Browsing by Author "Groenewald, Jadri"

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    The effect of steam pasteurisation and gamma-irradiation on the microbial profile of Aspalathus linearis (Rooibos) tea and the investigation of the native lactic acid bacteria profile
    (Stellenbosch : Stellenbosch University, 2023-12) Groenewald, Jadri; Gouws, Pieter Andries; Kirby-McCullough, B.; Stellenbosch University. Faculty of Agrisciences. Dept. of Food Science.
    ENGLISH ABSTRACT: Due to the increase in popularity of rooibos amongst local as well as international consumers, as reported by the South African Rooibos Council (SARC), rooibos in recognised as an economically valuable crop leading to an increase in commercial farming (Koch et al., 2012, Joubert et al., 2011). The increase in commercial farming requires the establishment of a commercial process that not only ensures consistent quality of the final product but ensures adherence to both local and international regulations regarding the microbiological safety of herbal foodstuffs. Research in needed to not only determine the quality attributes associated with the products unique polyphenolic profile but to determine processing parameters that allow for standardised production processes with measurable quality control points as well as critical control parameters, thus ensuring a consistent quality as well as safe product for the consumer. As such this study aimed to assess the efficacy of the currently employed steam pasteurisation process as well as an alternate cold pasteurisation process, namely gamma irradiation, at reducing the microbial load of the final product. It was found that the steam pasteurisation process ensured a greater than 3 log reduction of total aerobic microorganism density as well as coliform density, however the organisms remained present at a detectable level. However, Salmonella spp. were detected on 3% of the pasteurised rooibos samples thus indicating that the currently employed microbial reduction step, namely steam pasteurisation, is not able to reduce the Salmonella CFU/g to not detected in 25g as required by international food safety microbial guidelines. In comparison gamma irradiation at a dose rate of equal to or above 7.5 kGy is was found to reduce the microbial load of fermented rooibos so as to adhere to both local and international regulations regarding the microbial contamination of herbal foodstuffs. The results indicate that gamma irradiation at a dose rate of 7.5 kGy is a viable option as an alternative to the current industry standard of steam pasteurisation. Furthermore, gamma irradiation was shown to have the ability to reduce the anaerobic endospore former density to undetectable levels, as compared to steam pasteurisation which only achieved a 0.01 log reduction, thus ensuring a safer product for the consumer as compared to a steam pasteurised rooibos product. The second aim of this study was to determine whether dried fermented rooibos could serve as a matrix for the isolation of lactic acid bacteria. The results indicated that fermented rooibos could serve as an isolation matrix for lactic acid bacteria as the following species were isolated though through culture dependent methods; Lactobacillus, Pediococcus, and Weissella. However, it remains important that the microbiome of rooibos tea is explored as a novel niche for the isolation of robust lactobacterial strains that can be applied in the food processing industry.