FFoQSI: 2.3.2 Spoilage of dairy products by endospore forming bacteria

The dairy industry encounters many difficulties with endospore-forming bacteria. Via faeces, dirty udders/teats, feed, bedding material and milking equipment, these bacteria can contaminate raw milk, both in vegetative state and in their heat-resistant dormant (endospore) form. Within this context, the genus Clostridium is particularly relevant because clostridia cause late-blowing, a severe quality defect in hard and semi-hard cheese. A disorganized internal structure and irregular cheese eyes due to excessive gas production characterise affected cheeses. Furthermore, the production of butyric acid results in pronounced off-flavours. Within the scope of the K project “ADDA - Advancement of dairying in Austria”, a semi-automated most-probable-number (MPN) approach, that allows a timely quantitative detection of clostridia, was developed. The format was established, selective media were optimised and tested, and appropriate read-out systems were designed. Finally, the test system was evaluated using raw milk as food matrix. As part of the FFoQSI (Food and Feed Quality Safety and Innovation) project, the developed MPN method will be optimised and validated. Additionally, the analysis of cheese, raw milk and samples from stable and cheese production environments shall lead to a better understanding of microbial activities and blowing defects during cheese ripening. Based on the obtained knowledge, measures can be taken to avoid quality defects in cheese.