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S. BRUL1, F. Schuren2, R. C. Montijn3, B. Keijser4, S. Oomes5, and H. Van der Spek4. (1) Molecular Biology and Microbiological Food Safety, Univ. of Amsterdam, Nieuwe Achtergracht 166, Amsterdam, 1018 WV, Netherlands, (2) Dept. of Risk Management and Microbiology, TNO Nutrition & Food Research, PO Box 360, Zeist, 3700 AJ, Netherlands, (3) Dept. of Risk Management and Microbiology, TNO Nutrition and Food Research, PO Box 360, Zeist, 3700 AJ, Netherlands, (4) Dept. of Molecular Biology and Microbial Food Safety, Swammerdam Institute for Life Sciences, Swammerdam Institute for Life Sciences, Amsterdam, Netherlands, (5) Dept. of Microbiological Control, Unilever Food Research Center, Unilever Research and Development, Olivier van Noortlaan 120, Vlaardingen, Netherlands In the food processing industry, extremely heat resistant bacterial endospores create problems due to their ability to survive exposure to conventional thermal treatments, and then subsequently germinate and form actively growing vegetative cells. We focus on studies of the genus Bacillus and discuss particular examples. Amplified Fragment Length Polymorphism (AFLP) analysis and micro-array technology of food spoilage isolates has identified a number of genome factors that correlate with the level of heat resistance of spores. Strains could be classified for their heat resistance based on the presence of these genome factors. In addition, the presence of calcium ions in a cocktail of minerals was shown to promote the thermal resistance of developing spores using a sequenced laboratory strain. This enrichment with calcium ions has been suggested to correlate with an increased level of dipicolinic acid. These physiological observations were complemented with micro-array analysis that resulted in the identification of an increased expression of genes encoding small acid soluble spore proteins during sporulation of the cells (Oomes and Brul, 2004 IFSET). Finally, we will discuss the experimental approach that is currently followed to characterize stress-induced damage of spores and its repair. In particular, we discuss a stress-induced delay in spore outgrowth and (altered) germination relating to specific gene-expression patterns. The data suggest the existence of preprogrammed repair mechanisms operative during initial stages of germination. Various projects have been or are being set-up that aim to integrate genomics data and micro(nano)-technology, a prerequisite if the suggested Food (ingredient) Quality Control is going to succeed. Based on information to be gained from these projects on the one hand and the requirements of product organoleptic quality on the other hand, we will be able to derive robust integrated food safety and food quality processing parameters. These parameters should form the basis of Food Quality Assurance systems.
Session 9, Mechanisms and modeling of bacterial spore inactivation by high pressure processing
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |