Masters Degrees (Food Science)

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The occurrence of fungi in the manufacturing of fruit-based baby food puree packaged in retort pouches
(Stellenbosch : Stellenbosch University, 2024-03) Kelfkens, Jesse; Gouws, Pieter; Sigge, Gunnar; Stellenbosch University. Faculty of Agrisciences. Dept. of Food Science.
ENGLISH ABSTRACT: The ability of fungi (yeasts and moulds) to spoil high-acid, fruit-based products is a pervasive issue in the fruit-processing sector, particularly when the product in question is to be consumed by infants and young children. Over the last decade, fugal research in the food industry has been extensive yet mostly focused on fungi associated with a single raw material or fruit juice. Additionally, prior research on fungal spoilage of processed fruit-based products in South Africa or packaged in retort pouches remains sparse. Hence, the purpose of this study was to investigate the possible sources of fungi contributing to the occurrences of spoilage of a pasteurised, high-acid, fruit and vegetable-based baby food packaged in retort pouches. This thesis separates the different fungi into the following categories Fungi (yeasts and moulds), heat sensitive moulds (HSM) and Heat Resistant Fungi (HRF). Each of the mentioned categories is dealt with in its own chapter. The succeeding chapter summaries will further outline the conducted research. The thesis opens by discussing the research question, its context, and motivation, followed by an extensive literature review and methodological framework development. The sampling approach and methodology are tested and refined through a pilot study. The analysis of general fungi, filamentous fungi (mould), and heat-resistant fungi during fruit processing and baby food manufacture is presented along with practical ideas for preventing fungi-spoiled baby food. Industry benefits from these insights are highlighted, potentially providing advantages to organisations dealing with comparable products. Limitations and concluding notes, including future research recommendations, flesh out the findings of the study, helping to improve food safety and procedures for production.
Evaluating antimicrobial resistance profiles, UV response, and curli production in Gram-negative river water isolates from the Cape Winelands
(Stellenbosch : Stellenbosch University, 2024-03) Kuster, Margot Ellen; Sigge, G. O.; Lamprecht, Corne ; Rip, Diane ; Stellenbosch University. Faculty of Agrisciences. Dept. of Food Science.
ENGLISH ABSTRACT: Resistance by pathogenic microorganisms to antimicrobial agents is rising, posing a threat to human health. Aquatic environments provide the ideal setting for the dissemination and acquisition of antibiotic resistance. Following contamination via irrigation water, fresh produce becomes an ideal vector for the spread of pathogenic and antibiotic resistant microorganisms. Globally, increased consumption of these often untreated foods raises the risk of foodborne illness and exposure to antibiotc residues. Water from certain rivers used for the irrigation of fresh produce in the Cape Winelands region has been identiﬁed as unsuitable for irrigation, with faecal coliform concentrations exceeding guidelines. Additionally, studies have identiﬁed antibiotic and multidrug resistant bacteria in these waters. Treatment of contaminated waters before irrigation is thus necessary. Ultraviolet (UV) irradiation has successfully inactivated pathogenic microorganisms, but its efficacy on antibiotic resistant bacteria varies. Litle is known about the impact of irradiation on the antibiotic resistance proﬁles of resistant bacteria, or how photoreactivation and dark repair inﬂuence these bacteria. Similarly, while surface adhesion and self-aggregation structures are thought to reduce eﬃcacy in UV treatment of waters, limited literature is available to substantiate these claims. This study, therefore, aimed to establish extensive antibiotic resistance profiles of bacterial river water isolates from certain rivers sites in the Cape Winelands region and to determine the impact of UV irradiation on the antibiotic resistance profiles of these river water isolates. It also aimed to identify the presence of curli (a surface adhesion structure) within isolates to understand whether these may influence UV treatment. Extended-spectrum beta-lactamase (ESBL)-producers isolated by Oosthuizen (2022) originating from the Mosselbank, Franschhoek, Plankenburg, Eerste, and Jonkershoek rivers, and isolates exhibiting UV resistance following a recovery period isolated by Jankowitz (In press) from two locations on the Berg river and one location on the Eerste river were investigated. Bacterial identiﬁcation testing revealed a prevalence of Escherichia coli in the rivers. Antibiotic susceptibility testing to 19 antibiotics revealed that ESBL-producers exhibited greater antibiotic resistances when compared to non-producers, and a link between ESBL- production and multidrug resistance (MDR) could be established. Resistances to ‘critically important’ and ‘highly important’ antimicrobials for human medicine, as classiﬁed by the WHO, were prevalent in both sets of isolates indicating potential misuse of these antimicrobials in the region. A subset of ESBL-producing E. coli with heightened antibiotic resistance (n=6), and non ESBL- producing E. coli with heightened antibiotic susceptibility which had previously exhibited UV resistance qualities (n=7) were further investigated. Isolates underwent an 80 mJ.cm⁻² low-pressure UV treatment followed by a recovery period, which yielded good log₁₀CFU.mL⁻¹ reductions (mean log₁₀CFU.mL⁻¹ reduction = 6.68). Survival following recovery was low, but results exhibited a trend of increased survival following light recovery when compared to dark recovery. Post-treatment enrichment was found to promote growth in isolates exhibiting low counts. UV irradiation at 80 mJ.cm⁻² had little impact on the antibiotic susceptibility profiles of the isolates, but changes in resistances to ‘critically’ and ‘highly’ important antimicrobials were seen. A high prevalence of curli fibre production was detected in the more antibiotic resistant ESBL-producing E. coli. Curli-producing isolates expressed curli at both 37°C and 26°C, a critical finding given the typical high summer temperatures and reliance on irrigation in the Cape Winelands region during the spring and summer seasons. Overall, the study conﬁrmed the presence of antibiotic and multidrug resistance in bacteria isolated from certain rivers used for irrigation of fresh produce in the Cape Winelands region. UV irradiation at 80 mJ.cm⁻² was found to be a feasible water treatment technique to reduce E. coli concentrations to within irrigation water guidelines. While recovery was low in the isolates after UV treatment, findings highlight the need to consider the potential for recovery during storage and distribution. The link identified between antibiotic resistance and curli production in E. coli is concerning as irrigation using waters containing curli- producers could result in a heightened risk of exposure of fresh produce consumers to antimicrobial resistant bacteria.
The incidence of Escherichia coli in dairy products from retail markets in the Stellenbosch region
(Stellenbosch : Stellenbosch University, 2024-03) Issel, Cheryl; Gouws, Pieter; Stellenbosch University. Faculty of Agrisciences. Dept. of Food Science.
ENGLISH ABSTRACT: Several foodborne outbreaks linked to Escherichia coli (E. coli) have been reported and documented internationally and the source of many of the outbreaks were milk and milk products. Milk from the mammary gland is normally sterile, however, it can contain microorganisms from various sources during production, processing and distribution. The purpose of this research project was to investigate the incidence of E. coli in some of the dairy products sold at retail markets in the Stellenbosch region and to identify any risk factors. A total of 83 samples were sourced and analysed to determine the microbial load and the presence of coliforms and incidence and presence of Escherichia coli in raw milk, pasteurised milk, fresh cream and plain yoghurt. Standard methods were used to determine the microbial load and presence of coliforms and E. coli in the products. The products were chosen according to predetermined criteria. Standard Plate Count was used to determine the microbial load and International Dairy Federation method 73A of 1985 was used for the coliforms and E. coli enumeration. Coliform and E. coli plates were examined under UV light after incubation and all fluorescent colonies were regarded as positive for E. coli. The incidence of E. coli was 50% in the raw milk samples (n=20) and absent in all other products (pasteurised milk, fresh cream and plain yoghurt). However, plain yoghurt was the only product that contained no coliforms or E. coli in any of the samples analysed. When evaluated according to the standards prescribed in the Foodstuffs, Cosmetics and Disinfectant’s Act, 1972 (Act No. 54 of 1972), published under Government Notice No. R.1555 of 21 November 1997, 85%, 25% and 47% of samples were non-compliant to coliform standards for raw milk, pasteurised milk and fresh cream respectively. The incidence of E. coli in milk and milk products can be attributed to several risk factors like animal health, housing and husbandry practices, cleaning of equipment, hygiene of personnel, cooling conditions and transport, processing and distribution conditions. The results indicate more emphasis should be placed on hygienic and cooling conditions during all stages of production, processing and distribution.
Evaluating near infrared spectroscopy as a rapid screening tool for microbiological safety of rooibos (Aspalathus linearis)
(Stellenbosch : Stellenbosch University, 2023-03) Smith, Anne; Williams, Paul James; Stellenbosch University. Faculty of Agrisciences. Dept. of Food Science.
ENGLISH ABSTRACT: Rooibos, or Aspalathus linearis, is a popular South African beverage, known worldwide for its wide array of health benefits. While rooibos is marketed as a health product, very limited information is available on the microbiological safety of rooibos. Microbiological testing methods currently available in the industry is time- consuming, costly and potentially inaccurate. Given rooibos’ known association with microbiological contaminants such as Salmonella, E. coli and coliforms, this study aimed to assess near infrared (NIR) spectroscopy as a feasible alternative for rapid screening of the microbiological safety of rooibos. Rooibos samples (n=30) were collected from the final stages of processing, to represent the samples used in industry for microbiological screening. Both control (n=15) and contaminated (n=15) samples from various regions and harvesting seasons were chosen to increase the variation within the sample set. All samples had known moisture contents (in the range of 8.8 % to 9.8 %) and microbiological profiles. All unsafe samples had only coliforms present as no samples containing E. coli or Salmonella could be obtained at the time of the study. Through principal component analysis (PCA), a distinctive separation emerged when plotting PC 1 (82.28%) against PC 4 (0.45%). This separation, observed in the direction of PC 4, suggested a significant distinction, between safe and unsafe samples. To investigate potential correlations with moisture content, samples were colour-coded accordingly. However, no discernible patterns related to moisture content emerged in the direction of PC 4. As a result, the conclusion was drawn that the observed separation along PC 4 was indicative of the presence of coliforms, serving as a marker for microbiological safety. The study demonstrated that employing NIR spectroscopy and partial least squares discriminant analysis (PLS-DA) enabled the development of a calibration and prediction model with 100% classification accuracy, sensitivity and specificity. With no instances of misclassification, this model emerges as a feasible option for use in industry. The study not only established the potential of NIR spectroscopy for microbiological safety screening, it also employed multivariate data analysis techniques. These included the examination of PC loadings and PLS-DA regression vectors, identifying critical wavelengths (1720 nm, 1930 nm and 2310 nm). These wavelengths, associated with moisture content and CH stretching, played a crucial role in discriminating between safe and unsafe samples. The presence of coliforms were inferred from these wavelengths. While addressing the current gap in microbiological safety assessments of rooibos, this research shows the potential of using NIR spectroscopy as a rapid and accurate screening tool for rooibos classification. The findings pave the way for improved food safety control practices and highlight the need for future research in the application of spectroscopic techniques to ensure the safety of rooibos.
Assessment of access to food by households in Epworth (Ward 3) Harare, Zimbabwe
(Stellenbosch : Stellenbosch University, 2024-03) Phiri, Alice; Boatemaa Kushitor, Sandra; Sigge, Gunnar; Stellenbosch University. Faculty of Agrisciences. Dept. of Food Science.
ENGLISH ABSTRACT: Urban food insecurity is on the rise globally, particularly in the global south which is experiencing a surge in urbanization. High poverty levels, high levels of unemployment, volatile exchange rates, inflation, rising food prices, and generally high cost of living are some of the drivers of urban food insecurity in sub-Saharan Africa. Zimbabwe has gone through decades of macro-economic and political instability increasing the vulnerability of urban and peri-urban dwellers to food insecurity. This study assessed how households in Epworth, Ward 3 access food and the degree of coping when households do not have enough food or income to purchase food. The study sought to determine the level of food insecurity in Epworth Ward 3, the levels of income of households in Epworth, their sources of income and food, the percentage of income they spend on food and the degree of coping employed by households. To answer these questions quantitative research based on a case study approach was carried out in Epworth Ward 3 in which 200 households were sampled using a random sampling technique. A questionnaire that adopted the FANTA questions (Coates et al., 2007) was used to capture the Household Food Access Insecurity Score (HFIAS), Household Dietary Diversity Score (HDDS), Food Consumption Score (FCS), and the Reduced Coping Strategy Index (rCSI) indicators of food security. Findings from the research showed that more than half of the sampled households were moderately and severely food insecure. A greater number of households in Epworth Ward 3 consumed 2 meals per day. There is varied dietary diversity among the sampled households however, there is a sizeable population that consumes poor diets. Most households in Epworth rely on market purchases as their source of food. Total monthly incomes of the sampled households are very low and households spent a greater proportion of their incomes on food. Results showed that households with low monthly incomes were more food insecure. The study also showed that the more food insecure the higher the degree of coping. Overall food insecurity in Epworth Ward 3 is still very high. The research recommended continuous monitoring of the food security situation in Epworth with evolving macroeconomic conditions in Zimbabwe to continuously have a clear picture of the food insecurity in the area. This will inform the local board and decision-makers to tailor-make interventions that address the needs of different households in Epworth. Since most households rely on street and mobile vendors as sources of food there is a need to monitor and assess the safety and hygiene practices. The research recommends school feeding programs to increase the number of meals consumed by school-going children thereby improving their food and nutrition security situation. The researcher also recommends the government to introduce social safety net programs in Epworth as households are in precarious food security situation.

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