Masters Degrees (Sustainable Food Systems and Development)
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Item Open Access Acceptance, attitudes and nutritional content of novel nixtamalized maize products developed for the South African consumer(University of the Free State, 2023) Colbert, Taylon Anthony; Du Toit, Alba; Bothma, Carina; van Niekerk, Johan; Swanepoel, Jan WillemSouth Africa is well-known for its good quality maize that serves as a staple crop for over 80% of the country’s population. Additionally, South Africa is also Africa’s top maize producer. However, maize provides an unbalanced supply of essential nutrients, such as the essential amino acids lysine and tryptophan. Moreover, the water-soluble vitamin B₃ is biologically unavailable to humans. Therefore, long-term consumption of maize-based diets, deficient in these nutrients, can result in pellagra, a disease manifested by the characteristic symptom dermatitis, on sun-exposed skin. The process of nixtamalization improves the nutritional, textural and sensory quality, and the physicochemical properties of maize products. Nixtamalization is the traditional process of preparing maize in Mexico. It involves cooking and soaking maize kernels in an alkaline solution, typically calcium hydroxide or slaked lime. The process allows bound nutrients to be more readily available for absorption, improves flavour and texture, as well as digestion. This study was divided into three essential phases: (I) the development of consumer-acceptable novel nixtamalized maize products; (II) the determination of consumer attitudes, knowledge and awareness towards nixtamalization and nixtamalized maize products, through the administration of a questionnaire; and (III) the analysis of the nutritional content of a novel consumer accepted nixtamalized maize product. The first phase aimed to explore South African consumers' acceptance of nixtamalization and novel nixtamalized maize products. Three nixtamalized maize products were developed: a vegetarian patty; a vegetarian nugget; and a maize chip. To evaluate the consumers' sensory acceptance of various attributes, including taste, aroma, texture, and appearance, the study employed the Just-About-Right (JAR) scales and a 9-point hedonic scale. Among the three products evaluated, the maize chip received the most acceptable JAR results, although improvements were required for its appearance attribute. Furthermore, correlation and penalty analysis revealed that appearance and taste played significant roles in the acceptance of nixtamalized maize products, among South African consumers. Consequently, the chips were flavoured with seasonings to improve taste and appearance, with different flavours, such as chutney and tomato. Notably, the chutney-flavoured maize chip achieved an acceptance rate of >70.0% for all four attributes, rendering it “just-about-right”. The study's second phase involved determining consumers’ attitudes toward nixtamalization and nixtamalized maize products. The data was collected online, using an Evasys© questionnaire, which was anonymously completed by respondents, during the sensory tasting of the maize chips. Quantitative analysis concluded that most respondents were open to nixtamalization as a new processing technique and to newly developed maize products produced, through nixtamalization. Specifically, respondents indicated that the safety aspect of nixtamalization played a crucial role in their willingness to consume nixtamalized maize, in the future. Moreover, the results indicated that the respondents were willing to incorporate nixtamalized products into their future consumption, and recommend them to friends and family. After achieving consumer acceptance, the third phase of the study focused on conducting nutritional analysis of the novel nixtamalized maize chip. The analysis revealed several noteworthy findings. The chips exhibited a high energy content of 2303 kJ/100 g and protein content of 6.64 g/100 g. Compared to two commercial chips, the nixtamalized maize chip displayed a higher insoluble fibre content of 15.87 g/100 g of NDF and 1.32 g/100 g of ADF. Additionally, the sodium content of the maize chip (706.67 mg/100 g), fell within the permissible limit set out by South African salt legislation (<800 mg/100 g), for savoury snack foods. Moreover, the chips demonstrated favourable potassium, calcium, phosphorus, and magnesium levels. The higher fat content of 23.72 g/100 g in the chips was attributed to the deep-frying process, used during preparation.Item Open Access Evaluation of rejected wet carcass syndrome lamb meat for human or animal consumption(University of the Free State, 2023) Hatting, Melissa; Hugo, A.; Hugo, C. J.Wet carcass syndrome (WCS) is a condition found among sheep and is characterised by a ‘wet’ appearance of the subsurface meat at slaughtering. These carcasses are considered unfit for further use, resulting in financial loss to farmers and the industry as a whole. No preventions or cause have been determined for this syndrome, although WCS seems to be associated with winter/drought conditions. The current study compared twenty WCS carcasses to twenty unaffected normal carcasses to determine the quality and safety of the affected meat. Parameters tested included fat thickness, water holding capacity, colour, proximate analysis, fatty acid composition, water activity, pH and microbial load. A shelf-life study was performed on two products, i.e., lamb chops for human consumption and pet mince for the pet food industry. From morpho-physical examinations, WCS carcasses had measurements with significantly higher cold mass, external length, shoulder and buttock circumference than the normal carcasses. No significant differences were, however, found in the fatness and conformation code, showing that WCS-affected carcasses were physically larger, but retained the same level of fat around the outside of the carcass. Measurements taken between the 12ᵗʰ and 13ᵗʰ rib, showed normal carcasses had significantly higher fat thickness (45 mm and 110 mm), while WCS carcasses had significantly higher eye muscle width, depth, area and perimeter. The pH, temperature, water activity and water holding capacity had no significant differences. Proximate analysis included dry matter, moisture, protein, fat, organic matter and ash. All of these parameters showed higher levels in the normal vs WCS carcasses, except for moisture content which was higher in WCS vs normal carcasses. Nine of the fatty acids showed significant differences, where all but one, arachidic acid, had higher levels in the WCS, than in normal carcasses. From surface swabs, there were no differences in the number of microbes recovered from the surface of the WCS carcasses versus normal carcasses. Two products were formulated, lamb chops for human consumption and pet mince for the pet food industry. A shelf-life study (microbial load, colour and pH) determined the quality over a period of six days for lamb chops and 10 days for pet mince. The microbial load and pH on both products showed no significant differences between the WCS and normal carcasses, suggesting that WCS meat had the same microbial quality and was just as safe as that from a normal carcass. The colour analysis of the lamb chops showed no differences in the lightness nor the redness, although there was a difference in the blue/yellow colour on day 0, implying a greenish tint involved with WCS. This phenomenon, however, was only seen on day 0 and not throughout the 6-day experimental period. The study confirmed the safety of WCS meat for both human and animal consumption, although the wet surface appearance, soft texture and loose subcutaneous fat, is expected to still deter consumers from purchasing such meat. Processing of WCS meat into products like pet mince, will support new commercial ventures and lessen the financial impact of the condition on the livestock industry.Item Open Access The evaluation of plant extracts as natural preservatives on the chemical, microbial and sensory quality of boerewors(University of the Free State, 2023) Burger, Ané; Hugo, C. J.; Hugo, A.Nowadays, consumers prefer the use of natural preservatives over chemical preservatives. Boerewors, a typical South African fresh sausage, is usually preserved with sulphur dioxide (SO2), which is associated with negative health effects in humans. When partly replacing a preservative with another preservative, it is essential to maintain the same product quality and safety. The aim of this study was, therefore, to investigate the effect of plant extracts as natural preservatives on the chemical, microbial and sensory quality of Boerewors. Extracts of green Rooibos, honeybush and Rooibos consist of many beneficial uses, as they all provide antioxidant and antimicrobial activity in food products. The concentrations of use of each preservative should first be determined before it can be included in a food model. In the first part of the study, three concentrations of each of the three plant extracts were evaluated in vitro, using the disc diffusion assay, for microbial activity against five strains each of 𝘌𝘴𝘤𝘩𝘦𝘳𝘪𝘤𝘩𝘪𝘢 𝘤𝘰𝘭𝘪 and 𝘚𝘵𝘢𝘱𝘩𝘺𝘭𝘰𝘤𝘰𝘤𝘤𝘶𝘴 𝘢𝘶𝘳𝘦𝘶𝘴. The plant extracts with the most promising inhibition zones, were 0.25% Rooibos (R025), 0.50% honeybush (H050) and 2% green Rooibos (GR2). The GR2 showed the best inhibitory effect against both bacteria. In the second part of this study, R025, H050, GR2 and combinations of each with low SO₂ (S100 = 100 mg/kg SO₂) were evaluated as preservatives in eight Boerewors models over a period of 6 days at 4 ºC. The treatments included a negative control (NC), which had 0% preservatives and a positive control (S450 = 450 mg/kg SO₂). Physico-chemical analysis was conducted in terms of pH, water activity and lipid stability at 4 oC on days 1, 3 and 6. Lipid stability, measured by thiobarbituric acid reactive substances (TBARS), were also analysed after 90 days of storage at -18 ºC. Microbial analysis in terms of total bacterial count (TBC), Gram-positive bacteria (lactic acid bacteria and 𝘚𝘵𝘢𝘱𝘩𝘺𝘭𝘰𝘤𝘰𝘤𝘤𝘶𝘴 𝘢𝘶𝘳𝘦𝘶𝘴), Gram-negative bacteria (𝘌𝘴𝘤𝘩𝘦𝘳𝘪𝘤𝘩𝘪𝘢 𝘤𝘰𝘭𝘪), 𝘌𝘯𝘵𝘦𝘳𝘰𝘣𝘢𝘤𝘵𝘦𝘳𝘪𝘢𝘤𝘦𝘢𝘦, coliforms, yeasts and moulds were performed. The sensory quality of these treatments in terms of colour stability, the evaluation of sensory attributes (colour, taste, texture, and overall acceptability) by a sensory panel, as well as thaw-, cooking- and total losses, were analysed. No significant differences in the pH, water activity and TBARS values of the eight treatments were observed. The H050 + S100 showed the best inhibition against 𝘚𝘵𝘢𝘱𝘩𝘺𝘭𝘰𝘤𝘰𝘤𝘤𝘶𝘴 𝘢𝘶𝘳𝘦𝘶𝘴 and the total bacterial count in the Boerewors. Lactic acid bacteria and 𝘚𝘵𝘢𝘱𝘩𝘺𝘭𝘰𝘤𝘰𝘤𝘤𝘶𝘴 𝘢𝘶𝘳𝘦𝘶𝘴 were inhibited more effectively by S450 and the plant extract combinations with S100 near the end of shelf-life (day 6). The GR2 + S100 treatment had the best inhibition against the mould counts over the 6-day storage period at 4 ºC. In terms of CIE colour stability, S450 was the best in preserving the colour of Boerewors. The H050 and R025 treatments had the best colour among the treatments when evaluated by the sensory panel. The GR2 and GR2 + S100 treatments had significantly higher losses during thawing and cooking. In this research, partial replacement of SO₂ with plant extracts such as honeybush and Rooibos have been shown to be possible.