Onalenna‬ ‭Onneile‬‬ Molaletsi ‭


Consumer and Food Sciences


MSc Food Science

Heat inactivation and survival of Listeria monocytogenes during polony production and shelf life

Food safety is a critical component of food nutrition and security, particularly in developing countries where the socio-economic status of a majority of the population is poor. The incidence of foodborne illnesses in developing countries is a major concern, in 2009 the World Health Organisation (WHO) estimated a total of 800 000 deaths due to diarrheal diseases in children worldwide, of which 80% of the cases were in developing countries (Ortega David, 2017). South Africa has experienced its food safety challenges, particularly those due to food pathogens and pesticides and antibiotic residues in food (Boatemaa et al., 2019). The most recent food safety issue in South Africa is the listeriosis outbreak, which the WHO dubbed the world's largest outbreak (Allam et al., 2018, Boatemaa et al., 2019), and polony was found to be the culprit (Boatemaa et al., 2019, Olanya et al., 2019, Smith et al., 2019). Polony is a South African version of the commonly known bologna sausage. The product is cheap and easily accessible to most people hence the most consumed RTE meat product in the country (Boatemaa et al., 2019), with significant contribution to the country’s economy in both the domestic and export markets (Olanya et al., 2019).

Production and preservation of polony rely primarily on heat processing and refrigerated storage to slow down the growth of L. monocytogenes. The pathogen, however, is reported to have the ability to survive harsh processing and preservation conditions, due to its ability to sense and respond to the various stresses it come across (Boor, 2006, NicAogáin and O’Byrne, 2016). Isolation of L. monocytogenes in polony and polony processing environment and its implication on the outbreak called for a prompt response to strengthen the food safety measures in South Africa (Olanya et al., 2019, Smith et al., 2019). The measures include pre-emptive L. monocytogenes inactivation and detection to enhance control of the pathogen (Allam et al., 2018). The application of predictive microbiology models can also assist the South African polony industry in timely pathogen detection. The models can accurately predict the growth of L. monocytogenes in response to relevant stresses applicable to a specific food product, taking into account the intrinsic and extrinsic characteristics of food (Mejlholm and Dalgaard, 2015).

Application of predictive models can provide cost-effective substitutes for traditional microbiological testing, especially in South Africa, where end-product testing is the main food safety assurance practice. Assuring the effectiveness of the conventional polony processing method in inactivating L. monocytogenes strains, together with the application of predictive microbiology models in estimating the growth of the pathogen in polony will provide information that can aid in strengthening food safety management procedures in South Africa, and consequently help to prevent the incidence of listeriosis outbreaks.


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  • Primary supervisor: Prof EM Buys

Research Profiles

  • https://www.researchgate.net/profile/Onalenna-Molaletsi
  • http://linkedin.com/in/onalenna-molaletsi-77113117a
Published by Gertruida Erasmus

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