Bacterial dynamics and the prevalence of foodborne pathogens associated with the avocado fruit, Persea Americana Mill. in a food processing facility

Avocadoes, Persea americana Mill., are considered a superfood being nutrient dense and containing 20 vitamins, minerals, fibre, and phytonutrients. The popular fruit is produced in many countries around the world and demand far outstrip production. South Africa is one of the leading producers and exporters to mainly the European Union. In South Africa, the fruit is patricianly favoured in fresh ready-to-eat salads and sandwiches making safety a priority for any food processing plant. Currently, the fresh produce industry in South Africa is not regulated in terms of have a specific microbial standard for ready-to-eat food leaving it up to the food industry to ensure quality and safety at the point-of- sale. Washing steps at processing plants must thus demonstrate consistent product quality and safety. The aim of this study was therefore to assess the bacterial microflora of avocado fruit before or after washing over an extended period of time and assess the potential presence of foodborne pathogens. The objectives of this study was to detect, enumerate and characterise total bacterial counts, assess the presence of faecal pollutant indicator organisms, presence of foodborne pathogens and the microbiome of fruit received at a processing plant representing early mid and late seasonal fruit as well as out of season fruit cold stored using viable and non-viable comparative methods. The microbial impact of a commercial washing step with a broad-spectrum surface sanitiser followed by a peracetic acid disinfectant, was also determined to assess ultimate safety of the product. The findings in this study demonstrated diverse bacterial taxa associated with the avocado fructomicrobiome. After fruit washing it was noted that the overall bacterial load decreased, but coliform counts increased. This indicates that the fruit wash water might potentially contaminate the fruit and contribute to the bacterial load of the fruit carpoplane. Two foodborne pathogens were detected from avocado fruit, Escherichia coli, which decreased after fruit washing and Salmonella enterica subsp. enterica serovar Typhimurium which was predominantly isolated from the avocado pulp. This study contributes to an improved understanding of the bacterial communities and major foodborne pathogens associated with avocado fruit in the processing environment. The study also provides some insight to the core avocado microbiome. Further research focussing on a broader spectrum of farms and processing plants could provide more generic information for the establishment of an industry food safety regulatory standard which can be used as a guideline by the industry.Dissertation (MSc (Plant Pathology))--University of Pretoria, 2020.Plant Production and Soil ScienceMSc (Plant Pathology)Unrestricte