SaFeMix – Safe fermentation of mixed dairy-plant bases

The dairy sector is rapidly adapting to current trends in consumer interests and sustainability issues with more emphasis on dairy products with varying degrees of plant material incorporated. While much is known about traditional milk-based fermentations in terms of pathogen prevalence and growth potential, the introduction of new plant-based ingredients into dairy products critically changes the pathogen risk profile. Sporeformers, in particular, are generally found in much higher levels in plant material and constitute a safety challenge due to the high heat resistance of the spores. SaFeMix aims to identify strategies for the control of B. cereus in mixed dairy fermentations.

By: Grith Mortensen

Introduction of plant material in dairy production, however, introduces new challenges for dairies in terms of food safety. Bacillus related problems are well known to the dairy industry. Due to their spores, Bacillus spp. can withstand harsh conditions including pasteurization, and they may compromise both safety and quality. The foodborne pathogen Bacillus cereus is estimated to be responsible for 1.4%-12% of all food poisoning outbreaks. Growth of B. cereus in food can lead to two types of disease. The ingestion of B. cereus and/or spores may cause a toxic infection and thus diarrhoea symptoms. Some B. cereus strains can also, during their growth in the food, form an acid- and heat-stable toxin, which causes poisoning if swallowed, and among other things causes vomiting. It is therefore necessary to be able to control B. cereus in fermented products. It increases complexity that growth and toxin production are affected differently by environmental and nutritional factors.

The scientists will identify strategies for the control of B. cereus in mixed dairy fermentations. A variety of strains including strains isolated from the dairy environment and raw materials will be characterized regarding genetic potential for toxin production and growth boundaries. A sensitive cereulide (toxin produced by B. cereus) detection method will be implemented. Spores from relevant strains will be tested for germination, outgrowth and toxin production in a range of fermentation processes involving different starter cultures, ratios of dairy:plant-based ingredients, temperatures, and acidification rates, as well as contamination levels of ingredients. At the end of the project the group will validate selected results under upscaled conditions.

The project will provide data that is in high demand for risk analysis and critical control points when introducing new ingredients in the dairy industry. It will identify critical limits in processing and evaluate potential protective cultures.