Tesi sul tema "Meat quality"

Thesis (MSc)--Stellenbosch University, 2008.
ENGLISH ABSTRACT: The objectives of this study were threefold: (i) to investigate the effect of the replacement of pork fat with olive oil on the physico-chemical and sensory characteristics of ostrich polony; (ii) to investigate the effect of replacement of sodium tri-polyphosphate (STPP) with iota-carrageenan (CGN) on the physico-chemical and sensory characteristics of restructured cooked ostrich ham; and (iii) to investigate the effect of salt (NaCl) reduction on the physico-chemical and sensory characteristics of ostrich bacon. Five levels of olive oil were added to a polony formulation in 5% increments from 0 to 20%. Hardness, gumminess and shear force values decreased (P≤0.05) with increased levels of olive oil. The L* and b* values decreased (P≤0.05) with increased levels of olive oil producing lighter and more yellow products. Ostrich polony proved to have a favourable fatty acid profile in line with international recommended standards. A trained sensory panel found that the effect of increased levels of olive oil on had an effect (P≤0.05) on the sensory characteristics of colour; processed meat aroma and flavour; ostrich aroma; olive oil aroma; firmness and juiciness. A consumer panel found all the olive oil treatments to be acceptable. It can be concluded that olive oil can be used successfully for the production of low fat ostrich meat polony. In a restructured ostrich ham five decreasing levels of phosphate (0.7, 0.53, 0.35, 0.18 and 0%) were substituted with five increasing levels of carrageenan (0, 0.1, 0.2, 0.3 and 0.4%). The cooked yield of the restructured ostrich ham decreased significantly (P≤0.05) with decreased levels of phosphate. No tendencies in instrumental colour measurements with relation to decreased levels of phosphate were revealed. Hardness, cohesiveness and gumminess increased with decreased levels of phosphate. Ostrich ham had a favourable fatty acid profile and the latter is in line with international recommended standards. The trained sensory panel found that decreased levels of phosphate had a significant effect on the ham sensory characteristics of meat aroma and flavour; ostrich meat aroma and flavour and mealiness, but no significant effect on the spicy aroma and flavour. Three ham treatments with different levels of phosphate (0.7, 0.35 and 0%) were presented to a consumer panel. The consumer panel found the ham treatments with levels of 0.7 and 0.35% most acceptable. Carrageenan can be used to substitute phosphate at a level of 0.35% phosphate and 0.2% carrageenan in ostrich ham. Ostrich bacon was produces with five targeted salt (NaCl) levels of 3.5, 2.75, 2.0, 1.25, and 0.5%. Decreased salt levels had no significant effect on the L*, a* and b* values of the five treatments. Ostrich bacon had a favourible fatty acid profile. A trained sensory panel found that the effect of increased levels of salt had a significant effect on bacon sensory characteristics of ostrich aroma and flavour smoky bacon aroma and flavour and saltiness. A consumer panel found all the bacon treatments acceptable, with 2.75 and 2.0% being most likable. It can be concluded that, from a technical point of view, the salt content in ostrich bacon can be reduced successfully to produce ostrich bacon with low salt levels, although consumer preference for salt remains high.
AFRIKAANSE OPSOMMING: Die doelstellings van hierdie studie was drievoudig: (i) om die effek van die vervanging van varkvet met olyfolie op die fisiko-chemiese en sensoriese eienskappe van volstruispolonie te bestudeer; (ii) om die effek van die vervanging van natriumtripolifosfaat met iotakarrageenan op die fisikochemiese en sonsoriese eienskappe op die van hergestruktureerde volstruisham te bestudeer; en (iii) om die effek van sout (NaCl) vermindering op die fisiko-chemiese en sensoriese eienskappe van volstruisspek te bestudeer. Die polonie behandelings het uit vyf vlakke olyfolie bestaan wat by die polonie formulasie in 5% inkremente 0% tot 20% gevoeg is. Hardheid, taaiheid en skeurkrag het afgeneem (P≤0.05) met verhoogde vlakke van olyfolie. Die L*- en b*-waardes het afgeneem (P≤0.05) met verhoogde vlakke van olyfolie en uiteibdelik ‘n ligter en geler produk geproduseer. Die betrokke volstruispolonie behandelings het ‘n gunstige vetsuurprofiel wat in lyn is met internasionale aanbevole standaarde. ‘n Opgeleide sensoriese paneel het gevind dat die verhoogde vlakke van olyfolie ‘n betekenisvolle (P≤0.05) effek het op die kleur, geprossesseerde vleisgeur en -aroma, volstruis aroma, olyfolie aroma, fermheid en sappigheid. ‘n Verbruikerspaneel het gevind dat al vyf polonie behandelings aanvaarbaar is. Olyfolie kan dus suksesvol gebruik word in die produksie van laevet volstruispolonie. Hergestruktureerde volstruisham het bestaan uit vyf afnemende fosfaat vlakke (0.7, 0.53, 0.35, 0.18 and 0%) en vyf toenemende vlakke van karrageenan (0, 0.1, 0.2, 0.3 and 0.4%). Die opbrengs van gaar hergestruktureerde volstruisham het afgeneem (P≤0.05) met verlaagde vlakke van fosfaat. Geen betekenisvolle patroon is in instrumentele kleurmeting gevind nie. Hardheid, binding en taaiheid het toegeneem met afnemende fosfaat vlakke. Daar is bewys dat volstruisham ‘n gunstige vetsuurprofiel het wat in lyn is met internasionale aanbevole standaarde het. ‘n Opgeleide sensoriese paneel het gevind dat afnemende fosfaatvlakke ‘n betekenisvolle effek op die sensoriese eienskappe van volstruisvleis geur en aroma asook melerigheid, maar geen betekenisvolle effek op die speserygeur en -aroma gehad nie. Drie behandelings met verskillende fosfaat vlakke (0.7, 0.35 and 0%) is deur ‘n verbruikerspaneel vir aanvaaraarheid getoets. Die verbruikerspaneel het gevind dat die behandelings met 0.7 en 0.35% fosfaat aanvaarbaar was. Karrageenan kan dus gebruik word om fosfaat te vervang by ‘n vlak van 0.35% fosfaat en 0.2% karrageenan in volstruisham. Volstruisspek is geproduseet met vyf soutvlakke (NaCl), nl 3.5, 2.75, 2.0, 1.25 en 0.5%. Verlaagde soutvlakke het geen beteknisvolle effek op die L*-, a*- en b*-waardes van die vyf behandelings gehad nie. Volstruisspek het ook ‘n besonder gunstige vetsuurprofiel. ‘n Opgeleide sensoriese paneel het gevind dat die effek van verhoogde soutvlakke ‘n betekenisvolle effek het op die volgende sensoriese eienskappe: geur en aroma van volstruisvleis; geur en aroma van gerookte spek; en southeid. ‘n Verbruikerspaneel het gevind dat al die behandelings aanvaarbaar was, met die monsters met 2.75 and 2.0% sout as mees aanvaarbaar. In opsomming, die soutinhoud van volstruisspek kan uit ‘n tegniese oogpunt suksesvol verlaag word om ‘n produk met ‘n laer soutinhoud te produseer, alhoewel verbruikersvoorkeur vir sout hoog bly.

Genetic selection to increase lamb growth is advantageous in reducing the time it takes for lambs to reach market weight. However the effects of rapid growth on muscle fibre type, as indicated by oxidative capacity, is not clear. Muscle fibre type is intrinsically linked with attributes of meat quality, which are becoming increasing important to consumers. Therefore, changes to muscle fibre type through selection for growth may impact meat quality. Producers can impact lamb growth at any time during the growth period including the weaning (100 days) and post weaning time points (150 days). As not all lambs were weighed at these time points a growth curve was fitted to the live weight data of each individual animal to allow weight to be estimated at any time point during the growth period. Once estimates of weight and growth rate at the weaning and post weaning time points were obtained, the impact of growth on muscle fibre type and meat quality traits could be investigated. In the first experiment growth curves were fitted to live weight data for 18,185 lambs with weight data between birth and 300 days. Linear (cubic polynomial), nonlinear (Brody) and random effects models were fitted and the characteristics of the residual values examined to determine the best curve fit. The random effects model was hypothesised to have the lowest residual values as it is based on a population, rather than an individual fit, and is less biased when fitting growth curves to weight recordings from animals with different durations of data collection. However, the cubic polynomial fit had the lowest average residual values and the Brody fit had the highest. The difference between the residual values for the fit of each function was relatively small therefore the decision on which function to use was based on a variety of additional factors. As it is a population based fit, a random effects model accommodates missing weight recordings and different durations of data collection, which are common with industry data recording, without biasing the fit. A random effects model also allows environmental effects specific to the time of recording to be accounted for and can accommodate genetic differences in the shape of each animal's growth curve. Based on these characteristics the estimates of lamb weights and growth rates from the random effects model were used in this thesis. In the second experiment the impact of production factors on lamb weight at key time points in production were analysed. While several studies have published information on these effects the studies were generally small. Therefore, this analysis acted as a benchmarking for the magnitude of the effects, based on large data. The full expression of the post weaning weight breeding value is depressed with poor nutrition so an analysis was performed to determine the extent to which other forms of nutritional restriction, including lamb and dam factors such as birth type, dam breed and dam age, moderate the expression of the growth breeding value. As expected, factors such as multiple births, which act as a source of nutritional restriction, reduced the full expression of the growth breeding value and hindered lambs reaching expected weights. Muscle oxidative capacity is intrinsically linked to lamb growth and meat quality so in the third experiment the influence of genetic selection for growth on muscle oxidative capacity was examined. Oxidative capacity was indicated by the activity of the oxidative enzyme isocitrate dehydrogenase as well as the concentration of myoglobin in the muscle. As expected, genetic selection for growth reduced isocitrate dehydrogenase activity and myoglobin concentration. The reduction in oxidative capacity with increased growth was due to lambs tending toward a larger matures size and therefore being physiologically less mature at a given weight. The impact of lamb growth on oxidative capacity and meat quality has previously been estimated by the impact of the sire breeding value for growth on these traits or by using hot carcass weight as a proxy for whole of life growth. However the accuracy of these measures of growth is untested. The lamb weights and growth rates derived in the second experiment were used to determine the real impact of growth on oxidative capacity and meat quality. The impact of genetic selection on growth, or the use of hot carcass weight as a proxy for the impact of growth on meat traits, were both shown to be inadequate in quantifying the magnitude of the effect of growth on meat quality traits and indicating how the effect of growth varied with time. In the fourth experiment the impact of lamb growth on intramuscular fat, shear force and consumer overall liking was examined. Intramuscular fat was increased and shear force was reduced with lamb growth. Intramuscular fat and consumer overall liking have a positive association however contrary to expectations growth had no impact on overall liking. This is likely to be due to influences on overall liking other than intramuscular fat. In the final experiment the impact of lamb growth in isocitrate dehydrogenase activity, myoglobin concentration, iron and zinc concentration and meat browning were examined. As hypothesised, myoglobin, iron and zinc concentrations increased with lamb growth. Contrary to expectations isocitrate dehydrogenase activity and meat browning were reduced with lamb growth. Meat browning was thought to reduce due to its strong association with oxidative capacity and thus the oxidative indicator enzyme inverse isocitrate dehydrogenase. These experiments have contributed to the sheep industry at a highly practical and adoptable level showing why the full potential of genetic selection for growth may not be realised and demonstrating the impact of growth on meat eating quality. Currently, increased growth in lambs, particularly in the early stages between birth and weaning has positive effects on meat quality however lambs had few weights recorded between these times so work needs to be done to characterise these associations.

Lo scopo principale di questa tesi è stato quello di indagare se gli effetti di: (i) razza (Bergamasca, Merinizzata Italiana e Sopravvissana); (ii) età di macellazione (40 vs 60 giorni) e (iii) stagione di allevamento (inverno vs autunno) abbiano influenzato le performance di allevamento, macellazione, qualità della carne e composizione di Acidi Grassi (FA) degli agnelli leggeri a marchio “Agnello del Centro Italia” IGP, allevati con sistema transumante nella regione Marche (Italia centrale). Gli agnelli delle razze oggetto di studio hanno mostrato performance di crescita, resa in carcassa e qualità della carne (es. caratteristiche fisiche e chimiche) simili, nonostante si siano evidenziate differenze in alcuni parametri (peso spalle, % proteina, cooking loss, TBARS e ORAC). L'effetto razza ha influenzato significativamente il profilo acidico della carne e del tessuto adiposo ed alcuni parametri legati al valore nutrizionale della carne (PUFA/SFA e indice trombogenico). Lo studio condotto per valutare l’effetto età di macellazione nella razza Bergamasca ha influenzato le caratteristiche quanti -qualitative della carcassa e della carne (drip loss, colore) e anche la composizione acidica del grasso. Considerando sempre la razza Bergamasca, l’effetto stagione di macellazione ha influenzato le caratteristiche della carcassa (corata) e della carne (pH e drip loss a 6 d), come anche il profilo FA della carne e del tessuto adiposo. Questo studio fornisce pertanto ulteriori informazioni sulla qualità di carcassa e carni di agnelli leggeri IGP “Agnello del centro Italia” ottenuti da razze differenti, allevati in stagioni diverse e macellati a differenti età e prodotti con sistema transumante nella regione Marche.
The main aim of the thesis was to investigate the effects of (i) breed (Bergamasca, Italian Merino and Sopravissana), (ii) slaughter age (40 vs. 60 days) and (iii) rearing season (winter vs. autumn) on growth, slaughter traits and meat quality, including fatty acid (FA) composition of “Agnello del Centro Italia” PGI light lambs produced under traditional transhumant sheep system adopted in Marche region (Central Italy). The lambs of the studied breeds showed similar growth performances, carcass traits and meat quality (i.e., physical and chemical characteristics), despite some differences in the investigated parameters that occurred (e.g. % crude protein, cooking loss, TBARS and ORAC). Breed significantly affected FA profile of meat and adipose tissue with Bergamasca showing less favourable meat FA profile (the lowest values of conjugated linoleic acid and the highest thrombogenic index). Higher slaughter age in Bergamasca lambs improved some carcass traits and physical characteristics of meat, it did not influence meat chemical composition or strongly affect meat FA profile, but it worsened chemical composition of adipose tissue. These results suggest 60 days as the optimal slaughter age for Bergamasca to produce slightly heavier carcasses without compromising the quality of lamb meat. Different rearing seasons influenced carcass traits (pluck) and meat quality (pH and drip loss after 6 days of meat storage). FA profile of both meat and adipose tissue was influenced by the rearing season with lambs reared in autumn having adipose tissue with better FA profile for human health. The research provides additional information filling the present gaps of knowledge regarding the quality of “Agnello del Centro Italia” light lambs produced under traditional systems in Marche region for local breeders and consumers.

The purpose of the PhD research was the identification of new strategies of farming and processing, with the aim to improve the nutritional and technological characteristics of poultry meat. Part of the PhD research was focused on evaluation of alternative farming systems, with the aim to increase animal welfare and to improve the meat quality and sensorial characteristics in broiler chickens. It was also assessed the use of innovative ingredients for marination of poultry meat (sodium bicarbonate and natural antioxidants) The research was developed by studying the following aspects: - Meat quality characteristics, oxidative stability and sensorial traits of chicken meat obtained from two different farming systems: free range vs conventional; - Meat quality traits of frozen chicken breast pre-salted using increasing concentrations of sodium chloride; - Use of sodium bicarbonate in comparison with sodium trypolyphosphate for marination of broiler breast meat and phase; - Marination with thyme and orange essential oils mixture to improve chicken meat quality traits, susceptibility to lipid oxidation and sensory traits. The following meat quality traits analyseswere performed: Colour, pH, water holding capacity by conventional (gravimetric methods, pressure application, centrifugation and cooking) and innovative methods (low-field NMR and DSC analysis) ability to absorb marinade soloutions, texture (shear force using different probes and texture profile analysis), proximate analysis (moisture, proteins, lipids, ash content, collagen, fatty acid), susceptibility to lipid oxidation (determinations of reactive substances with thiobarbituric acid and peroxide value), sensorial analysis (triangle test and consumer test).

The purpose of the PhD research was the identification of new strategies of farming and processing, with the aim to improve the nutritional and technological characteristics of poultry meat. Part of the PhD research was focused on evaluation of alternative farming systems, with the aim to increase animal welfare and to improve the meat quality and sensorial characteristics in broiler chickens. It was also assessed the use of innovative ingredients for marination of poultry meat (sodium bicarbonate and natural antioxidants) The research was developed by studying the following aspects: - Meat quality characteristics, oxidative stability and sensorial traits of chicken meat obtained from two different farming systems: free range vs conventional; - Meat quality traits of frozen chicken breast pre-salted using increasing concentrations of sodium chloride; - Use of sodium bicarbonate in comparison with sodium trypolyphosphate for marination of broiler breast meat and phase; - Marination with thyme and orange essential oils mixture to improve chicken meat quality traits, susceptibility to lipid oxidation and sensory traits. The following meat quality traits analyseswere performed: Colour, pH, water holding capacity by conventional (gravimetric methods, pressure application, centrifugation and cooking) and innovative methods (low-field NMR and DSC analysis) ability to absorb marinade soloutions, texture (shear force using different probes and texture profile analysis), proximate analysis (moisture, proteins, lipids, ash content, collagen, fatty acid), susceptibility to lipid oxidation (determinations of reactive substances with thiobarbituric acid and peroxide value), sensorial analysis (triangle test and consumer test).

The broad objective of this study was to determine the effects of natural antioxidants and thermal treatment on quality of meat from Bonsmara and non-descript cattle. A survey was conducted among 222 consumers in Alice (Fort Hare University community), Eastern Cape Province to determine the level of their awareness on application of antioxidants as preservatives in meat and meat products during storage. Representative samples of Muscularis longissimuss thoracis et lumborum and liver were collected from each carcass of Bonsmara (n=40) and non-descript (n=40) cattle reared on natural pasture to determine the effect of natural antioxidants and thermal treatment on their quality. The results from the survey revealed that 51.35 percent of the respondents had not heard about the use of antioxidant as preservatives in meat products. However, among the remaining respondents (48.65 percent) that were aware of antioxidant and its use as preservative, about 19 percent knew of natural antioxidants, 35 percent synthetic antioxidants while 46 percent had knowledge of both. The results further revealed that the majority of the respondents (82 percent) that had knowledge of natural antioxidants were concerned about the use of synthetic antioxidants in meat and meat products due to their health consequences. The in vitro antioxidant and antibacterial analyses of Bidens pilosa and Moringa oleifera leaf extracts revealed that they contain rich bioactive compounds. Furthermore, the addition of leaf extracts from Moringa oleifera (ML, 0.05 and 0.1 percent w/w) and Biden pilosa (BP, 0.05 and 0.1 percent w/w) to ground raw beef as a natural antioxidant were found to improve the physicochemical, oxidative stability and microbiological qualities of meat compared to the control (meat without extract) and BHT treatment (0.02 percent w/w) during 6 days storage at 40 C. Cattle breed did not have much effect on colour parameters. However, the overall pH of ground beef treated with extracts showed lower values than control and BHT treated beef. Also, ground beef samples containing extracts exhibited (P < 0.05) better colour stability, especially higher redness (a* values), than the control. The formation of TBARS in beef samples treated with extracts was significantly (P < 0.05) lower than the control and BHT treatment. The antibacterial assay of the extracts revealed an appreciable broad spectrum activity against the tested bacteria and microbial counts in ground beef samples compared to control and BHT group. Ground beef treated with plant extracts exhibited lower microbial and lactic acid bacterial counts (P < 0.05) at day 0 and 3 than control samples. Moreover, it was observed that application of sous vides thermal method did not significantly affect the fatty acids and mineral loss in beef and liver across the treatments. However, the total concentration of MUFA was lower in raw liver (20.11±2.38 - 21.08±1.23 percent) than in beef (40.22±1.90 - 42.53±1.29 percent), while total PUFA content were higher in liver (30.73±2.60 - 31.11±1.19 percent) than in beef samples (10.13±3.36 - 11.02±2.74 percent) (p < 0.05). The results also revealed that liver samples from Bonsmara and non-descript cattle had a higher percentage of intramuscular fat content of 4.67 ± 0.53 percent and 4.44 ± 0.53 percent respectively, and fat free dry matter of 27.51 ± 1.05 percent and 25.73 ± 1.05 percent, respectively, than the beef samples (p < 0.05). The concentrations of Mg (52.80±0.22 - 53.70±0.02mg/100g) and Zn (8.90±0.15 - 19.60±0.15mg/100g) were higher in beef than liver samples. The level of Ca (17.00±0.17 - 17.50 ± 0.17mg/100g) in liver was higher than that of beef samples. It was concluded that most consumers preferred the use of natural antioxidants in meat products than synthetic antioxidants due to their health risk. The effectiveness of M. oleifera and B. pilosa leaf extracts on meat quality also revealed that these plants are promising candidates as natural preservatives and their application should be considered in the meat industry. Lastly, findings from this study showed that application of the sous vide technique could protect meat products from nutritional loss during thermal treatment.

Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2006.
The aim of this study is to determine the effect of crossbreeding Zimbabwean Blue (ZB) and South African Black (SAB) ostriches on the morphological, physical, chemical and sensory quality of the meat. However, it is also necessary to determine the reproductive performance of these genotypes to scientifically support decisions made in the ostrich industry. In relation to reproductive traits and body measurements influencing these traits, results from the study suggested that ZB birds are between 9 and 15% heavier than their SAB contemporaries. Regarding SAB females, egg production was 47% higher, levels of shell deaths were lower, percentage of eggs not incubated was lower (P<0.01) and 84% more (P<0.01) chicks were produced in a season compared to their ZB contemporaries. Mates of SAB males produced a higher (P≤0.05) percentage of eggs not incubated and higher shell death percentages than the mates of ZB males. It has to be conceded that ZB females had a lower reproduction than SAB females, limiting the application of this genotype as a dam line in crossbreeding systems. With regard to morphological properties, the pure Blue genotype in comparison to the pure Black genotype differed significantly (P≤0.05), with 16 kg for live weight, 8.3 kg for carcass weight and 3.5 kg for leg weight. However, when comparing carcass yields (expressed as %) there were no significant differences (P>0.05) between genotypes. The M. gastrocnemius, M. femorotibialis accessorius, M. iliotibialis cranialis, M iliotibialis lateralis, M. iliofibularis and M. iliofemoralis showed significant genotype differences (P≤0.05) for individual muscle weight. When comparing the physical meat quality characteristics between the pure Blue genotype and the pure Black genotype, 70% of the muscles were higher (P≤0.05) in pH24, 50% of the muscles were redder (P≤0.05) and significantly less (P≤0.05) saturated in colour, 67% of the muscles had a lower (P≤0.05) percentage drip loss and 50% of the muscles had a lower (P≤0.05) percentage cooking loss. No significant (P>0.05) genotype differences were observed regarding the sensory quality of the meat. Regarding chemical meat quality characteristics, the percentage of moisture was higher and the percentage of lipid was lower for eight of the ten muscle groups from the pure Blue genotype. No significant differences (P>0.05) were found between genotypes or between muscles regarding the percentage of protein present in the meat. The highest (P>0.05) content of soluble collagen, myoglobin and cholesterol was found in the Blue x Black genotype, whereas the lowest percentage of the latter constituents was found in the pure Blue genotype. For the pure Black genotype the concentration of saturated fatty acids in the meat was lower (P≤0.05), the concentrations of total unsaturated fatty acids and desirable fatty acids in the M. illiofibularis were the highest (P≤0.05), while the concentration of monounsaturated fatty acids was also higher (P≤0.05) in both muscles of this genotype compared to the other two genotypes. Regarding both fat depots, the pure Black genotype had a lower (P≤0.05) concentration of saturated fatty acids, a higher (P≤0.05) concentration of monounsaturated fatty acids and total unsaturated fatty acids and a higher (P≤0.05) polyunsaturated:saturated fatty acid ratio. The percentage of desirable fatty acids in the abdominal fat depot was significantly higher (P≤0.05) for the pure Black and the Blue x Black genotype. In conclusion, crossbreeding between SAB and ZB ostriches seems to be a viable option to produce larger birds with more meat, without negatively affecting the overall quality of the meat.

The present thesis, which includes four main researches, aimed to study functional meat and meat products obtained from unconventional meat species, namely the rabbit and the ostrich. The first research tested the single and combined dietary supplementation with 5% Spirulina (Arthrospira platensis) and 3% Thyme (Thymus vulgaris) to growing rabbits for 3 and 6 weeks, and it is articulated in four different subchapters. The first subchapter considered the effect on total tract apparent digestibility of nutrients and on the performances of growing rabbits and showed that that single and combined supplementation with Spirulina reduced the nutritive value of the diets. Despite this, no substantial effect on growth performance and health status, was observed. Future studies should take into consideration feed processing technology, pelleting, storage and packaging conditions, as they may reduce or nullify the nutrient and functional compounds’ availability. Moreover, Spirulina and/or Thyme effect on health status should be tested under poorer sanitary conditions. The second subchapter studied the effects on growing rabbit carcass composition, meat and bone rheological traits, and the vitamin B12 content of Longissimus dorsi (LD) meat. Spirulina was confirmed as a rich source of vitamin B12 that was successfully transferred into LD meat, thus demonstrating its value as an effective natural supplement in producing food fortified with this vital element. With this exception, the supplement as well as and the duration of treatment had no effect on the considered traits. The third subchapter evaluated the effect on rabbit meat during retail display. Thyme improved colour parameters and reduced exudative losses during a simulated retail display, also considering a shorter supplementation period. This would positively impact consumers at the time of purchase as well as farmers demand to limit production costs. Differently, Spirulina had no effect on oxidative stability of rabbit meat, maybe for the poor absorption from the gut as a result of interference on uptake of antioxidants by Spirulina, or maybe because dietary level of Spirulina was not adequate for rabbits requirements. The fourth subchapter studied the effects on raw and cooked rabbit meat quality, nutrient true retention and protection against oxidative stress conditions. The dietary inclusion of Spirulina improved the FA profile of the Longissimus dorsi and hind leg meat by significantly increasing γ-linolenic acid content. Thyme improved the oxidative stability of raw and freeze-dried HL meat but not that of cooked meat. As for the shelf-life trial, Spirulina was not observed to improve the oxidative stability of rabbit meat subjected to severe oxidative stress. The second research of the present thesis, aimed to evaluate the effect of the dietary single or combined supplementation with different natural additives (Oregano, Rosemary, vitamin E and Saccaromyces cerevisiae) on the performance of growing rabbits, the nutritional composition and oxidative stability of their meat and on their hind leg bone traits. The results of this research demonstrated that an adequate supplementation with natural antioxidants can also have a positive effect on productive performance and meat quality. The fifth chapter evaluated, for the first time, the unfermented and fermented rooibos (Aspalathus linearis) in preventing lipid oxidation in ostrich meat patties and ostrich salami. This plant showed interesting and promising antioxidant potential when applied to meat products, even if further study are necessary to deeply investigate long-term effects. The sixth chapter studied the effect of two different fat inclusion levels, NaCl contents and two LAB starter cultures on the weight loss, proximate composition and cholesterol content of ostrich salami ripened for 10 and 20 weeks. A lower fat content consistently shortened ripening time, thus being a positive aspect in terms of productivity, and it determined a higher nutrients concentration compared to high fat salami. Reducing the NaCl inclusion, retarded the weight loss of the product of about 1 week, without affecting its proximate composition. Finally, the metabolic activity of tested LAB starter cultures seemed to be influenced by the fat inclusion level, ultimately affecting the healthiness of the products at 10 weeks of ripening
La presente tesi si compone di quattro ricerche principali e si propone di studiare carne e prodotti carnei funzionali ottenuti da specie non convenzionali, lo struzzo e il coniglio. La prima ricerca ha testato l’inclusione singola o combinata, per 3 o 6 settimane, con il 5% di Spirulina (Arthrospira platensis) ed il 3% di Timo (Thymus vulgaris) nella dieta di conigli in accrescimento. Questo primo capitolo si articola in quattro sottocapitoli. Il primo ha considerato l’effetto sulla digeribilità apparente delle diete e sulle prestazioni produttive di conigli in accrescimento e ha evidenziato che l’inclusione separata o combinata di Spirulina ha ridotto il valore nutritivo delle diete. Nonostante ciò, non è stato osservato alcun effetto sulle prestazioni produttive e sullo stato di salute degli animali. Studi futuri dovranno considerare la tecnologia di produzione del mangime, la pellettatura e le condizioni di confezionamento e stoccaggio, in quanto potrebbero ridurre o nullificare la disponibilità di componenti nutritivi e funzionali. Inoltre, l’inclusione di Spirulina e/o Timo dovrebbe essere testata in condizioni sanitarie più critiche. Il secondo sottocapitolo ha valutato l’effetto dell’inclusione di Spirulina e Timo sulla composizione della carcassa, le caratteristiche reologiche di carne ed ossa ed il contenuto di vitamina B12 del Longissimus dorsi (LD). Spirulina ha confermato di essere una fonte di vitamina B12, la quale è stata trasferita con successo nella carne del LD. Spirulina ha quindi dimostrando il suo valore quale additivo naturale per produrre alimenti fortificati con questo elemento. Per quanto riguarda gli altri aspetti considerati nella presente ricerca, gli additivi naturali testati non hanno avuto alcun effetto. Il terzo sottocapitolo ha studiato la “shelf-life” della carne fresca di coniglio durante una simulazione di esposizione finalizzata alla vendita. Il timo ha migliorato il colore e ridotto le perdite essudative della carne, anche quando è stato somministrato per il periodo più breve. Questo risultato da un lato è in grado di influenzare positivamente il consumatore al momento dell’acquisto, e dall’altro va incontro alle esigenze dell’allevatore di limitare i costi di produzione. Al contrario, Spirulina non ha avuto alcun effetto sulla stabilità ossidativa della carne, forse per uno scarso assorbimento intestinale dovuto all’interferenza degli antiossidanti presenti nella Spirulina stessa, oppure perché il livello di inclusione nella dieta non era adeguato alle esigenze dei conigli. Il quarto sottocapitolo ha testato l’effetto sulla qualità della carne cruda e cotta, sulla ritenzione reale dei nutrienti e sulla protezione nei confronti di condizioni di stress ossidativo. L’inclusione di Spirulina ha migliorato il profilo acidico del Longissimus dorsi e dell’arto posteriore di coniglio, attraverso l’aumento del contenuto dell’acido grasso γ-linolenico. Il Timo ha migliorato la stabilità ossidativa della carne dell’arto posteriore cruda e liofilizzata, ma non quella della carne cotta. Come era stato osservato nel precedente esperimento sulla “shelf-life” della carne di coniglio, Spirulina non ha migliorato la stabilità ossidativa della carne sottoposta a stress ossidativo intenso. Il secondo capitolo della presente tesi, ha considerato l’effetto dell’inclusione singola o combinata con diversi additivi naturali (Origano, Rosmarino, vitamina E e Saccaromyces cerevisiae) sulle prestazioni produttive di conigli in accrescimento, la composizione nutrizionale e la stabilità ossidativa della carne nonchè sulle caratteristiche ossee degli arti. I risultati di questa ricerca hanno dimostrato che un’adeguata inclusione di antiossidanti naturali nella dieta di conigli in accrescimento ha avuto un effetto positivo anche sulle prestazioni produttive e sulla qualità della carne. Il quinto capitolo, invece, ha studiato per la prima volta l’applicazione di rooibos (Aspalathus linearis), fermentato e non, sulla carne e prodotti derivati. In particolare, è stata valutata la sua capacità di prevenire l’ossidazione lipidica in polpette e salami di struzzo. I risultati hanno rivelato un interessante e promettente potenziale antiossidante di questa pianta nei confronti dei prodotti carnei testati. Tuttavia, sono necessari ulteriori studi per esaminarne l’efficacia a lungo termine. Il sesto ed ultimo capitolo, ha valutato due diversi livelli di grasso e NaCl, e due diversi starter microbici, sulle perdite di peso, composizione centesimale e contenuto di colesterolo di salami di struzzo stagionati per 10 e 20 settimane. Un minore contenuto di grasso ha ridotto considerevolmente il tempo di stagionatura, essendo quindi un aspetto positivo in termini di produttività, e ha determinato una maggiore concentrazione di nutrienti rispetto al salame preparato con il più alto livello di grasso. La riduzione del contenuto di NaCl ha ritardato le perdite di peso dei salami di 1 settimana, senza tuttavia modificare la composizione centesimale del prodotto. Infine, l’attività metabolica degli starter microbici testati è sembrata essere condizionata dal contenuto di grasso del salame e ciò, a 10 settimane di stagionatura, ha influenzato la salubrità del prodotto

The objective of this study was to determine if increasing the forage level and feeding grain whole as opposed to dry-rolled is a feasible alternative to high energy rations with a similar age at time of slaughter. Steers were fed either twenty or forty percent forage, with whole or dry-rolled corn. There were no differences in fat thickness, longissimus area, KPH, marbling, USDA quality grade, Warner-Bratzler shear force, or cook loss. Cattle fed high forage and whole corn tended to have lower hot carcass weights. Additionally, the forty percent forage treatment tended to have lower USDA yield grades, and had darker colored steak. Also, steaks from the dry-rolled corn treatment had steaks that were redder, and more yellow. Results from this study suggest that increasing forage level, and corn processing might not result in significant differences in carcass characteristics or meat tenderness, but could negatively impact meat color.

La carne de cerdo es la más consumida mundialmente. Los programas de mejora animal se han centrado en realizar una producción sostenible y eficiente mejorando tanto los caracteres de reproducción, como de crecimiento y calidad de la carne. Actualmente no se dispone de un conocimiento completo sobre la base genética que determina estos caracteres de producción y por este motivo el objetivo principal de esta tesis consistió en profundizar en los mecanismos moleculares que determinan los caracteres de crecimiento y calidad de la carne. Los genes FABP4 y FABP5 fueron evaluados como genes candidatos para la composición de ácidos grasos en músculo y grasa dorsal. Los animales portadores del alelo C para el polimorfismo FABP4: g.2634_2635insC mostraron un mayor contenido intramuscular de ácidos grasos C16:0 y C16:1(n-7) y, un menor contenido de C18:2(n-6) y una mayor expresión del gen FABP4 en grasa dorsal. Dicho polimorfismo se encuentra dentro de una diana de unión para el gen PPARG pudiendo este factor nuclear determinar las diferencias de expresión observadas. Respecto la expresión del gen FABP5 en músculo, se detectaron regiones asociadas en los SSC4, SSC6, SSC9 y SSC13. Sin embargo, no se observó una clara asociación de genotipos del SNP FABP5: g.3000T> G con la composición de ácidos grasos. Con el objetivo de explorar el transcriptoma del músculo para identificar genes y rutas metabólicas relacionadas con el contenido y la composición de ácidos grasos en músculo, se secuenció el ARN de dos grupos de animales que diferían en estos caracteres. Se identificó un total de 131 genes diferencialmente expresados entre grupos en su mayoría relacionados con las rutas del metabolismo lipídico. El análisis funcional mostró una menor captación de glucosa y una inhibición de la lipogénesis en los animales con un mayor contenido en PUFA. Los enfoques utilizados hasta ahora para el análisis de los caracteres complejos implican generalmente varios genes con efectos pequeños y no consideran las interacciones funcionales. Por esta razón, se decidió aplicar un enfoque de redes génicas basada en el análisis de co-asociación entre SNPs para el estudio de caracteres relacionados con el crecimiento, la conformación y el engrasamiento. Se identificaron tres factores de transcripción, PRDM16, ELF1 y PPARG, como principales reguladores de la red. Además, 54 de los genes identificados en la red pertenecían a ontologías relacionadas con el crecimiento. Finalmente, con el objetivo de evaluar genes candidatos funcionales identificados en estudios previos de nuestro grupo afectando a caracteres de deposición y composición de ácidos grasos en músculo, se analizó la expresión de 45 genes en 114 animales. El eGWAS identificó 241 eSNPs distribuidos en 18 eQTLs. Tres de los 18 eQTLs presentaban variantes en cis, y en 16 de los eQTLs se identificaron zonas reguladoras en trans. Los resultados permitieron identificar potenciales reguladores y mejorar nuestro conocimiento sobre los mecanismos funcionales implicados en estos caracteres complejos.
Pork is the most consumed meat worldwide. The breeding programs have been working towards a sustainable pig production improving reproduction traits, growth and meat quality traits. The genetic basis determining these complex and economically important production traits remains elusive not being fully understood. In the present thesis we pursue to clarify the molecular mechanisms that determine growth and meat quality traits. The functional role of FABP4 and FABP5 genes in determining the fatty acid composition in muscle and backfat tissues was evaluated. Animals inheriting the C allele for FABP4:g.2634_2635insC polymorphism showed higher intramuscular content of C16:0 and C16:1(n-7) fatty acids and, decreased content of C18:2(n-6) fatty acid and higher FABP4 expression in backfat. Moreover, FABP4:g.2634_2635insC was located inside a PPARG binding site suggesting a role of this nuclear receptor in the regulation of FABP4 gene expression. The FABP5:g.3000T>G SNP was the most significant marker for intramuscular percentages of C18:1(n-9), C18:2(n-6), and MUFA. However, this variant was not associated with FABP5 gene expression, being FABP5 gene expression in muscle regulated by other genomic regions located on SSC4, SSC6, SSC9 and SSC13. Aiming to identify genes and pathways affecting the intramuscular fatty acid composition, the muscle transcriptome of two groups of pigs with extreme phenotypes for these traits was analyzed. A total of 131 genes mostly related to lipid metabolism pathways were identified as differentially expressed between groups. The functional analysis showed that animals with a higher content of PUFA presented low fatty acid and glucose uptake resulting in an inhibition of the lipogenesis. Gene-by-gene approaches used until now are limited when analyzing complex traits usually implying several genes with small effects; moreover, they ignore functional interactions. For this reason, we decided to apply a gene network approach based on SNP-by-SNP co-association analysis to explore growth, conformation and fatness related traits. From the resulting network formed by 513 nodes and 639 edges, three transcription factors PRDM16, ELF1 and PPARG were likely to be the major regulators of this network. Moreover, 54 genes identified within the network belonged to growth-related ontologies. Finally, with the aim to evaluate functional candidate genes affecting intramuscular deposition and fatty acid composition traits from previous studies of our group, the mRNA expression of 45 genes was measured in 114 animals. The eGWAS identified 241 eSNPs distributed in 18 eQTLs. Three out of 18 eQTLs presented cis-acting variants and 16 eQTLs showed trans regulatory effects. The results highlighted putative key regulators and improved our knowledge in the functional regulatory mechanisms implicated in these complex traits.

Reducing variation in tenderness is a goal for the meat industry. The objective of this study was to determine if different growth patterns, not caused by nutrient restriction, impacted carcass characteristics and tenderness. Simmental × Angus steers (n = 18) reared under similar conditions, fed in the same pen at the feedlot, were allocated into fast (n = 9) and slow (n = 9) growing groups based upon four sets of weight data. After slaughter, carcass data were obtained. The striploin was removed, cut into steaks, and aged for 1, 3, 7, 14, and 21 days. For each aging period, one steak per steer underwent evaluation of shear force and MFI. Myofibrils were isolated from aged muscle samples and protein degradation was visualized with the use of SDS-PAGE. Carcass weight (P< 0.0001) and LD area (P = 0.0093) were significantly affected by growth rate. Shear force (P = 0.0003) and MFI (P< 0.0001) were significantly affected by length of aging, but not by growth rate (P≥ 0.3184); nor was there a significant interaction between growth rate and length of aging (P≥ 0.6555). Even though the shear force × growth rate finding was not statistically significant, shear force of steaks from fast-growing animals had a greater reduction in shear force values indicating a difference in early tenderization. A currently unidentified protein with a molecular weight between 130 and 100kDa was seen earlier postmortem in more tender muscle. This degradation was more apparent in muscle from fast growing steers. A 30kDa component also appeared earlier, and at a greater band intensity, in more tender muscle. Degradation of the 30kDa component was also more evident in fast growing steers. These results suggest that there is a difference in protein degradation in muscle from animals with differing growth paths. The results of this study suggest that more research is warranted to identify differences in protein degradation due to growth rate and to elucidate the effect of growth rate on variation in tenderness.

Thesis (MScAgric)--University of Stellenbosch, 2007.
ENGLISH ABSTRACT: Although kudu (Tragelaphus strepsiceros) and impala (Aepyceros melampus) are found in the same geographical area, there is variation in their diets as kudu are predominantly browsers, feeding on tree and shrub leaves, while impala are known as mixed feeders as they graze and browse. Therefore this poses the question whether the diet would influence their meat quality. The objective of this investigation was to evaluate the physical measurements and chemical composition of M. longissimus dorsi, M. biceps femoris, M. semimembranosus, M. semitendinosus and M. supraspinatus for kudu and impala, two southern African antelope species. The effects of age (adult and sub-adult) and gender (male and female) were also determined. The sensory characteristics of the M. longissimus dorsi muscle for sub-adult kudu and impala were investigated. Correlations between the various physical measurements and chemical composition of the meat were verified. Physical measurements and chemical composition of the M. longissimus dorsi muscle were tested for correlations with the sensory ratings of the meat. Dressing percentage of impala (59.88%) (n=28) was higher than that of kudu (57.60%) (n=35). The main effects (species, gender and age) showed no differences for drip loss and cooking loss. However, muscles differed in terms of cooking loss with impala M. semitendinosus having the highest (38.28%) value and kudu M. longissimus dorsi having the lowest value (30.77%). For impala, the highest Warner–Bratzler shear (WBS) values were measured for M. semimembranosus (5.90 kg/1.27cmø), followed by M. biceps femoris, M. longissimus dorsi, and M. semitendinosus with the lowest WBS values measured for M. supraspinatus (3.61 kg/1.27cmø). All impala muscles had lower L* values and appeared darker in colour than kudu muscles, except for M. supraspinatus. Adult animals also had lower L* values than the sub-adult group. Kudu had significantly higher a* and b* values (more red) than impala. Chroma values were higher for kudu, thus appearing brighter in colour. The respective muscles of kudu and impala investigated differed significantly in terms of physical characteristics. However, gender and age did not have an effect on the physical measurements. Moisture content was higher in kudu meat (76.46%) than in impala meat (75.28%). Muscles differed for both moisture and fat content. The highest fat was found in M. supraspinatus followed by M. biceps femoris, M. semitendinosus, M. semimembranosus and M. longissimus dorsi. Protein content did not differ between species (kudu: 21.66%; impala: 22.26%), gender (male: 21.98%; female: 21.95%) and age groups (adult: 21.74%; sub-adult: 22.18%). Kudu M. longissimus dorsi (1.62%) had lower fat content than impala M. longissimus dorsi (2.22%) and female animals had a higher fat content than male animals. Sub-adults (1.20 ± 0.02%) had higher ash content than adults (1.10 ± 0.03%). The M. supraspinatus had the lowest protein and also the highest fat content, with M. semimembranosus having the lowest fat content but the highest value for protein. Myoglobin content did not differ between species, although females had higher (6.58 ± 0.20 mg/g) myoglobin content than males (5.11 ± 0.25 mg/g). Glycolitic muscles had the lowest myoglobin content with the highest values found in M. supraspinatus, an oxidative muscle. An interaction was noted between species and muscle for myoglobin content. Myoglobin content in impala M. longissimus dorsi was higher than that in kudu M. longissimus dorsi; however for all other muscles the myoglobin content was lower in impala. Gender did not affect mineral content. Potassium levels were highest for kudu while phosphorus was more prevalent in impala meat. Adult and sub-adult groups differed in terms of potassium, calcium and zinc content. Potassium and calcium content were higher for subadult animals while zinc content was higher in adult animals. In impala meat, stearic acid (22.67%) was the major fatty acid, followed by palmitic acid (16.66%). In contrast, oleic acid (24.35%) was the most profuse fatty acid in kudu, followed by linoleic acid (22.95%). The SFA’s as a percentage of the total fatty acids differed between impala (51.12%) and kudu meat (34.87%). Kudu meat had a higher concentration of total PUFA (38.88%) than impala (34.06%) meat. The PUFA: SFA ratio for kudu meat (1.22) was more favourable than that for impala meat (0.73). The ratio of n-6 PUFA’s to n-3 PUFA’s for kudu and impala were determined as 2.22 and 3.76 respectively. From the current findings it is evident that kudu and impala meat have advantageous fatty acid profiles and can be a healthy substitute for other red meats. Kudu meat (72.62 ± 1.86 mg/100g) had higher cholesterol than impala meat (55.35 ± 1.84 mg/100g). It is recommended that further studies be done in order to confirm the cholesterol content of kudu meat. Within species, no gender differences for any of the sensory characteristics tested were noted. The impala meat had a more intense game aroma than the kudu meat, while kudu meat was found to be more juicy than impala meat. It can therefore be concluded that the marketing of game meat should be species-specific as there are distinct flavour and aroma differences between kudu and impala meat.
AFRIKAANSE OPSOMMING: Alhoewel koedoes (Tragelaphus strepsiceros) en rooibokke (Aepyceros melampus) in dieselfde geografiese area voorkom, is daar variasie in hulle diëte. Koedoes is hoofsaaklik blaarvreters, terwyl rooibokke bekend staan as gemengde vreters aangesien hulle grassowel as blaarvreters is. Die vraag ontstaan dus of die verskil in diëet die kwaliteit van hulle vleis sal beϊnvloed. Die doel van hierdie ondersoek was dus om die fisiese metings en chemiese samestelling van die M. longissimus dorsi, M. biceps femoris, M. semimembranosus, M. semitendinosus en M. supraspinatus vir koedoes en rooibokke te bepaal. Die invloed van ouderdom (volwasse en onvolwasse) en geslag (manlik en vroulik) op hierdie eienskappe is ook geëvalueer. Die sensoriese eienskappe van die M. longissimus dorsi van onvolwasse koedoes en rooibokke is ook ondersoek. Korrelasies tussen die fisiese metings en chemiese samestelling van die vleis is ondersoek. Die fisiese metings en chemiese samestelling van die M. longissimus dorsi is getoets vir korrelasies met die resultate van die sintuiglike evaluering van die vleis. Die gemiddelde uitslagpersentasie van rooibokke (59.88%) (n=28) was hoër as die van koedoes (57.60%) (n=35). Daar was geen verskille in drupverlies en kookverlies vir die hoofeffekte (spesie, geslag en ouderdom) nie. Spiere het wel verskil in terme van kookverlies, met die hoogste waarde gemeet vir rooibok M. semitendinosus (38.28%) en die laagste waarde vir koedoe M. longissimus dorsi (30.77%). In rooibokke was die hoogste Warner- Bratzler skeurkrag waardes gemeet vir M. semimembranosus (5.76 kg/1.27cmø), gevolg deur M. biceps femoris, M. longissimus dorsi, en M. semitendinosus met die laagste Warner- Bratzler skeurkrag waardes gemeet vir M. supraspinatus (3.78 kg/1.27cmø). Alle rooibokspiere het laer L* waardes gehad en was donkerder van kleur as koedoespiere, behalwe vir M. supraspinatus. Laer L* waardes is ook verkry vir volwasse diere in vergelyking met onvolwasse diere. Die a* en b* waardes was hoër in koedoe- as in rooibokvleis, m.a.w. koedoevleis het rooier vertoon. Die onderskeie koedoe- en rooibokspiere het betekenisvol verskil in terme van fisiese eienskappe, terwyl geslag en ouderdom geen effek op die fisiese eienskappe gehad het nie. Voginhoud was hoër in koedoe- (75.52%) as in rooibokvleis (74.52%). Verkille tussen spiere is opgemerk vir beide vog- en vetinhoud. M. supraspinatus het die hoogste vetinhoud gehad, gevolg deur M. biceps femoris, M. semitendinosus, M. semimembranosus en M. longissimus dorsi. Geen verskille is opgemerk tussen spesies (koedoe: 21.66%; rooibok: 22.26%), geslagte (manlik: 21.98%; vroulik: 21.95%) en ouderdomme (volwasse: 21.74%; onvolwasse: 22.18%) in terme van proteϊeninhoud nie. Die vetinhoud van koedoe M. longissimus dorsi (1.62%) was laer as dié van rooibok M. longissimus dorsi (2.22%) en die vetinhoud van vroulike diere was hoër as dié van manlike diere. Onvolwasse diere (1.20 ± 0.02%) het ‘n hoër asinhoud as dié van volwasse diere (1.10 ± 0.03%) getoon. In terme van die onderskeie spiere het M. supraspinatus die laagste proteϊen- en die hoogste vetinhoud gehad, terwyl M. semimembranosus die laagste vet- en die hoogste proteϊeninhoud gehad het. Die mioglobieninhoud was nie beϊnvloed deur spesie nie, terwyl vroulike diere ‘n hoër (6.58 ± 0.20 mg/g) mioglobieninhoud as manlike diere (5.11 ± 0.25 mg/g) gehad het. Die M. supraspinatus, ‘n oksidatiewe spier het die hoogste mioglobieninhoud gehad, terwyl glikolitiese spiere die laagste mioglobieninhoud gehad het. ’n Interaksie tussen spesie en spier was opgemerk vir mioglobieninhoud. Rooibok M. longissimus dorsi het ‘n hoër mioglobieninhoud as koedoe M. longissimus dorsi gehad, terwyl die mioglobieninhoud vir al die ander spiere laer was in rooibokke. Mineraalinhoud was nie deur geslag beϊnvloed nie. Kaliumvlakke was hoër in koedoevleis, terwyl fosforvlakke hoër was in rooibokvleis. Kalium- en kalsiuminhoud was hoër in onvolwasse diere terwyl die sinkinhoud hoër was in volwasse diere. Steariensuur (22.67%), gevolg deur palmitiensuur (16.66%) was die mees algemene vetsure in rooibokvleis. In teenstelling hiermee was oleϊensuur (24.35%), gevolg deur linoleϊensuur (22.95%) die mees algemene vetsure in koedoevleis. Die totale versadigde vetsure was laer in koedoevleis (34.87%) in vergelyking met rooibokvleis (51.12%), terwyl die totale polionversadigde vetsure in koedoevleis (38.88%) hoër was as dié van rooibokvleis (34.06%). Die verhouding van n-6 tot n-3 poli-onversadigde vetsure vir koedoe en rooibok was 2.22 en 3.76 onderskeidelik. Hierdie resultate bevestig dat koedoe- en rooibokvleis oor ‘n vetsuurprofiel beskik wat ’n gesonde alternatief bied tot ander rooivleise. Die cholesterolinhoud van koedoevleis (72.62 ± 1.86 mg/100g) was hoër as dié van rooibokvleis (55.35 ± 1.84 mg/100g). Dit word egter aanbeveel dat verdere studies gedoen word om die cholesterolinhoud van koedoevleis te bevestig. Binne spesies was daar geen geslagsverkille vir enige van die sensoriese eienskappe nie. Rooibokvleis het ‘n meer intense wildsvleis aroma as koedoevleis gehad, terwyl koedoevleis meer sappig was as rooibokvleis. Hierdie resultate dui daarop dat die bemarking van wildsvleis spesie-spesifiiek moet wees aangesien daar defnitiewe geur en aroma verskille tussen koedoe- en rooibokvleis is.

Thesis (MSc (Consumer Science)--Stellenbosch University, 2008.
The purpose of this study was to investigate the chemical composition mineral and cholesterol content of the different cuts (breast, drumstick and thigh) of raw guinea fowl meat. The study also aimed at establishing the effect of cooking method on guinea fowl quality attributes by investigating the effect of different cooking methods on the chemical composition and sensory attributes of the different cuts. The effect of injecting a brine solution on the chemical composition and sensory attributes were also investigated. There were no differences in terms of moisture content of the various cuts raw guinea fowl meat The breast had significantly higher protein content when compared to drumstick and thigh (P<0.05). The fat content was similar for all the cuts (P>0.05). Whilst the drumstick had significantly the lowest value for ash content when compared to the thigh. Saturated fatty acids (SFAs) and total unsaturated fatty acids (TUFAs) were not different (P>0.05) in all the cuts. Drumstick had significantly higher monounsaturated fatty acids compared to other cuts (P<0.05), and it had the highest polyunsaturated fatty acids (P<0.05). The breast had the lowest (P<0.05) n-6 fatty acid value (44.25) and had relatively the lowest Polyunsaturated:Saturated (P:S) fatty acid ratio of 1.74 when compared to the other cuts. High n-6:n-3 ratios, ranging from 7.05 to 16.58, were also found in all the cuts. Cholesterol was lowest (P<0.05) in the breast. Seventeen amino acids were found, including the eight of the nine essential amino acids. Significant differences were found in amino acid values for the different cuts. Values of iron were significantly higher in the drumstick and thigh cuts (P<0.05), whilst drumstick had the highest zinc content of all the cuts (P<0.05). On investigating the effect of three cooking methods (baking-bag, foil-wrap, open-roasting at 140ºC for 65 minutes) on the chemical composition, the open-roasting method produced higher moisture content (P<0.05) consistently for all cuts, with the breast having the highest and the drumstick the lowest (P<0.05). The moisture content of the baking-bag method on the other hand was consistently the lowest (P>0.05). This effect was significant for the breast, which had lost the most moisture (P<0.05). The baking-bag method consistently resulted in a higher protein content, which is attributed to the higher moisture loss (P<0.05) in comparison with the other methods, resulting in a more concentrated product. With regard to the fat content no effect resulting from the cooking methods could be observed (P>0.05), but the cuts’ natural fat content was reflected especially in the open–roasting method (P<0.05) giving further support to the understanding that the open-roasting method indeed made the least inroads on the chemical composition of guinea fowl meat under these restraints: controlled for cooking time and temperature, internal temperature not controlled. All the cuts cooked according to all the methods, had the favourable >0.4 Polyunsaturated:Saturated fatty acids (P:S) ratio, ranging from 0.91 to 1.42 between cuts and treatments. The n-6:n-3 ratio was below the recommended beneficial value, namely <4:1, in all the cuts irrespective of all the cooking methods, ranging from 2.47 to 3.08. The study of the effect of the three cooking methods (baking-bag, foil-wrap and open-roast) on the sensory attributes of the breast meat revealed that aroma-intensity of the three cooking treatments did not differ significantly (P>0.05). Foil-wrap produced a more tender and juicier product (P<0.05), while, when using the baking-bag method, values for flavour decreased (P<0.05). It is proposed that a higher internal temperature (which was not controlled) was attained when using the baking-bag method (temperature and time controlled) resulting in loss of volatile flavour components. The effect of the three cooking methods (baking-bag, foil-wrap and open-roast) on the proximate composition (moisture, protein, fat and ash) of raw and cooked breast meat was investigated. As anticipated raw breast meat had higher moisture content (74.55%, P<0.05) than the cooked cuts, with open-roasting showing the highest (68.55%) value and foil-wrap close second (68.12%). These values differed significantly from the baking-bag method (66.06%, P<0.05). An investigation on the effect of brine infusion on the sensory attributes and chemical composition (proximate and fatty acid composition, and mineral content) of breast meat, baked in foil-wrap, was carried out using descriptive sensory analysis with the injected breast and the control as variable. There were no significant differences (P>0.05) between the injected and the control samples for any of the sensory attributes of aroma, tenderness, initial juiciness, sustained juiciness and flavour. Judge:treatment variations were observed for all the attributes, and samples differed for all attributes except for aroma. It is proposed that the use of the hand injector could not effectively distribute the brine solution, hence the recommendation to repeat the experiment using an electronic multineedle-injector. No effect was observed for the proximate composition (P>0.05). Further research pertaining to cooking methods of meat of free-range guinea fowl is recommended to address certain issues that have been highlighted.

Master of Agribusiness
Department of Agricultural Economics
Vincent Amanor-Boadu
HEB is a privately-held grocery retailer founded in 1905 in Kerrville, TX. Since then, HEB has grown to 399 stores in 155 communities. Although the majority of its operations have been in southern Texas, nearly 10 percent of HEB’s stores (39) are in Mexico. This may be considered an impressive feat since its entry into Mexico occurred in 1997 to take advantage of the growth opportunities in Mexico and the North American Free Trade Agreement involving Canada, the U.S. and Mexico. The research was conducted using primary data collected through a survey. Secondary data from the Shapiro Index were also employed to explain the observations from the survey. Econometric and statistical models were used in the analyses. Customer quality perception is an important metric for the retail industry. This research evaluates the effect of purchase history, frequency of shopping, price perception, quality and service changes through time on the quality perception of a meat department in a supermarket. The impact of additional labor was analyzed to determine the effect on those variables. The quality perception of the customers of other meat retailers in the same trading areas was also evaluated. The results of the study were then compared to the actual metric used to measure quality perception (Shapiro Index). The study found that the company has a significant higher quality perception than other supermarkets, that labor had a positive effect on quality and service change, customers noticed the change, and with time, it will increase their quality perception. The results show a different perception from customers than the Shapiro Index, customers do not notice a decrement on quality in the meat departments. Based on these results, a further research on the actual methodology used was performed, training and new purchasing specifications were applied to improve the intrinsic characteristics of the products and a new marketing campaign was launched based on quality and freshness.

The study has defined the position with regard to existing and evolving United Kingdom (UK) and European Union (EU) legislation, world trade agreements and institutions, global trade in chicken meat and market Quality Assurance (QA) standards in a series of peer-reviewed published papers and working papers. The development of global food supply chains can be a key driver in the harmonisation of international legislation, product and private assurance standards. Indeed compliance with legislation and retailer requirements has been a key market driver in the development of private assurance standards. The key objectives of the research were to examine current assurance schemes within the integrated poultry meat supply chain and the influence of regulation and external market drivers within the integrated poultry meat supply chain; develop and test a QA model for the poultry meat supply chain with a view to both baseline and higher level standards including the development of a business benchmarking system utilising a pre-requisite programme (PRP) and key performance indicators (KPI); and to assess the ability of the QA model to deliver regulatory and policy compliance whilst meeting varied business and market needs for an internationally traded product. This study has shown that a QA model is capable of providing a framework within which the poultry meat supply chain can operate. The legislative and performance requirements have been translated into quantifiable performance indicators which can be used to measure supply chain performance. This can assist differentiation of products at the point of consumption and give a quantifiable measure of the extrinsic value that has been added. This approach will therefore aid the communication of the benefits of differing methods of poultry meat production and afford the consumer the opportunity to make a more informed choice when purchasing meat products.

During postmortem metabolism, hydrogen ions accumulate in the muscle and gradually lower the pH from 7.2 to an ultimate pH near 5.6. The ultimate pH of meat is widely valued as an indicator of fresh meat quality as it directly affects the quality characteristics of color, texture, and water holding capacity. Therefore, our research was conducted to identify the processes responsible for determining ultimate pH. Pigs harboring the AMPK�•3R200Q mutation produce meat with extremely low ultimate pH (pH ~ 5.3) that is detrimental to quality. This phenomenon is often attributed to a greater glycogen content in muscle from the mutant pigs compared to wild-type pigs. However, our research indicated that greater glycolytic flux in muscle from these pigs causes a lower ultimate pH rather than greater tissue glycogen deposition. On the other hand, however, AMPK�•3R200Q pigs contain more mitochondria and retain greater oxidative capacity. Hence, we hypothesized that mitochondria may contribute to the lower ultimate pH in muscle of these pigs. To test our hypothesis, isolated mitochondria were incorporated into an in vitro system the mimics postmortem glycolysis. Mitochondria enhanced glycolytic flux and pH decline in the in vitro system similar to that of AMPK�•3R200Q pigs. After a series of experiments, we found that the causative agent for enhanced glycolytic flux is a soluble mitochondrial protein. In other experiments, mitochondrial F1-ATPase was found to be responsible for the majority of this effect, principally through promoting greater ATP hydrolysis at lower pH values, thereby allowing for greater flux through glycolysis. These data suggest that variations in ultimate pH may be more thoroughly explained and predicted by the abundance of mitochondria. Broiler pectoralis major muscle, which is a highly glycolytic muscle, possesses high ultimate pH (pH ~ 5.9) compared to pork and beef. We postulated that rapid carcass chilling reduces the flux through glycolysis, thereby causing premature termination of postmortem metabolism. Yet, chilling was only partially responsible for the high ultimate pH of pectoralis major muscle. However, we showed that pectoralis major of broiler chicken exhibits lower phosphofructokinase-1 activity compared to porcine longissimus lumborum muscle, which limits the flux through glycolysis.
Ph. D.
Consumer demand for high quality meat has increased dramatically over the past two decades. In order to meet this demand, it is crucial to understand factors that control the development of fresh meat quality characteristics. Consumers purchase meat based on color, but repeat purchases are also influenced by meat freshness, texture, and juiciness. These quality attributes develop after the animal has been harvested during the conversion of muscle to meat through a series of biochemical reactions. This conversion results in muscle acidification (pH decline) caused by the degradation of stored muscle energy that acidifies muscle. Normally, the muscle pH drops from a neutral value in living muscle to an acid value (~5.6) in fresh meat. In some cases, however, excessive acidification occurs and this can dramatically impact fresh meat quality characteristics. Our research program focuses on the mechanisms responsible for this extended acidification. To that end, we use mutant pigs known as RN– that produce meat with extremely low ultimate pH known as “acid meat”. While most believe that the extended pH decline in muscle of these pigs is a function of elevated energy in the muscle prior to harvesting, we showed that theses pigs have different muscle prior to harvest and this difference cause increased acidification during the transformation of muscle to meat. To investigate this issue further, we also examined the contribution of mitochondria (the powerhouse of the cell) to this process mainly because muscle from the RN– pigs containing around 50% more mitochondria compared to normal pigs. Curiously, we have shown mitochondria participate in this process. Because mitochondria require oxygen to function and harvesting animals disrupts oxygen delivery to the muscle, mitochondria were considered irrelevant to the development of meat quality characteristics. Our studies have definitively proved that mitochondria can contribute to meat quality and may be key in improving fresh meat quality.

Pig meat and carcass quality is a complex concept determined by environmental and genetic factors concurring to the phenotypic variation in qualitative characteristics of meat (fat content, tenderness, juiciness, flavor,etc). This thesis shows the results of different investigations to study and to analyze pig meat and carcass quality focusing mainly on genomic; moreover proteomic approach has been also used. The aim was to analyze data from association studies between genes considered as candidate and meat and carcass quality in different pig breeds. The approach was used to detect new SNP in genes functionally associated to the studied traits and to confirm as candidate other genes already known. Five polymorphisms (one new SNP in Calponin 1 gene and four additional polymorphism already known in other genes) were considered on chromosome 2 (SSC2). Calponin 1 (CNN1) was associated to the studied traits and furthermore the results reported confirmed the data already known for Lactate dehydrogenase A (LDHA), Low density lipoprotein receptor (LDLR), Myogenic differentiation 1 (MYOD1) e Ubiquitin-like 5 (UBL5), in Italian Large White pigs. Using an in silico search it was possible to detect on SSC2 a new SNP of Deoxyhypusine synthase (DHPS) gene partially overlapping with WD repeat domain 83 (WDR83) gene and significant for the meat pH variation in Italian Large White (ILW) pigs. Perilipin 1 (PLIN1) mapping on chromosome 7 and Perilipin 2 (PLIN2) mapping on chromosome 1 were studied and the results obtained in Duroc breed have shown significant associations with carcass traits. Moreover a study of protein composition of porcine LD muscle, indicated an effect of temperature treatment of carcass, on proteins of the sarcoplasmic fraction and in particular on PGM1 phosphorylation. Future studies on pig meat quality should be based on the integration of different experimental approaches (genomics, proteomics, transcriptomics, etc).

Pig meat and carcass quality is a complex concept determined by environmental and genetic factors concurring to the phenotypic variation in qualitative characteristics of meat (fat content, tenderness, juiciness, flavor,etc). This thesis shows the results of different investigations to study and to analyze pig meat and carcass quality focusing mainly on genomic; moreover proteomic approach has been also used. The aim was to analyze data from association studies between genes considered as candidate and meat and carcass quality in different pig breeds. The approach was used to detect new SNP in genes functionally associated to the studied traits and to confirm as candidate other genes already known. Five polymorphisms (one new SNP in Calponin 1 gene and four additional polymorphism already known in other genes) were considered on chromosome 2 (SSC2). Calponin 1 (CNN1) was associated to the studied traits and furthermore the results reported confirmed the data already known for Lactate dehydrogenase A (LDHA), Low density lipoprotein receptor (LDLR), Myogenic differentiation 1 (MYOD1) e Ubiquitin-like 5 (UBL5), in Italian Large White pigs. Using an in silico search it was possible to detect on SSC2 a new SNP of Deoxyhypusine synthase (DHPS) gene partially overlapping with WD repeat domain 83 (WDR83) gene and significant for the meat pH variation in Italian Large White (ILW) pigs. Perilipin 1 (PLIN1) mapping on chromosome 7 and Perilipin 2 (PLIN2) mapping on chromosome 1 were studied and the results obtained in Duroc breed have shown significant associations with carcass traits. Moreover a study of protein composition of porcine LD muscle, indicated an effect of temperature treatment of carcass, on proteins of the sarcoplasmic fraction and in particular on PGM1 phosphorylation. Future studies on pig meat quality should be based on the integration of different experimental approaches (genomics, proteomics, transcriptomics, etc).

The objective of the study was to determine the effects of Aloe ferox inclusion in drinking water on growth performance, blood biochemistry, physico-chemical characteristics, fatty acid profile and oxidative stability of broiler meat. The importance of A. ferox as a medicinal plant and factors that influence its utilization by communal poultry farmers were also investigated by use of a questionnaire survey. The survey revealed that the majority of respondents (84.6%) faced health challenges in their chickens and many relied (96.2%) on A. ferox to treat diseases and control parasites. The study also revealed that the choice of medicine (traditional or conventional) was influenced (P<0.05) by level of education and income. In the second phase of the research, a total of 600 Ross 308 day-old broilers, were randomly put in 6 treatment groups with 4 replicates, each having 25 birds. Fresh aqueous A. ferox leaf juice (ALJ) was administered in drinking water at a dosage of 20ml/litre to T1, T2 and T3 from day one to day 35, day one to day 14 and day 15 to day 28, respectively. Birds in T4 and T5 (positive controls) were treated with terramycin at the recommended dosage of 14g/litre of drinking water from day one to day 6 and from day 15 to 20, respectively; and birds in T6 (negative control) received distilled water from day 1 to 35. Feed Intake (FI), average daily gain (ADG) and feed conversion ratio (FCR) were calculated for the 5 week trial. After slaughter, carcass characteristics particularly dressing percentage (DP) and relative organ weight (ROW) were calculated. Serum biochemistry was also determined. For meat quality, pH and color were recorded 45 minutes and 24 hours after slaughter from the breast muscle. Fatty acid profiling and oxidative stability were determined using meat samples from the breast and thigh muscles. The results for growth performance showed that thebirds which were given A. ferox for the first two weeks (T2) consumed significantly (P>0.05) more feed (189.4g) than those in the negative control (159.6g) at the beginning of the starter phase. Subsequently, their ADG recorded on day 7 (27.1g) and day 14 (43.1g) were significantly (P<0.05) higher than the negative control (22.8g and 36.2g, respectively). Significant treatment effects (P<0.05) for FCR were reported in the 4th week for the birds that received A. ferox throughout (T1: 3.5). Carcass characteristics were not significantly (P>0.05) affected by A. ferox inclusion in drinking water. The highest high density lipoprotein (HDL) values (2.78 mmol/L) were yielded in T2and T3 had the lowest values (0.61mmol/L) for low density lipoprotein (LDL). For physico-chemical properties, no significant effects (P>0.05) of treatment on pH, colour, cooking loss and tenderness were observed. However, the group treated with A.ferox throughout the production cycle, had the highest pH (6.2), lowest lightness (38.5), highest redness (4.1), highest tenderness (13.86N) and the lowest cooking loss (12.6%). Significant treatment effects (P<0.05) were observed on the composition of the PUFA eicosatrienoic acid (C20:3c8, 11, 14(n-6)) of the breast muscle which was significantly lower in the A. ferox treatment groups than the positive controls. For the thigh muscle, there were significant (P<0.05) treatment effects on composition of palmitoleic acid (C16:1c9) and g-linolenic acid (C18:3c6, 9, 12 (n-3)). No significant (P>0.05) effects were found on oxidative stability of both thigh and breast muscles. In conclusion, the wide use of A. ferox by communal chicken farmers showed its importance as a medicinal plant. Apart from it being an effective medicinal plant, A. ferox inclusion in drinking water results in improved FI, ADG, reduced in LDLC and better g-linolenic and palmitoleic acid composition in the meat.

Three experiments, two with pigs and one with Atlantic salmon, (Salmo salar) were carried out to investigate the effects of dietary supplementation with α-tocopheryl acetate (ATA) on quality of pig and salmon tissues. In Experiment 1, 32 pigs were individually fed either of two dietary fat sources: 0.5:0.5 w/w coconut oil/lard (59 g/kg finisher diet) or rapeseed oil (100 g/kg finisher diet) (as contained in full-fat rapeseed {FFR}), with or without supplementary ATA at 200 mg/kg diet. In Experiment 2, 24 pigs were individually fed either a diet which contained mixtures of vegetable oil (59 g/kg diet) (having a high level of palm oil) or rapeseed oil diet as in Experiment 1. The rapeseed oil diets were supplemented with 0, 200 and 500 mg ATA/kg diet. In Experiment 3, a commercial diet with high lipid content (290 g/kg diet) and 250 mg ATA/kg diet was supplemented with 0, 400 and 700 mg ATA/kg diet. Diets were fed to 54 salmon. Tissue samples were stored at 4°C and/or -20°C for different periods. Spectral data on tissue samples were collected with an NIRSystems 6500 scanning monochromator. Salmon and pig tissues, and pig muscle subcellular fractions (microsomal and mitochondrial) were analysed for fatty acid composition, α-tocopherol (AT) content and oxidative stability (by thiobarbituric acid test). In both pigs and salmon, muscle drip loss was measured, and the colour score and carotenoid content of salmon fillets were determined. Data presented in this study indicate that pig tissues respond positively to increased dietary supply of unsaturated fatty acids (UFA). Pig tissue UFA and n-3 fatty acid contents were increased, and n-6/n-3 fatty acid ratio was decreased by feeding diets containing FFR. There was only a slight influence of dietary fatty acids on fatty acid composition of the subcellular membranes. AT concentration was higher in the mitochondrial fraction than the microsomal fraction. The mitochondrial fraction lipids had a higher content of UFA than those of the mcirosomal fraction. Supplemental dietary ATA increased the AT content of both pig and salmon tissues.

Thesis (MA)--Stellenbosch University, 2004.
ENGLISH ABSTRACT: Meat processing industries in South Africa are faced with the challenge to produce a variety of white meats. This is due to the fact that consumers tend to consume less red meat and more chicken and pork that are perceived to be healthier due to the negative publicity surrounding red meat and health. The nutritional emphasis is on leaner carcasses and an increase in the consumption of polyunsaturated fatty acids while reducing the ratio of n-6:n-3 polyunsaturated fats in the diet. Another way in which this can be achieved is through introducing rabbit meat which has low fat, low cholesterol content and high protein content, while displaying a positive fatty acid profile. Carcass quality and meat quality in rabbits may to a large extent be affected by age of slaughter and type of breed. This study had a dual purpose. Firstly it aimed at quantifying the effects of breed and age on parameters pertaining to carcass quality and meat quality of commercial rabbits, namely California breed and hybrid (California x Dutch red). Secondly, to determine the differences between ethnic groups on their perceptions towards rabbit meat, thereby providing information on its marketing potential. To accomplish the first objective 50 rabbits from the two breeds were housed in individual cages, weighed on weekly basis and fed ad libitum. The rabbits were slaughtered at 9, 11, 13, 15 and 17 weeks of age (n=5 from each breed). For the second objective the perceptions of three ethnic groups on factors affecting consumers' choice of rabbit meat were determined through a structured questionnaire. The questionnaire was tested for validity beforehand. There was no significant difference between the two breeds regarding body weight, feed intake, carcass weight and drip loss. The California breed had a higher dressing percentage (53.7%) and meat yield (29.2%) compared to the hybrid (52.5% and 27.5% respectively). Age treatments showed a highly significant difference on all parameters investigated. Increasing the age proportionately increased the amount of fat, while the moisture content decreased. The California breed exhibited higher percentages of fat compared to the hybrid at all ages of treatment. California breed contained more phosphorus, magnesium and zinc as opposed to the hybrid, the only exception being copper, where the hybrid had higher concentrations. The total fatty acid (169.2 mg/100 g) of the California breed was higher than that of the hybrid (133.5 mg/100 g). As a result there were more saturated fatty acids (55.4 mg/100 g) and monounsaturated fatty acids (62.3 mg/100 g) in the California breed than in the hybrid (44.2 and 45.6 mg/100 g respectively). Both breeds had 67% unsaturated fatty acids. Although there was no significant difference between the P:S ratio of the two rabbit breeds, the values obtained were higher (+0.9) than the value of 0.7. This is an indication that the rabbit meat contains a P:S ratio that could be considered very desirable. The n-6:n-3 ratio for both breeds were high (11.6 for California and 12.7 for hybrid). The cholesterol and amino acid profile of the two breeds were not affected by the type of breed. The consumer survey indicated that 52% (n=158) of respondents had never eaten rabbit meat before due to reasons such as scarcity, lack of knowledge about the meat, associating rabbits with pets and cultural constraints. Nevertheless, 57% of these people were optimistic about eating rabbit meat. In addition, having eaten rabbit meat before seemed to contribute positively towards acceptance of rabbit meat. Generally, respondents preferred purchasing rabbit meat in portions as opposed to live or whole carcasses. Their decision to purchase rabbit meat was firstly driven by price, thereafter freshness, leanness and tenderness of meat. The respondents expect to buy rabbit meat at a price lower than that of chicken. Rabbit meat contained low sodium and high proportion polyunsaturated fatty acids-some of the most important food attributes required to maintain and improve health. However, most of the respondents in this study were not familiar with the positive attributes of rabbit meat and need to be taught the benefits of this product.
AFRIKAANSE OPSOMMING: In Suid Afrika is daar 'n uitdaging vir die vleisproduserende voedselindustrieë om 'n verskeidenheid witvleis te bemark. Dit word toegeskryf aan die feit dat verbruikers minder rooi vleis as hoender en vark eet wat as meer gesond beskou word weens die negatiewe publisiteit wat geassosieer word met rooivleis en gesondheid. Die voedingsfokus is op maerder karkasse, groter inname van polionversadigde vetsure, en 'n vermindering in die verhouding n-6:n-3 poli-onversadigde vetsure in die dieet. Een van die maniere waarop dit gedoen kan word, is die bekendstelling van konynvleis wat gekenmerk word deur lae vetinhoud, lae cholesterolinhoud en 'n hoë proteïninhoud, en 'n positiewe vetsuurprofiel. Karkas- en vleiskwaliteit van konyne word tot 'n groot mate geaffekteer deur ouderdom van slagting en die ras. Hierdie studie het 'n tweeledige doel. Eerstens mik dit na die kwantifisering van die effek van ras en ouderdom op die parameters wat met karkas- en vleiskwaliteit van die Kaliforniese ras en die kruisgeteëlde ras (Kaliforniese X Hollandse rooi) verband hou. Tweedens, om die verskille in etniese groepe vas te stel met betrekking tot hulle persepsies van die faktore wat hulle keuse van konynvleis beïnvloed, en op dié wyse inligting te verkry t.o.v die bemarkingspotensiaal daarvan. Om in die eerste doelwit te slaag is 50 konyne van die twee rasse in individuele hokke gehuisves, op 'n weeklikse basis geweeg en ad libitum gevoer. Die konyne was geslag op 9, 11, 13, 15 en 17 weke (n=5 vir elke ras). Vir die tweede doelwit, is die persepsies van drie etniese groepe oor die faktore wat die verbruikerskeuse van konynvleis kan bepaal, m.b.v. 'n gestruktureerde vraelys bepaal. Die vraelys is vooraf vir geldigheid evalueer. Daar was geen beduidende verskil tussen die twee rasse wat betref liggaamsmassa, voedselinname, karkasgewig en dripverlies nie. Die Kaliforniese ras het 'n hoër uitslag-persentasie (53.7%) en vleisopbrengs (29,2%) in vergelyking met die kruisgeteëlde ras (52.5% en 27.5% respektiewelik) gehad. Ouderdom het hoogsbeduidende verskille op al die parameters wat ondersoek was, getoon. Die toename in ouderdom was gepaardgaande met proporsionele toename in karkasvet en afname in vog. Die Kaliforniese ras het, by alle ouderdomsbehandelings, in vergelyking met die kruisgeteëlde ras, 'n hoër persentasie vet opgelewer. Die Kaliforniese ras het teenoor die kruisgeteëlde ras hoër fosfor, magnesium en sink bevat. Die uitsondering was koper waar die kruisgeteëlde ras 'n hoër waarde gehad het. Die totale vetsure vir die Kaliforniese ras (169.2 mg/100 g) was hoër as vir die kruisgeteëlde ras (133.5 mg/100 g). Om dié rede was daar in die Kaliforniese ras meer versadigde vetsure (55.4 mg/100 g) en monoonversadigde vetsure (62.3 mg/100 g) as vir die kruisgeteëlde ras (44.2 mg/100 g en 45.6 mg/100g onderskeidelik). Beide rasse het 67% onversadigde vetsure gehad. Hoewel daar geen beduidende verskille was in die polionversadigde:versadigde (P:V) verhouding nie, was die waardes hoër (+0.9) as die 0.7 wat aanbeveel word. Die n-6:n-3 verhouding vir beide rasse was hoog (11.6 vir die Kaliforniese ras en 12.7 vir die kruisgeteëlde ras). Die cholesterol- en die aminosuurprofiel was nie deur die ras beïnvloed nie. Die verbruikersnavorsing het getoon dat 52% (n=158) van die respondente om verskeie redes nog nie konynvleis geëet het nie, weens redes soos onverkrygbaarheid, gebrekkige kennis van die vleis, die assosiasie van konyne met troeteldiere en kulturele beperkinge. Desnieteenstaande is daar 57% van die respondente wat optimisties is oor die eet van konynvleis. Die eet van konynvleis by vorige geleenthede het bygedra tot die positiewe aanvaarding van konynvleis. Oor die algemeen het die respondente verkies om konynvleis in porsies te koop, in plaas van lewendig of heel karkasse. Die besluit om konynvleis te koop, is hoofsaaklik gedryf deur prys, daarna deur varsheid, maerheid en sagtheid van die vleis. Die respondente verwag dat die prys vir konynvleis laer sal wees as vir hoender. Konynvleis bevat lae natrium en 'n hoë verhouding poli-onversadigde vetsure - van die mees belangrike voedingeienskappe om gesondheid te handhaaf en te verbeter. Ongelukkig was meeste van die respondente in hierdie studie nie vertroud met die positiewe eienskappe van konynvleis nie, en moet hulle geleer word deur middel van omvattende bemarkingsaksies van die voordele van hierdie produk.