Doctoral Degrees (Microbial, Biochemical and Food Biotechnology)

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Browsing Doctoral Degrees (Microbial, Biochemical and Food Biotechnology) by Advisor "Hugo, A."

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    The effect of dietary conjugated linoleic acid supplementation on production efficiency and meat quality of pigs
    (University of the Free State, 2014-01) Ferreira, Jacobus Philip; Hugo, A.; Strydom, P. E.; Kock, J. L. F.; Kanengoni, A.
    The objectives of this study were to determine the effects of a commercial dietary CLA feed supplement on the production and meat quality parameters of pigs under commercial production conditions. It included the study of the chemical and sensory stability of processed meat products manufactured from the meat of such animals. One hundred and forty four Landrace x Large White crossbred pigs, weighing ± 30 kg, were randomly divided into two groups of seventy two pigs each, that were assigned to one of two dietary treatments. Diets consisted of a control diet supplemented with 1% SFO and the experimental diet where 0.5% SFO was replaced with 0.5% CLA. Each dietary group was further divided into three gender groups (boars, barrows and gilts) that consisted of twenty four pigs each. Each gender group was further divided into two slaughter weight groups (70 kg and 90 kg) consisting of twelve pigs each. Pigs were fed until the average live weight of the pigs was ± 70 kg for the porkers and ± 90 kg for the baconers. Growth performance (weight increase, ADG and FCR) and carcass characteristics (warm and cold carcass mass, dressing percentage, carcass length, shoulder and buttock circumference, pH, backfat thickness, eye muscle thickness and LMC) were assessed. Animals receiving the CLA diet had improved FCR and carcasses with thinner backfat and higher LMC, compared to animals on the SFO diets. This resulted in a higher frequency of P and O classification of carcasses from CLA supplemented pigs. Backfat, belly fat and M. longissimus thoracis quality of the dietary treatment and slaughter weight groups were compared. Baconers had improved technological properties compared to porkers. Dietary CLA supplementation resulted in improved technological properties of backfat and belly fat, demonstrated by decreased IV; RI; DBI; UFA; MUFA; PUFA; MUFA/SFA ratio; PUFA/SFA ratio; 9 desaturase index; C16:1 + C18:1/C16:0 + C18:0 ratio and increased C18:0; cis-9, trans-11; trans-10, cis-12; SFA; AI; C16:0 + C18 and ratios of C18:0/C18:2; C18:2/C18:1; C16:0/C18:2. M. longissimus thoracis from CLA supplemented pigs had higher a*-values, drip loss and WHC. Dietary CLA supplementation resulted in a decrease of health and nutritional properties of M. longissimus thoracis, demonstrated by increased SFA content and AI, while UFA, MUFA, PUFA, n-6, n-3 and ratios of MUFA/SFA and PUFA/SFA decreased. Technological and health properties were inversely related. The decreased health properties must be weighed against the numerous health benefits, ranging from improved immune function to prevention of cancer that can be attributed to CLA supplementation. Conjugated linoleic acid isomers were deposited into the neutral- and glycolipid fraction of subcutaneous adipose tissue and into the phospholipid fraction of IMF. Processed products (patties, bacon and salami) were manufactured from meat from the experimental treatment groups. The chemical stability and sensory properties of fresh meat and processed products manufactured from the experimental treatment groups were compared. Conjugated linoleic acid also demonstrated antioxidant properties in animal feed. Sensory analysis indicated the small effect of dietary CLA supplementation on the sensory properties of fresh and processed pork products. In the case of fresh pork chops and pork patties, dietary CLA supplementation had a stabilizing effect on the a*-value of the products. The lipid stability of pork patties was improved by dietary CLA supplementation as indicated by TBARS values. Salami from the CLA groups was firmer. That could be ascribed to the fat hardening effect of CLA. Pork and pork products enriched with CLA can be considered functional foods and even “nutraceuticals” with positive effects on human health. South African pig producers may therefore consider marketing CLA enriched pork products as a health food. The potential advantages and the premium that can be earned on such meat has to be balanced against the reality of increased feed cost.
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    The effect of dietary conjugated linoleic acid supplementation on the physicochemical, nutritional and sensory qualities of pork
    (University of the Free State, 2014-05-27) Bothma, Carina; Hugo, A.; De Kock, H. L.
    English: Forty eight gilts were fed one of four dietary treatments containing 0, 0.25, 0.5 and 1% CLA, until their weight reached 95 kg and were then slaughtered. There were a lack of significant differences in pig performance and growth traits (weight increase, ADG, ADFI, FCR), and slaughter characteristics (SLW, hot carcass weight, cold carcass weight, dressing percentage, BFT, MT and LMC). There were no change in M.longissimus thoracis area, drip loss, WHC, pH45 and pH 24, while L*-and b* values decreased with increased dietary CLA. Colour a*-values and SI also did not differ between the four treatments. For the BF, IVs decreased with increased dietary CLA, while RI, colour a* and SI values remained unchanged, and colour b* values and hardness increased. Conjugated linoleic acid supplementation resulted in improved technological quality of subcutaneous fat, demonstrated by reduced IVs, unchanged RI and extractable fat content, and increased FFDM. With increase in CLA supplementation, C18:0, cis 9, trans 11, trans 10, cis 12, UFA, SFA, n-6/n-3, PUFA/SFA, dienoic acid, C16:0+C18:0, C16:0/C18:2, C16:1+C18:1c9/C16:0+C18:0 and C18:0/C:18:2 increased, C18:1c9/C18:0, MUFA, PUFA, MUFA/SFA, n-3, PI, trienoic, tetraenoic, penta + hexaenoic acid and DBI decreased, while n-6 remained unchanged. There was a tendency for sampling positions on the dorsal (neck, BF, chuck) and lateral (rib area) sides of the carcass to have higher CLA content. Differential scanning calorimetry of subcutaneous fat showed the presence of β’-crystals in fat from 0.25 and 0.5% CLA- fed pigs and β-crystals in fat from 1% CLA-fed pigs. For IMF samples, increased dietary CLA led to no change in IV, C18:0, C18:1t9, C18:1c7, C18:3n-3, PUFA/SFA, tetraenoic acid, C16:0/C18:2 and C18:0/C18:2 contents, while C16:1c9, cis- 9, trans-11, trans-10, cis-12, C22:5, C22:6, SFA, AI, PI, n-3, n-6/n-3, PUFA, n-6, dienoic acid, trienoic acid, penta- + hexaenoic acid, C16:0+C18:0 and C16:1+C18:1c9/C16:0+C18:0 contents increased and C18:1c9, C20:1c11, C18:1c9/C18:0, C18:2, C18:3n-6, C20:3n-3, C20:2, C20:4, C20:5, MUFA, UFA, MUFA/SFA and AI contents decreased. Most CLA was deposited on the lateral sides of the carcass, namely the M.triceps brachi. M.supra spinatus showed an atypical FA composition. Descriptive sensory analysis was performed on oven-broiled pork chops and fat samples by a trained panel. The control was rated most tender, confirming the results from the physical texture analysis. The control also had least resistance for first bite, with the 0.5% CLA treatment having most resistance. The 0.5% CLA treatment had a chemical aroma for the fat. The accelerated oxidation test indicated that BF from the control did not become rancid faster than BF from the three CLA treatments. Refrigerated display of pork chops for 8 days resulted in increased L*and b* values for the CLA treatments, unchanged TBARS values, while SI decreased. After frozen storage for 3 months, TBARS values remained unchanged for pork chops from the different dietary treatments. After 6 months of frozen storage, TBARS values decreased for pork chops from CLA supplemented pigs. After eight and 16 weeks of frozen storage, PVs for frozen patties decreased for the 0.5 and 1% CLA treatments. Differences in TBARS values became evident after eight weeks for the frozen patties, compared to sixth months for frozen pork chops. The TBARS values for the frozen chops were lower than the frozen patties. At the end of the ripening period, PVs for salamis from the 0.5 and 1% CLA treatments decreased, along with TBARS values. Belly fat from the CLA treatments was firmer than the control. No significant differences were observed between the four bacon treatments for either PV or TBARS values over the course of the six week refrigerated storage. According to the consumer panel, the control bacon was preferred to the 0.25% CLA bacon.
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    The effect of sodium reduction on the chemical, microbial and sensory quality of prominent South African processed meat products
    (University of the Free State, 2016-08) Cluff, MacDonald; Hugo, A.; Hugo, C. J.
    English: In light of the recent South African regulations limiting the sodium content of processed meat products, the latest draft of these regulations were used to establish to what extent commercial processed meat products deviated from these limits and required reformulation, two and a half years in advance of the first reduction limits coming into effect. Almost 60% of product labels already included information on sodium content almost three years before the applicable labelling regulations came into effect. Surveying nationally and regionally available products allowed for the identification of the five largest product classes. A comparison between labelled and determined Na content revealed that processors tended to overestimate Na content as a precautionary measure. A generous tolerance of 20% for underestimating the Na content, as stated in the labelling regulations draft, showed that only a small number of products would at the time, have exceeded the futuredated regulatory limits. Bacon, polony and pork bangers, representing the three most populous classes were used to evaluate the efficacy of the two-part regulatory limits as intermediate added NaCl levels without replacers or alterations in processing. Water activity, pH and moisture content were inconsistently affected with no definite links to deviations in dependent parameters such as microbial stability. Microbial and oxidative stability and sensory quality results were encouraging. Current processing techniques and ingredients other than NaCl maintained quality and stability. Changes in bacon and banger colour were found, although subjective evaluation is needed to grasp the implications. Polony texture was deemed acceptable, both quantitatively and qualitatively. Total Na levels better matching the regulatory limits may further limit the minor deviations in quality and stability. The relative success of using only 1% NaCl (w/w) in the pork bangers prompted the use of various compounds, either alone or in combination, to address the gaps in functionality of the 1% NaCl removed from the original formulation. Potassium chloride (1% w/w), K-gluconate (1% w/w), KCl (0.8% w/w) with YE (1% w/w) and lastly, KCl (0.8% w/w) with K-lactate (0.2% w/w) were compared to 1% NaCl and 2% NaCl controls. Treatments containing KCl had improved cooking losses over that of the controls. The use of K-containing compounds increased the K-content in addition to reducing Na-content. Basic chemical parameters were similar to that of the 2% NaCl control with only water activity being more similar to that of the 1% NaCl control. These replacers did not improve lipid oxidative stability and the use of YE actively deteriorated lipid oxidative stability. Colour was the most affected multi-component parameter and consumers had less favourable hedonic responses towards the use of K-gluconate. Partial replacement with 1% KCl was the most suitable solution when additional factors such as price-point, similarity to NaCl, and ease-of-use were taken into account. Lastly, the efficacy of the reduction and/or partial replacement of NaCl against the growth and survival of E. coli and S. aureus inoculated into banger batters were monitored. No effects on E. coli were observed beyond the bacteriostatic effect of sub-optimal temperatures (4 °C and 10°C) and the anti-microbial effects of the other additives in the formulations. At reduced NaCl levels, S. aureus was unable to grow and survival rate ultimately decreased. Partial replacement led to limited growth although survival rates eventually decreased. Survival rates were highest at 1% NaCl, 1% KCl and 0.2% K-lactate. Sub-optimal temperatures and other anti-microbial effects overrode that of partial NaCl replacement. Beyond the initial inoculation levels, reduction and/or partial replacement of NaCl did not increase the food safety risk of these bacterial species. This research showed that conformation with the regulatory limits warrants a back-to-basics strategy using multiple approaches that deliver better results when these approaches are linked to one another.