CPA in milk and milk products using micellar electrokinetic capillary chromatography (MEKC), a technique of capillary electrophoresis (CE), which was rapid and non-labour-intensive. The quantifying efficiency of CE in detecting CPA was compared to Reverse Phase Liquid Chromatography. Heat-stability of CPA in milk was assessed under different conditions. A longer heat treatment of 60 degrees centigrade for 30 minutes led to a 10% decrease in the level of CPA. The results from this thesis demonstrate that CPA in milk at concentrations found in naturally contaminated milk could not be eliminated by the heat-treatment during milk processing, storage, processing and manufacture of dairy products. Occurrence of CPA in cheese curd, butter or cream following manufacture with contaminated milk was demonstrated. CPA is left in milk despite UV-visible radiation treatment with or without hydrogen peroxide and/or riboflavin. Chemical treatment, which is capable of completely eliminating CPA, is prohibited and impractical to use for milk treatment. Stability of CPA in milk and milk products confirms the potential of the toxin to reach consumers of dairy products.
Doctor of Philosophy (PhD)

The objective of this thesis is to advance our understanding of how consumers use date labels and the implications of date-label use for household dairy product waste. It does this by investigating the effect of psychological, social, and contextual factors on date-label use and willingness to consume dairy products in relation to the expiry date. These effects are tested using structural equation models and survey data gathered from 548 Scottish consumers. The results of this study make two contributions to the literature on date-labelling and food waste. The first contribution is primarily theoretical. By improving our understanding of how consumers use date labels and the implications of date-label use for household dairy product waste, it supports the contention that food waste is best understood, not as a behaviour, but as the outcome of multiple behaviours. It argues that in order to understand why food waste is created, it is important to identify the factors that affect the individual behaviours that lead to it, such as date-label use, and how these behaviours relate to one another. These results also have implications for communications and campaigning around food waste reduction. The second contribution has policy relevance. It provides evidence of the likely limited effect of increasing the number of dairy products labelled with a best-before date rather than a use-by date on food waste. This is an approach recently proposed to reduce household food waste. It finds that better knowledge of the best-before date is associated with a higher willingness to consume products after the best-before date has passed. However, perceived risks about consuming products beyond their best-before date, including not just safety but quality, freshness, and social acceptability, appear to interact with date-label knowledge and dampen its influence. It argues that to be effective, any changes in date-labelling should be accompanied by communication that goes beyond improving date-label knowledge, and addresses the multifaceted nature of related risk perceptions and conceptions of date-label trust.

The aim of the study in this thesis was to assess the stability of the mycotoxin, cyclopiazonic acid (CPA) in milk and dairy products processed from contaminated milk. A method was developed to detect CPA in milk and milk products using micellar electrokinetic capillary chromatography (MEKC), a technique of capillary electrophoresis (CE), which was rapid and non-labour-intensive. The quantifying efficiency of CE in detecting CPA was compared to Reverse Phase Liquid Chromatography. Heat-stability of CPA in milk was assessed under different conditions. A longer heat treatment of 60 degrees centigrade for 30 minutes led to a 10% decrease in the level of CPA. The results from this thesis demonstrate that CPA in milk at concentrations found in naturally contaminated milk could not be eliminated by the heat-treatment during milk processing, storage, processing and manufacture of dairy products. Occurrence of CPA in cheese curd, butter or cream following manufacture with contaminated milk was demonstrated. CPA is left in milk despite UV-visible radiation treatment with or without hydrogen peroxide and/or riboflavin. Chemical treatment, which is capable of completely eliminating CPA, is prohibited and impractical to use for milk treatment. Stability of CPA in milk and milk products confirms the potential of the toxin to reach consumers of dairy products.

Thesis (Ph.D.) -- University of Western Sydney, Hawkesbury, 1998.
"A thesis presented to the University of Western Sydney for the degree of Doctor of Philosophy, September, 1998" Bibliography: leaves 193 - 219.

Thesis (M.S.)--West Virginia University, 2006.
Title from document title page. Document formatted into pages; contains ix, 106 p. Vita. Includes abstract. Includes bibliographical references (p. 77-81).

Canadian dairy market has been highly protected by the Federal Government for several decades. The current situation is the over-quota tariffs of dairy products are extremely high. However, it is possible to anticipate that this high over-quota tariff will be reduced in the future WTO negotiations. This paper tries to answer by how much tariff can be cut and still maintain protection from imports for the domestic dairy industry. This is also equivalent to test how much water in the tariff (WIT) for dairy products. The time series dairy products wholesale prices data of Canada and the world are used in the calculations. The methodologies are introduced in this paper to estimate WIT for four dairy products including butter, skim milk powder, cheddar and fluid milk (2% fat). In addition, I define the potential WIT and measure that by using adjusted Canadian wholesale price (equaling US dairy processor’s market margin plus Canadian farm milk cost). In addition, how much WIT and potential WIT in the coming decade (2008-2017) are forecasted according to the predicted prices. The results show that there are large amounts of water in the Canadian over-quota tariffs in the period of 1996-2017, they vary across dairy products and over time. Finally, the policy recommendations have been made on the question of how much percent of the over-quota tariff can be reduced without increasing imports in the coming decade when the international prices are stochastic but their development trends are certain.

Milk and dairy products are important source of bioactive compounds useful to satisfy the nutritional and physiological needs of any newborns of mammalian species and useful to guarantee adequate growth and development of infants as well as provide a complete nourishment of adults. Physico-chemical, nutritional and organoleptic properties of the main constituents and the “minor” components have a crucial role in the quality of milk and milk products. Although in the past decades dietary milk fat was often regarded as harmful for the human health, recent researches suggest that milk contains specific fatty acids with nutritional and physiological health benefits. For these reasons, a major attention is given to the quantity and quality of total fat intake. In the recent years, as a result of the new concept of multifunctional agriculture and the changing behaviours about diet, consumer demands in favor of high-quality, security and safety dairy products are increased. Moreover, milk proteins and milk-derived bioactive peptides are recognized to have a high nutritive value, several health-promoting functional activities and excellent technological properties. Accordingly, growing interest in the development of functional dairy products and preparation of infant formulae for babies who cannot be breast-fed, has been give in order to meet the specific consumer’s requests. This manuscript presents the main results obtained during my PhD research aimed to evaluate the main bioactive lipids and proteins in milk and dairy products using innovative analytical techniques. The experimental section of this manuscript is divided in two sections where are reported the main results obtained during my research activities on dairy products and human milks in order to characterize their bioactive compounds for functional food applications.

Milk and dairy products are important source of bioactive compounds useful to satisfy the nutritional and physiological needs of any newborns of mammalian species and useful to guarantee adequate growth and development of infants as well as provide a complete nourishment of adults. Physico-chemical, nutritional and organoleptic properties of the main constituents and the “minor” components have a crucial role in the quality of milk and milk products. Although in the past decades dietary milk fat was often regarded as harmful for the human health, recent researches suggest that milk contains specific fatty acids with nutritional and physiological health benefits. For these reasons, a major attention is given to the quantity and quality of total fat intake. In the recent years, as a result of the new concept of multifunctional agriculture and the changing behaviours about diet, consumer demands in favor of high-quality, security and safety dairy products are increased. Moreover, milk proteins and milk-derived bioactive peptides are recognized to have a high nutritive value, several health-promoting functional activities and excellent technological properties. Accordingly, growing interest in the development of functional dairy products and preparation of infant formulae for babies who cannot be breast-fed, has been give in order to meet the specific consumer’s requests. This manuscript presents the main results obtained during my PhD research aimed to evaluate the main bioactive lipids and proteins in milk and dairy products using innovative analytical techniques. The experimental section of this manuscript is divided in two sections where are reported the main results obtained during my research activities on dairy products and human milks in order to characterize their bioactive compounds for functional food applications.

To reduce food safety risks and prevent serious food safety incidents, and enhance consumer confidence in food safety, the Chinese government has undertaken various policy measures to improve the safety and quality of dairy products in recent years. The implementation of traceability systems could lead consumers to perceive a higher value and to be willing to pay a premium price for dairy products. This research contributes valuable information to the dairy product supply chain, providing insights to producers, distributors, and other actors of the dairy production chain. Results showed that the importance of information about food traceability for improving market demand for traceable dairy products. Further work will be needed to improve consumers' understanding of the potential benefits of traceable systems in the dairy product quality and security system. Moreover, encouraging producers to produce diversified traceable dairy products, decrease the production cost, decreasing the price of traceable dairy products may be the most effective way of increasing the traceable dairy food market share.

Six odor-reducing commercial products were tested for their efficacy in reducing odors from dairy and swine wastes. A sensory panel method was utilized for odor evaluations, in which the panel played an important part. Comparisons between products were made for agitated and unagitated conditions and effect of storage time (three weeks in which experiments were performed). Cotton pieces tied to the mouth of the sample jars were useful in absorbing the odors. Odor-treated jars were observed and evaluated by panel members. The odors were rated on a discrete scale of 0-5, with '0' being no odor and '5' the highest odor level of dairy or swine waste. The products were analyzed for their effectiveness on dairy and swine wastes separately. The "General Linear Model" was used for data analyses, and all the products were compared for their effectiveness under each waste storage condition and elapsed storage time. Each product was able to reduce odors. For both dairy and swine wastes, one product stood out and was very effective, whereas another product was less successful. Unagitated storage conditions of swine waste favored the product performance. Unagitated storage conditions were also found to be better for most of the products; only two products were slightly better in effectiveness under agitated storage conditions. The effect of storage time on product-effectiveness for each product for both dairy and swine waste varied. Odor levels from unagitated swine waste was very low in the beginning, but became worse with increasing storage time. Dairy waste in unagitated conditions had slightly higher levels of odors in the beginning, but became a little less with increasing storage time. Under the conditions of this study, it can be recommended that: 1) P2 has a better chance in reducing odors, 2) in general, unagitated conditions favor the reduction in odor levels, and 3) dairy waste should be treated in the first few days following collection, whereas swine waste should be treated when it is old. Testing of these products in actual field conditions would provide stronger support for these findings.
Master of Science

The rapid expansion of China’s dairy herd in recent years, with a primary objective of increasing milk production, has given rise to speculation on the potential beef production from this Chinese black and white herd. This study examines whether or not economic incentives exist for dairy and beef producers in China to adopt dairy—beef production and the impact of dairy-beef production on Chinese beef supply, demand and international trade.

This thesis presents several Raman spectroscopic studies of bovine milk-derived products (skim and whole milk powder, anhydrous milk fat, processed cheese and soy cheese made from milk protein). Raman spectroscopy, unlike infrared spectroscopy (both mid- and near-infrared), has not been widely used as an analytical tool within the dairy industry. The purpose of this project was to assess the utility of Raman spectroscopy in several dairy industry relevant problems. FT-Raman spectroscopy coupled with partial least squares (PLS) reliably predicted the concentration of fat and protein within whole milk and protein within skim milk powders as evidenced by ratios of prediction to deviation in excess of three. It was shown that sample geometry did not significantly affect the calculated predictive models, thereby allowing the simplest, quickest method of sample presentation to be utilised without harming quantification model efficacy. The fat fraction of milk was further investigated, and it was shown that Raman spectra collected from anhydrous milk fat samples were a good basis for solid fat content (SFC) determination. Such spectra were collected when the samples were held at 40 �C, pretreated by baselining and area normalisation, and analysed using PLS with modified jack-knifing (PLS1-JK). Triacylglycerol class concentrations were also well predicted by PLS1-JK models developed from Raman spectroscopic data. Resonance enhancement of β-carotene within fat was shown to have little effect on the reliability of the optimal prediction model when compared to SFC Raman quantification. Raman microscopic mapping for heterogeneity description of processed cheese and soy cheese mimics was examined. The FT-Raman milk powder constituents study had shown fat and protein Raman spectra within complex dairy mixtures could be distinguished, hence this utility was applied to mapping of cheese systems. Univariate, principal components analysis and multivariate curve resolution methods of analyses were compared; as expected the more complex samples required multivariate methods of analyses. Raman microscopic mapping was not a time efficient method in comparison to the standard method of confocal laser scanning microscopy. However, Raman spectroscopic mapping is a more universal technique which allowed the presence of an unexpected localised constituent within the soy cheese mimics to be observed. It was proposed that this constituent was a crystalline form of a short saturated fatty acid.

Deux souches de Lactobacillus pentosus, Ind1 et Ind3, ont été isolées à partir de « Naigeda », un fromage traditionnel Chinois produit dans la région du Xinjiang. Les propriétés probiotiques de L. Pentosus étant peu connues, la présente étude a été conduite afin de déterminer si ces 2 souches, Ind1 et Ind3, sont susceptibles d’être utilisées comme probiotiques. Les propriétés physiologiques de L. Pentosus Ind1 et Ind3 ont fait l’objet d’essais in vitro afin de déterminer leur tolérance à l’environnement gastro-intestinal et leur adhérence à l’épithélium intestinal. Leurs propriétés de dégradation de 3 substances carcinogènes (phénol, p-crésol et indole ; concentrations comprises entre 50 et 150 µg/mL) ainsi que leur inhibition éventuelle par ces mêmes substances ont été étudiées. Les effets des 2 souches de L. Pentosus sur la microflore intestinale de souris, après administration orale de 109cfu/mL dans 0. 5mL de lait écrémé, ont été analysés. A cet effet, les populations de Lactobacilles, Bifidobactéries, Entérobacilles, Entérocoques et Clostridium perfringens, contenues dans les fèces des souris, avant, pendant et après leur alimentation en probiotiques, ont été considérées. Enfin, les capacités des 2 souches de L. Pentosus à produire de l’acide -amino butyrique ont été étudiées, et les conditions de milieu et de culture assurant la meilleure production définies. Les résultats montrent que les 2 souches de L. Pentosus, Ind1 et Ind3, présentent des taux de survie élevés : plus de 90 % en milieu acide et de 80% dans une solution de bile. Les aptitudes à l’adhérence sont souches dépendantes, avec pour Ind3 un potentiel similaire à celui de souches probiotiques reconnues (NCFM et Lp115). Ind1 et Ind3 ont également montré une bonne résistance aux substances carcinogènes (phénol, p-crésol, indole à 150 μg/mL). Enfin, ces 2 souches permettent un accroissement des concentrations de Lactobacilles et de bifidobactéries, dans le tractus intestinal des souris, tout en inhibant la croissance des Entérobacilles et de C. Perfringens. Ces résultats démontrent les aptitudes potentielles des deux souches de L. Pentosus étudiées pour une utilisation comme souches probiotiques au sein de régimes diététiques ou pour l’élaboration de produits laitiers fermentés
Two Lactobacillus pentosus strains, Ind1 and Ind3, were isolated from a traditional Chinese cheese product called Naigeda, collected from Xinjiang region of China. Since there is little information regarding the probiotic properties of L. Pentosus strains, this study was designed to provide more supporting data for L. Pentosus as a potential probiotic strain application. The physiological properties of the two L. Pentosus strains, Ind1 and Ind3, such as the in vitro test on the intolerance under the gastro-intestinal environment, the ability of adherence on the intestinal epithelium were studied. Their intolerance as well as inhibition and degradation ability under presence of pre-carcinogenic substances existing in human gut such as phenol, p-cresol and indole at different concentrations were also determined. The effects of the two L. Pentosus strains on modulation of the mice intestinal micro flora, by oral administration of 109cfu/ml of strains in 0. 5ml of skim milk, were investigated: the amounts of Lactobacillus spp. , Bifidobacterium spp. , Enterobacilli, Enterococcus and Clostridium perfringens in the feces of mice during and after the feeding of probiotic strains were counted. Furthermore, the technological properties of the two L. Pentosus strains on their GABA producing ability were studied: the medium and process parameters optimization was carried out in order to try to obtain the highest GABA content in the fermented dairy products. Results showed that the two L. Pentosus strains had high survival rates (higher than 90% in acid and 80% in bile solution). The adhesive ability is strain independent: Ind3 adherence was comparable with those of two commercial probiotic strains (NCFM and Lp115). Ind1 and Ind3 showed good resistance mutagenic substances phenol, p-cresol, indole at concentration below 150 μg/mL). Ind1 and Ind3 also showed certain effect on promoting the increase of Lactobacillus and Bifidobacteria counts, and inhibiting the growth of Enterobacilli and Clostridium in mice gut. These results displayed positive properties that the two L. Pentosus strains can be good candidates to be used as probiotic strains potentially used in dietary supplement application or Chinese-style dairy products

ABSTRACT Within the complex bacterial community of traditional raw milk cheeses, lactic acid bacteria (LAB), naturally present in the milk as adventitious contaminants, play the key role in the cheese manufacture and ripening process through their acidifying, proteolytic and flavouring activities. Moreover, LAB contribute considerably to the microbial safety, since they produce organic acids and bacteriocins that extend shelf-lives of raw milk products. Numerous LAB genera and species such as Lactobacillus, Lactococcus, Streptococcus, Leuconostoc and Enterococcus are involved in these metabolic activities. This natural microbial biodiversity can be considered a heritage which has to be protected and preserved, since alterations in the composition of the beneficial autochthonous microbiota is of critical importance in maintaining the peculiar features of the traditional raw milk products. On the contrary, LAB may have also negative traits, such as the ability to produce toxic biogenic amines, possession of transmittable antibiotic resistance genes, and the potential for expression of putative virulence factors. Dairy safety aspects should include careful examination of these harmful features. Therefore, the study of micro-organisms at species and strain level and the monitor of their dynamics in the microbial community throughout cheese manufacture and ripening is helpful to improve the quality and safety of the final product. Classical microbiological and molecular techniques have been widely used to investigate the dairy biodiversity and to achieve the characterization of bacterial species present in a complex microbial dairy ecosystem, highlighting the advantages and the limitations of both methods. The aims of PhD thesis were: I) to apply a polyphasic approach based on different phenotypic and molecular techniques for the characterization of the LAB isolated from dairy products collected throughout the technological process of an artisanal raw milk cheese, such as “Formagèla Valseriana”; II) to evaluate the application of total microbial DNA extracted directly from dairy products as template in PCR 16S-23S rRNA region spacer analysis (RSA-PCR) in order to achieve a rapid knowledge about their microbial communities, bypassing the previous step of isolation in pure culture; III) to investigate the influence of equipment (thermocycler) and reagents (Taq polymerase) on results obtained from RSA analysis; IV) to explore the functional and safety aspects of E. faecalis strains isolated from dairy products collected in different North Italy regions through the study of their biodiversity, bacteriocin, volatic organic compounds and biogenic amines production, virulence factors and antibiotic resistance. Firstly, evolution of bacterial groups during the cheese-making process of “Formagèla Valseriana” was revealed by viable counting of LAB and non-LAB micro-organisms. A total of 143 presumptive LAB strains from milk culture, curd and cheese samples were randomly selected from agar plates and subjected to morphological and phenotypic characterization (microscopic examination, Gram staining, catalase test, growth at 15 and 45 °C, CO2 production from glucose) and molecular identification. To investigate LAB biodiversity, the taxonomic position of the isolates was established through RSA-PCR combined with a species-specific PCR assay. Strains characterized by atypical classes of spacer were identified by partial 16S rRNA sequencing. Random amplified polymorphic DNA analysis (RAPD-PCR) was carried out to explore the genetic diversity of LAB isolates. In addition, this study was intended to evaluate the application of microbial DNA extracted directly from dairy products as template in RSA-PCR in order to achieve a rapid knowledge about their microbial communities, bypassing the previous step of isolation in pure culture. As expected in raw milk cheeses, LAB (i.e. lactobacilli, lactococci and enterococci) were quantitatively the dominant group for all samples. The combination of various molecular procedures allowed many species to be detected. In particular, milk culture showed a prevalence of Streptococcus thermophilus, whereas the most detected LAB in curd belonged to the species Lactococcus lactis ss lactis, Lc. garvieae and Enterococcus durans. E. durans was the species most frequently isolated from cheese samples, even if several species (E. faecalis, E. gilvus, E. italicus, Lb. paracasei ss paracasei, St. bovis, Lb. plantarum, Lb. coryniformis and Ln. mesenteroides), which are indicative of biological richness, were also present. RAPD-PCR revealed a high biodiversity at species level, but it also showed the presence of significant genetic variability among the isolates belonging to the same species. RSA, using as template DNA extracted directly from milk culture, did not prove to be a suitable method for discrimination of microbial species in a complex matrix, since when microbial community was very heterogeneous and rich, it was difficult discerning LAB species or genera. Actually, the band of S. thermophilus represents the only one that could be frequently identified. The 143 LAB strains were then screened for their inhibitory activity against Listeria monocytogenes and Staphylococcus aureus and for their acidifying activity. Seven and six strains, mainly belonging to the Enterococcus genus, exhibited antagonistic activity against L. monocytogenes and S. aureus, respectively. With regard to acidifying activity, the majority of isolates (88.8%) were found to be low acidifying isolates, causing a pH decrease lower than 1.5 pH units, whereas only 16 strains were classified as medium acidifying isolates and could be considered the fastest acidifying strains. Yet, after 24 h 74.1% of the isolates showed a medium acidifying ability and 9.1% were classified as high acidifying strains. As revealed by screening the microbial population of “Formagèla Valseriana”, the Enterococcus genus is one of the most prevalent within dairy microbial community. However, enterococci are ascribed the most controversial nature, presenting both beneficial and negative features. They represent important nosocomial pathogens, but are also recognized to produce bacteriocin with antibacterial activity and to enhance flavour and aroma development in cheese. For this reason, 40 Enterococcus faecalis strains isolated from raw milk products (milk, curd and cheese) collected throughout the technological process of various North-west Italian traditional cheeses (Aosta Valley, Piedmont and Lombardy) over a 13 year period (1997-2009) were examined. The genetic biodiversity of E. faecalis isolates was assessed through RAPD-PCR and repetitive extragenic palindromic PCR (rep-PCR). Phenotypic and molecular protocols were applied in order to investigate the incidence of antibiotic resistance and virulence factors among strains. They were examined for their antimicrobial activity against 18 foodborne spoilage and pathogenic bacteria. Investigation was also made to identify their bacteriocinogenic potential by searching for bacteriocin-encoding genes (enterocin A, enterocin B, bacteriocin 31, enterocin P, enterocin Q, enterocin L50A-B, mundticin KS, enterocin CRL35, enterocin AS-48, and enterocin 1071A-B). In addition, they were inoculated in milk and submitted to head-space solid-phase-micro- extraction gas chromatography-mass spectrometry analysis in order to study their capability for production of volatile organic compounds (VOCs). Resistance to streptomycin (50%), quinupristin-dalfopristin (32.5%), tetracycline (25%), rifampicin (7.5%), chloramphenicol (5%) and erythromycin (2.5%) were evidenced. Ampicillin, ciprofloxacin, levofloxacin, mupirocin, nitrofurantoin, penicillin G and vancomycin were revealed effective antimicrobials against all the strains considered. Tetracycline resistance was also confirmed by detection of tet(M), tet(K), tet(L), tet(S) and transmissibility of resistance by integrase gene (int) of the Tn916/Tn1545 family of transposons. The high incidence of tet(M) gene, found in 90% of the isolates, doesn’t correlate with their phenotypic expression, thus highlighting the presence of silent genes. The phenotypic assay of haemolytic activity showed positive results (β-haemolysis) only in 2 strains. Among the 7 virulence determinants tested, only gel, asa1, esp and efaA genes were harboured. None other gene encoding for either different virulence factors (cylA, hyl, ace), or amino-acid decarbolylase activity (hdc, tdc, odc) was detected. Our results suggest that dairy enterococci don’t represent the major potential reservoir for the spread of the investigated detrimental traits in contrast to other strains of different origin. Considering their antimicrobial activity, all the E. faecalis tested were active against at least 1 of the 18 indicator strains. Remarkable inhibitory effects against harmful or detrimental microbial species, including Bacillus cereus (44.7% of strains), Escherichia coli (17.5%), L. monocytogenes (15%), St. aureus (2.6%), and Clostridium sporogenes (21.1%), was detected. Moderate antagonism towards LAB (65.8% of strains), especially Lactobacillus delbrueckii subsp. bulgaricus and Lactobacillus helveticus, was found, too. However, 31.6% of E. faecalis strains were reported as ideal preservatives. Of the 10 enterocin structural genes explored, only gene for enterocin AS-48 was identified, suggesting that the antimicrobial activity of the phenotypically positive isolates should necessarily be due to another enterogenic or non-enterogenic compound. A significant genetic variability was pointed out, but it was no possible to link the enterocin phenotypes and genotypes with the strain origin. No relation with the geographical origin or the period in which the strains were isolated was also found with regard to the VOCs production and very different enzymatic activities among strains was detected. The major volatile compounds produced were: ethanol, diacetyl, acetoin, acetic and benzoic acids. The results of the present study suggested that a polyphasic approach, combining different phenotypical and genotypical methods, may represent an essential tool to obtain a more effective, accurate and exhaustive investigation of the microbial typing. Finally, even if RSA-PCR was proven to be a rapid, reliable and cost-effective alternative to other PCR methods for the microbial identification and typing, the possibility to compare RSA-PCR results obtained with different thermal cyclers and Taq DNA polymerases has not been investigated effectively. Four models of thermal cyclers of 3 different commercial brands and 4 brands of Taq DNA polymerase were evaluated for their effects on the reproducibility of the RSA-PCR. Five reference LAB strains (St. thermophilus, Lb. helveticus, Lb. delbrueckii subsp. lactis, Lb. delbrueckii subsp. bulgaricus and Lb. fermentum) and a DNA mixture, obtained combining together the DNAs extracted from each reference strain in the same ratio, were used in the experiment. A wide variety of RSA-PCR profiles in terms of band number and size were observed in relation to thermal cycler and Taq DNA polymerase tested, highlighting the relevant influence of these two variables on RSA-PCR reproducibility. It is therefore recommended to choose, within each laboratory, appropriate operating procedures in accordance with one’s equipment and reagents.

National Dairy Equipment (Pty) Ltd (NDE) is a privately owned stockist and distributor of stainless steel products and is a respected player in the South African stainless steel industry. NDE operates from within all four major cities in South Africa namely, Johannesburg, Cape Town, Port Elizabeth, and Durban. The organisation, with its wide range of corrosion resistant products, serves industries such as the architecture and construction, automotive, catering, and food and beverage industry. With the stainless steel industry growing in terms of the number of competitors, NDE performs a number of functions in order to achieve customer satisfaction. The general purpose of the study was to indentify the attributes that would act as drivers of customer satisfaction at NDE. Five attributes were identified namely, Service quality, Trust and commitment, Product quality, Commercial aspects and Reliability. The results of this study could assist managers at NDE in improving service delivery to customers. The literature study provided an overview of overall customer satisfaction and possible measurement models for customer satisfaction. Measurement models included, SERVQUAL, SERVPERF, the Two-factor theory, the Kano model and the Three-factor model. The latter proved to be of particular importance to the study as the model was used to classify the identified drivers into basic, performance and excitement factors. Furthermore, a literature review was provided based on each of the identified potential drivers of customer satisfaction. The empirical data needed to complete the study was collected by means of a survey, using a self-administered questionnaire. The questionnaire was distributed by sales representatives at NDE. A total of 320 useable questionnaires were received. The study revealed the following: each of the five proposed attributes had a positive relationship with overall customer satisfaction,thus all five attributes were confirmed as drivers of customer satisfaction at NDE. Commercial aspects and Reliability were classified as basic satisfiers. Trust and commitment was classified as a performance satisfier, and Service quality was identified as the only excitement satisfier. Product quality did not receive any classification. All importance mean scores were higher than the corresponding satisfaction mean scores. This study contributed to the existing body of literature and is seemingly the first of its kind in the South African stainless steel industry. The study is also the first to attempt the measurement of overall customer satisfaction levels at NDE. The methodology used in the current study can be applied to stainless steel industries internationally, in order to verify whether the confirmed drivers would also act as drivers of satisfaction in a similar industry elsewhere in the world.

The antioxidant activity of an ethanol extract prepared from cranberries was investigated using the oxygen radical absorbance capacity (ORAC) assay, as well as in a model food emulsion representative of dairy-based emulsions. The cranberry extract exhibited 348.31 ± 33.45 Trolox equivalents (TE)/g in the hydrophilic ORAC assay. In the model food emulsion consisting of 25% lipid stabilized by sodium caseinate, the extract was readily incorporated at the homogenization step until a pH of 5.6 was attained without causing emulsion destabilization. Under thermal conditions (50ºC), the lag phase prior to propagation of conjugated dienes (CD) in all cranberry emulsions at pH 5.6 was significantly extended relative to untreated controls (P < 0.05). The formation of secondary lipid oxidation products (hexanal and pentanal) in sunflower oil emulsions became significantly reduced (P < 0.05), but only after 64 hours of incubation. In contrast, the development of hexanal and pentanal in butterfat emulsions were significantly reduced (P < 0.05) over the entire incubation period. Increasing the level of cranberry extract in all emulsions beyond a final pH of 5.6 had an adverse effect on emulsion stability, and this was met with a drop in oxidative protection. The acidity of the cranberry extract made it well-suited for use in a fresh cream cheese product, which requires the production of acid during manufacture. The cranberry extract was homogenized into a cream cheese premix consisting of milk and cream until a pH of 5.6 was reached. Cheese produced from 1.18 g extract/100 g premix had a light pink color that remained stable over 50 days of storage at 4ºC. The cheese curd was found to retain over 98% of phenolics from the extract after separation of the whey. The level of CD and the peroxide value in the final product were significantly lower (P < 0.05) as compared to the untreated control cream cheese, after two weeks of storage at 4ºC. This research shows for the first time that a cranberry extract rich in bioactives can provide color and flavor to fresh dairy products while also acting as a useful preservation agent.

Cardiovascular disease (CVD) and type II diabetes are the leading causes of morbidity and mortality worldwide. The impact of diet on novel, independent predictors of CVD, such as arterial stiffness, is of great interest. Findings from the Caerphilly Prospective Study, in which 2,512 men were followed up for up to 23- years, demonstrated a positive prospective association between saturated fatty acid (SFA) intake and arterial stiffness, while poly-unsaturated fatty acid (PUFA) intake was inversely associated. Furthermore, this cohort identified that dairy product intake (excluding butter) and milk were inversely associated with prospective arterial stiffness and systolic blood pressure (SSP) respectively. As milk was found to be cardio-protective, but SFA intake was associated with greater CVD risk, a study in dairy cows was designed to lower proportions of SFA in milk fat, with the aim of improving the ability of milk and dairy product consumption to reduce CVD risk further. This study identified that feeding dairy cows high proportions of maize silage (MS), as well as supplementation with extruded linseed, compared to non-supplemented, high grass silage (GS) diets, led to significantly lower proportions of milk SFA and higher proportions of monounsaturated fatty acids (MUFA) and PUFA in milk. A high SFA, low MUFA/PUFA dairy lipid, a low SFA, high MUFA/PUFA dairy lipid, and individual dairy FA were tested in an in vitro study using healthy and type II diabetic human aortic endothelial cells (HAEC) to determine possible beneficial effects of this strategy in relation to vascular function.

There is accumulating evidence on differences in the link between types of dairy products and cardio-metabolic health, but inconsistent findings limit the field. In my PhD project, I undertook an epidemiological investigation comprising inter-related but distinct themes evaluating aspects of nutritional, molecular and genetic epidemiology to advance scientific understanding. I undertook research to describe dairy consumption patterns over time by evaluating nationally-representative data of the United Kingdom National Diet and Nutrition Survey. I observed significant time trends for specific dairy types and groups, which were different among different groups of people e.g. adults younger than 65 years or elderly people. Using data from the large Fenland (n~12,000) and EPIC Norfolk (n~25,000) studies, I investigated associations of total and types of dairy consumption with markers of metabolic risk and adiposity as potential pathways to cardio-metabolic disease. The analyses showed differential associations of dairy types and groups mainly with markers of adiposity and lipidaemia. I explored the potential of objective markers to assess dairy consumption, by examining metabolomics profiles and blood fatty acids to identify a set of biomarkers predicting dairy consumption and prospective associations of the identified biomarkers with type 2 diabetes risk. I was able to develop and validate metabolite scores reflecting consumption of some dairy products and observed inverse associations between some of these scores and type 2 diabetes incidence. I analysed genetic determinants of dairy consumption, using a genome-wide association study in the UK Biobank (n~500,000) and identified single nucleotide polymorphisms predicting milk, cheese and total dairy consumption. Overall, this PhD work contributed towards (1) a more precise description of dairy consumption patterns in the UK, (2) hypothesis formulation for potential biological pathways linking to cardio-metabolic disease, (3) discovery of metabolite scores as potential dairy biomarkers and (4) hypothesis formulation for potential genetic predictors of dairy consumption.

College students engage in poor dietary behaviors which put them at risk of weight gain and subsequent future health problems. This necessitates implementation of nutrition interventions which target dietary behaviors in college students so that healthy dietary patterns can be adopted and maintained through adulthood. Dairy intake is one of the many dietary behaviors which has declined substantially in young adults (18-30 years of age) - a period which includes the college age population. According to 2005 dietary guidelines for Americans three or more than three servings of low-fat/fat-free dairy foods is recommended for young adults, which is associated with overall nutrient quality of the diet and several health benefits. Still dairy consumption in this age group is below two serving per day. As emerging adults, college students may be more receptive to health advice than young adults older than traditional college years whose health habits are more established; nutrition intervention to improve dairy intake may be well received. Psycho-socio variables from Social Cognitive Theory (self regulation, social support, self-efficacy and outcome expectations) have been associated with adoption of healthy eating habits in college students and are associated with dairy consumption in adolescents. A series of studies were conducted to assess and improve dairy intake in college students by changing the mediating psycho social variables from Social Cognitive Theory (SCT) of behavior change including social support, self efficacy, outcome expectations and self regulation. A pilot web based nutrition education intervention was conducted to improve dairy intake in college students using SCT. The aim of this study was to evaluate the effect of the intervention on self efficacy, outcome expectations, self regulation, behavior and dairy product intake. Two hundred and ninety four students participated in the study and data on dairy intake and SCT variables were collected using 7 day food records and questionnaires. A 5 week electronic mail intervention was conducted. The intervention improved some social cognitive factors such as self regulation and self efficacy regarding increased dairy intake in college students, though dairy intake did not change. Next, to understand factors associated with dairy intake in college students, qualitative data were collected using focus group discussions (n=3), elicitation interviews (n=13) and online asynchronous discussion forums (n=3) using identical questions. Fifty students participated in the study and the aim was to identify relevant barriers, motivators and facilitators to dairy and low-fat dairy consumption. The results indicated that there was widespread lack of clarity regarding amount of dairy/calcium required and whether students felt they were getting enough. Major barriers to consuming dairy foods included short shelf life, storage issues, taste and accessibility to dairy foods on campus. Major facilitators included constant reminders, knowing immediate benefits, more accessibility and breakfast consumption. The aim of the final study was to improve social support, self efficacy, outcome expectations, self regulation and behavior related to dairy intake in college students using Social Cognitive Theory (SCT). One hundred and ninety one students participated in the study which included 8 week electronic mail intervention. Data collected included 7 day food records and for dairy intake and questionnaires for SCT variables. The intervention resulted in significant improvement in total dairy intake and use of self regulation strategies by college students. Taken together, these results suggest that theory-based nutrition education interventions can improve nutrition behavior in college students, a population prone to poor dietary habits. Developing mastery experiences to improve self efficacy may enhance self regulatory skills like goal setting, planning and monitoring to improve dairy intake in college students. Health care providers should aim at dietary behavior modification via theory based intervention.
Ph. D.

A study was conducted to investigate the use of bacterial numbers and metabolites for their Value in predicting potential shelf-life of pasteurized fluid milk. The study consisted of two phases. In the first phase, chemical inhibitors were evaluated for their ability to allow growth of gram-negative psychrotrophic bacteria while inhibiting growth of gram-positive organisms. Crystal violet, benzalkonium chloride, a mixture of crystal violet and benzalkonium chloride, and alkylaryl sulfonate were tested. These were incubated with milk samples separately inoculated with gram-negative and gram-positive bacteria, at 2l°C for 18 hours. Alkylaryl sulfonate allowed growth of gram-positive organisms. Crystal violet inhibited gram-positive organisms but was not as effective as the mixture of crystal violet and benzalkonium chloride, The inhibitor of choice was benzalkonium chloride as it inhibited growth of all gram-positive organisms tested and allowed growth of the gram-negative psychrotrophic organisms.

Master of Science

Time budgets, avoidance distance scores-related behaviour and milk yield of pasture-based Jersey, Friesland and crossbred cows. by Madodana Sunson Dodzi The study was conducted at the University of Fort Hare farm to determine the time budgets, the avoidance-related behaviour variables and their relationship with milk yield in three pasturebased dairy genotypes: Jersey, Friesland and crossbreed. Twenty one clinically health dairy cows aged between 52 and 55 months, in mid lactation and comprising of seven cows from each genotype were used in the study. The time spent on different activities (grazing, lying down, standing and others) at pasture was recorded using stop watches across four seasons. The behavioural responses of the three genotypes to humans were determined by recording their avoidance distance scores (AD), exit speed (ES), pen scores (PS), pen behaviour scores (PBS), plat form scores (PLS) and the occurrence of kicking (KCK) and stepping (SPG) during milking on four consecutive days in four seasons. Time spent standing was higher (P < 0.05) for Friesland compared to Jersey and crossbred during the hot-wet season. In the cool-dry season the Jersey spent more time (P < 0.05) grazing than the other breeds. The Friesland and crossbred on the other hand devoted most of their time lying down compared to Jersey in the cool- dry season (P < 0.05). There were season differences in time spent on all activities (P < 0.05). Time spent on grazing was longest in post-rainy seasonal and lowest in hot- wet season (P < 0.05). The longest lying down period was observed in the hot-dry season and lowest in hot-wet season (P < 0.05). iii Daily milk yield Varied (P < 0.05) with genotype with the Friesland and Jersey producing higher yield than the crossbred. The highest amount was produced in hot-dry and the least in hot-wet season. Milk yield was positively correlated (P < 0.05) with lying down. Standing was negatively correlated with milk yield (P < 0.05). The Friesland had the highest avoidance distance scores (P < 0.05) and the Jersey had the lowest avoidance distance scores in all seasons. There was an association (P < 0.05) between genotype and exit speed scores, pen scores and stepping behaviour scores. The Friesland exhibited the highest exit speed scores than the other breeds. The Jersey had the lowest (P < 0.05) kicking behaviour scores. There was a relationship (r = 0.64) between avoidance distance scores and exit speed. Exit speed scores were correlated with pen score(r= 0.23). Milk yield was significant related (r= 0.17) to the occurrence of kicking behaviour. The genotypes showed different levels of sensitivity to season and milk yield was influenced by breed and season. It can be concluded that time budgets vary with season and farmers need to adopt measures that buffer the effect of season on welfare of dairy cows. It can also be concluded that avoidance distance scores differs according to genotype with Jersey being more confident to humans than other two breeds. It is therefore recommended that provision of shades or cooling mechanism should be adopted to buffer the effects of hot-wet season. Improving quality of feed during the cool-dry season may be critical for Jersey cows. Finally positive handling of the dairy cows is recommended in order to improve the welfare and milk yield of pasture based dairy cows.

Skim, sweet buttermilk, and butter-derived aqueous phase components were used to re-emulsify low-melt butteroil into creams with a desired 20% milkfat. The implications of pasteurization process, homogenization sequence, and formulation on the physicochemical properties of reformulated and natural creams were investigated.

Creams homogenized prior to pasteurization had significantly (p<0.05) greater amounts of milkfat surface material per gram of cream and per gram of lipid compared to creams homogenized after pasteurization. Significantly (p<0.05) higher percentages of available phospholipid also were associated with the milkfat surface material of creams homogenized prior to pasteurization. Phosphodiesterase, a marker enzyme within the native milkfat globule membrane, was in significantly (p<0.05) higher activity relative to protein on lipid globule surface when cream was homogenized prior to pasteurization. Creams that underwent pasteurization prior to homogenization had significantly (p<0.05) higher protein load associated with the milkfat surface material.

Natural cream homogenized prior to pasteurization had significantly (p<0.05) greater milkfat surface material per gram lipid than natural cream homogenized after pasteurization and buttermilk / aqueous phase (AP) reformulated cream homogenized after pasteurization. In contrast, natural cream homogenized after pasteurization and BM / AP reformulated cream homogenized after pasteurization had significantly (p<0.05) greater amounts of protein per 10 mg of milkfat surface material than all other formulation / homogenization sequence combinations. In addition, natural cream homogenized prior to pasteurization, and skim milk (SM) reformulated cream pasteurized prior to or after homogenization had significantly (p<0.05) higher percentages of available phospholipid associated with the milkfat surface material than natural cream homogenized following pasteurization.

Pasteurization temperature had a significant (p<0.05) effect on apparent viscosity of natural and reformulated creams. All UHT pasteurized natural and reformulated creams had significantly (p<0.05) greater apparent viscosities at all shear rates monitored than HTST pasteurized natural and reformulated creams. At a failing curve shear rate of 692 s-1 UHT pasteurized cream reformulated with BM / AP had significantly (p<0.05) greater viscosity than UHT pasteurized natural cream and cream reformulated with skim component.

HTST pasteurized natural cream had significantly (p<0.05) greater viscosities than HTST pasteurized cream reformulated with skim component. Moreover, at a shear rate of 2769 s-1 and a rising shear rate of 1384 s-1 HTST pasteurized natural cream had significantly (p<0.05) greater viscosity than HTST pasteurized cream reformulated with buttermilk and aqueous phase.

Creams formulated with skim component showed significant differences in creaming stability after 7 days of storage. On the other hand, natural cream and cream reformulated with buttermilk and aqueous phase showed significant differences in creaming stability after 9 days of storage. HTST pasteurized creams had greater creaming stability than UHT pasteurized creams. All creams feathered in a pH range of 5.09 to 5.31. Homogenization prior to UHT pasteurization resulted in creams rated "out of specification" because of poor sensory quality on day 1. Other processing sequences resulted in creams within sensory specifications.
Master of Science

Thesis (MBA)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: The world population is growing rapidly and places additional pressure on the natural resources of the world. The increase in the world population leads to increasing focus on food security and the nutrition of the world population. Developed countries can only produce up to a certain level to satisfy the demand for food in the world. The additional production needs to come from countries where economic and agricultural development has been lagging. The research identified five major drivers of the future growth of agriculture. These drivers of future growth create opportunities for countries in Africa and help to address the development challenges for their different agricultural sub-sectors. The dairy industry in Southern Africa can play a significant role in addressing food security and nutritional needs of the growing population. Large numbers of livestock are present in Southern Africa because the landscape is lending itself to livestock farming and cultural believes see livestock as wealth in the hands of the owner. There are however serious challenges to address in order to achieve sustainable growth in the dairy industry in Southern Africa. The focus of the report is on the identification of the challenges in the dairy industry in Southern Africa, thus helping with the formulation of a growth strategy and business model. The report used a qualitative method of literature study to determine the challenges faced by the dairy industry in three Southern African countries, i.e. South Africa, Tanzania and Zambia. The contrasts between these countries are significant, but there are also many common elements and challenges. From this range of factors a set of key “challenges for action” has been derived, which are put forward as a basis for public and private sector efforts to strengthen growth in the sector. The list of challenges also assisted in the proposal of a business model to address part of the challenges of development in the dairy industry.

In this study, strains of probiotic bacteria have been selected for tolerance to low pH, bile, sucrose, oxygen in media and low storage temperatures. Lactobacillus acidophilus 2401 and Bifidobacterium infantis 1912 were selected as strains able to survive in these conditions. These two strains were then offered further protection from the adverse conditions of food processing and storage by microencapsulation in a calcium alginate and starch gel matrix. Encapsulation in calcium alginate increases survival in yoghurt. In cheddar cheese the free L. acidophilus 2401 and B. infantis 1912 cells survived better than the encapsulated cells, probably due to the dense nature of the cheddar cheese matrix combined with the encapsulation restricting the flow of the nutrients and metabolites between the outside environment and the cells. In ice cream survival was high, probably due to the high fat and solids nature of the ice cream combined with the low storage temperature. The trial results of the laboratory scale production was consistent with the survival results for yoghurt and cheddar cheese. Incorporation of encapsulated probiotic bacteria into ice cream and cheddar cheese was acceptable by sensory standards and largely unnoticeable in comparison with the same foods without capsules. The capsules were visible and able to be felt on the tongue when eaten in yoghurt causing the product to be disliked by the panellists.

In this study, strains of probiotic bacteria have been selected for tolerance to low pH, bile, sucrose, oxygen in media and low storage temperatures. Lactobacillus acidophilus 2401 and Bifidobacterium infantis 1912 were selected as strains able to survive in these conditions. These two strains were then offered further protection from the adverse conditions of food processing and storage by microencapsulation in a calcium alginate and starch gel matrix. Encapsulation in calcium alginate increases survival in yoghurt. In cheddar cheese the free L. acidophilus 2401 and B. infantis 1912 cells survived better than the encapsulated cells, probably due to the dense nature of the cheddar cheese matrix combined with the encapsulation restricting the flow of the nutrients and metabolites between the outside environment and the cells. In ice cream survival was high, probably due to the high fat and solids nature of the ice cream combined with the low storage temperature. The trial results of the laboratory scale production was consistent with the survival results for yoghurt and cheddar cheese. Incorporation of encapsulated probiotic bacteria into ice cream and cheddar cheese was acceptable by sensory standards and largely unnoticeable in comparison with the same foods without capsules. The capsules were visible and able to be felt on the tongue when eaten in yoghurt causing the product to be disliked by the panellists.
Master of Science (Hons)

Thesis (M.Sc.) (Hons.) -- University of Western Sydney, Hawkesbury, 2000.
A thesis presented for the fulfilment of Master of Science (Honours), Centre for Advanced Food Research, School of Science, Food and Horticulture, University of Western Sydney, Hawkesbury, December 2000. Spine title : Survival of probiotic bacteria in dairy foods. Bibliography : leaves 228-244.