An emission pattern of a thermophilic bacteria attached to or imbedded in porous supports

There are many problems with thermophilic bacteria contamination of milk in the dairy industry. This is, in part, a result of fouling by milk components on stainless steel surfaces, which provide good harboring facilities for these bacteria to attach, imbed and grow. The interactions between milk fouling and bacteria deposited in or on the fouling deposit therefore become important issues. There have been a number of previous studies on the biofilm development in dairy processing plants. Here, a different approach to investigate the bacteria emission from a porous layer has been taken. In this approach, various process fluids were flushed over the top of a model milk foulant layer that contains high percentages of milk proteins, fat and some bacteria cells, in order to investigate the behavior of the ‘resident’ microorganisms and how they are ‘released’ into the flushing liquids. Definitive results were obtained, which have created sufficient interest for a different approach taken later, where fabric layers were used as the support for the bacteria cells to explore the ‘generic’ behavior of the porous layer–bacteria system. This study has shown that Bacillus stearothermophilus could multiply on or within a porous layer and ‘migrate’ from the layer into the fluid during processing. This “migration” is somewhat peculiar in terms of its time-responses but these are reproducible in all the tests performed. The phenomena observed may have an impact on future microbial safety practice in food factories.