The effect of sanitiser technologies on the growth of biofilm and non-biofilm Listeria monocytogenes
Listeria monocytogenes is a pathogen which causes the human disease, listeriosis, which can result in death. The ubiquitous nature of the organism throughout nature means it can also be found in food processing facilities. This organism can also persist in food processing facilities due to the fact that it can grow at refrigerated temperatures and form biofilms on stainless steel equipment. Listeria monocytogenes has developed certain resistance mechanisms to commonly used sanitisers that are used in factory cleaning. My job is to develop an optimal treatment regime for the food industry against L. monocytogenes which show resistance to certain sanitisers in both the biofilm (sessile) and non-biofilm (planktonic) state. My research will result in a better understanding of factory cleaning and optimised regimes for sanitiser applications, which will ultimately result in safer food production.
A One Health approach: Categorization of Listeria monocytogenes from food, environmental, and clinical origin in the Western Cape (South Africa)
My study is focused on the well known food pathogen, Listeria monocytogenes and its related virulent strains which are responsible for causing listeriosis, a disease often fatal for immunocompromised individuals. Despite the significant public health risk posed by virulent strains of L. monocytogenes, very little research has been generated from sub-Saharan Africa regarding the distribution of L. monocytogenes strains in the food environment and the associated public health risk. Thus, this study aims to fill the gap between food and clinical strains, and to investigate potential links between these two areas. I am also investigating the antibiotic resistance of these strains, as well as its susceptibility to a commercial bacteriophage.
The investigation of Listeria spp. in the South African ready-to-eat processed fruit supply chain
Fresh-cut tropical fruits, an important source of carbohydrates, vitamins, minerals and fibers, are particularly attractive to consumers all over the world. This is seen in the growing demand for processed fruit products, however their association with foodborne pathogens, particularly Listeria monocytogenes, has become a growing concern. In order to effectively manage the prevalence of Listeria monocytogenes within the processed fruit supply chain, a holistic investigation of all Listeria species present from growers to processors will be of significant value. This research project focuses on papaya and cantaloupe and aims to gain insight into the ecology and distribution of Listeria spp. in the processed fruit environment, to investigate any changes in the distribution of Listeria species throughout the food supply chain and to identify the points where intervention is required to ensure food safety.
The effect of different honeybush (Cyclopia subternata) levels in warthog (Phacochoerus africanus) salami
Salami is part of a gustatory history truly worth appreciating. Salting and stuffing of highly perishable meat and fat into animal intestines dates back to antiquity and ensured a meat supply lasting up to months. The revolutionary discovery of saltpeter (potassium nitrate) contamination in salt resulting in the well-known stable, cherry red meat colour paved the way for the commercial application of nitrate and nitrite salt in a variety of processed meats and cheeses. Nowadays the curing agents, sodium and/or potassium nitrate and nitrite are commonly applied in cured meats due to their potent antioxidant and antimicrobial effect, especially against the lethal and feared Clostridium botulinum. Unfortunately, the food safety benefits of using these salts are challenged by the potential human adverse effects in the case of nitrite chemistry, resulting in the formation of n-nitrosamines which are known carcinogens. The ongoing debate, controversial conclusions and consumer demands create a tremendous challenge for the meat industry, as food safety is and should always be the number one priority. An abundant amount of research has been invested in the use of natural extracts, essential oils and herbs which exhibit antimicrobial and/or antioxidant activities to try and mimic the effect of nitrate and nitrite in processed meats. There is yet to be a single replacement found for these multi-functional curing agents. A potential ingredient, honeybush will be investigated as a potential replacement. Honeybush is an endemic South African shrub enjoyed as hot brewed tea once the leaves and stems are fermented. This plant has proven to be rich in polyphenolics and has shown antioxidant activity. The aim of this project is to test the effect of honeybush extract in warthog salami with reduced added sodium nitrate. Physical chemical analysis will be conducted on the salami and includes: pH, water activity, CIEL*a*b surface colour, texture profile analysis, proximate analysis, free fatty acid and lactic acid titration. Final product microbial analysis will also be conducted and will provide insight surrounding the food safety aspect.
Extracellular proteases and their application in commercial yeast
This project aims to tackle a part of the major global concern of food wastage.
Millions of tons of bread are thrown away on an annual basis, generally ending up as animal feed or being disposed of. Wasted bread can be used as a valuable source of energy as it is high in carbohydrates that can be converted to simple sugars and then fermented by yeast to produce ethanol. The carbohydrates can be broken down into simple sugars by genetically modifying amylase (carbohydrate degrading enzymes) to produce yeast with proteases (protein degrading enzymes). The yeast could possibly break down the carbohydrates and proteins in the bread. This modification step may aid in the ability of yeasts to produce ethanol from old bread, a valuable by-product.