Sustainable Food Systems and Development
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Browsing Sustainable Food Systems and Development by Author "Hugo, A."
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Item Open Access The effect of microbial and plant extract preservatives on the chemical, microbial and sensory quality of a traditional fresh South African sausage(University of the Free State, 2023) Freitag, Alicia; Hugo, C. J.; Hugo, A.; van der Merwe, S.; Cluff, M.The purpose of this study was to determine if natural preservatives in Boerewors had an effect on the aᵥᵥ, pH, and moisture content; lipid oxidative, microbial and colour stability; and sensory quality. Sulphur dioxide inclusion at 0.035% (positive control), formulation with no preservatives (negative control), protective cultures; Pediococcus acidilactici (PrC1) and Lactobacillus curvatus (PrC2), and plant extract blends; rosemary extract and acerola oil (KD1) and rosemary extract, buffered vinegar, and acerola powder (KD2), were evaluated. The goal was to best match the quality characteristics of the positive control, while complying to the consumer demands for natural ingredients. The use of KD2 increased the pH on days 0 and 6, while the aᵥᵥ of were only affected on day 0, with PrC1 having the highest aᵥᵥ and KD1 the lowest. Both plant extract preservatives increased the lipid oxidative stability more than any other treatment, including the positive control. The microbial stability results were inconclusive due to the protective cultures which increased the total bacteria count. The pathogens, coliform and Enterobacteriaceae counts were analysed, but there were no significant differences between the treatments. KD1 maintained the highest lightness colour score and lowest TBC at the same level as the positive control but increased the yellowness score. The treatments had no effect on the sensory evaluation. The use of plant preservatives as the best candidates for SO₂ replacement were confirmed for use in Boerewors. The replacement of SO₂, with natural preservatives, can affect the product safety and shelflife of fresh meat products, such as Boerewors. The effect of the replacement on the microbial communities of Boerewors have not yet been investigated. Biolog™ Ecoplate™ have been used to physiologically profile bacterial communities from different preservative treated Boerewors samples. The Boerewors were sampled on day 0 and incubated at 25 °C, in an OmniLog® system, for 72.5 h. The growth and reaction of the microbial communities to the 31 carbon compounds were measured, based on the production of formazan. The results were statistically analysed, using two methods: 1) AWCD and Shannon indices, and 2) applying the Gompertz function to analyse growth parameters. The results of the first approach showed that KD1 had the lowest growth rate and a similar microbial diversity as the PC, while the NC had the highest overall growth and diversity. The results of the second approach showed that PrC1 had a much later midpoint of growth than the other treatments, while the microbial community in KD2 had the least explosive growth of all the treatments. Overall, a reduction in microbial functional diversity and explosiveness of growth was noted in Boerewors with added preservatives. In terms of community-level physiological profiling, SO₂ replacement can, therefore, affect the microbial quality and safety of Boerewors in mostly positive ways. In this study, SO₂ replacement with plant extract preservatives containing rosemary and acerola extract (KD1) and rosemary and acerola extract with buffered vinegar (KD2), were evaluated for effects on the growth and survival of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) reference strains. The bacterial strains were inoculated separately into Boerewors batters that were stored at 4 °C for up to 6 days. The purpose of this study was to determine if these potential pathogens could use natural preservatives to their advantage in Boerewors. The inoculated E. coli struggled to survive both of the natural preservatives, especially KD1, without a significant difference to the PC. Survival decreased substantially from day 0 to 6, with the low storage temperature having a big influence on the counts. The inoculated S. aureus decreased from day 0 to 6, but the natural preservatives did not affect the counts as much as the SO₂, except on the last day of storage. For the most part, natural preservatives and an ideal storage temperature exhibited antimicrobial potential.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.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.