The effect of microbial and plant extract preservatives on the chemical, microbial and sensory quality of a traditional fresh South African sausage
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Date
2023
Authors
Freitag, Alicia
Journal Title
Journal ISSN
Volume Title
Publisher
University of the Free State
Abstract
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.
Description
Thesis (Ph.D.(Food Science))--University of the Free State, 2023
Keywords
sulphur dioxide replacement, boerewors, plant preservatives, protective cultures, shelf-life, microbial communities, SO₂ replacement, natural preservatives, escherichia coli, staphylococcus aureus, growth and survival, plant extracts