10/20/2017 Physiology Physiology Temperature Strain can adapt to extreme environmental Temperature conditions ·Heat resistance -20C to 540c growth range increases in stationary phase cells pre-conditioning strains to cold or hot -increases when grown with high femperatures increases survival nutrients serious problems for the food industry increases as water activity of the Survives extended periods in food at food matrix decreases freezing and room temps and several factors will influence this Physiology Physiology Temperature pH Example:complex interaction of food, Grows at pH values ranging from 4.5-9.5 temperature,and organism ·Optimum pH6.5-7.5 -Salmonella survive on dry-roasted cocoa beans Pre-conditioned strains grown on pH gradient leads to contamination of in-line and finished plates can grow at a lower pH than the starting products cultures thermal inactivation of Salmonella in molten Raises concerns for fermented foods such as chocolate is difficult cured sausages and raw fermented milk products time needed would result in an unacceptable Starter culture used to acidify the foods product provide an environment that enhances Salmonella Salmonella survives for years in the finished survival in the read-to-eat product product Also promotes survival of Salmonella in the host 10/20/2017 6 Physiology Temperature • Strain can adapt to extreme environmental conditions - 2OC to 54OC growth range - pre-conditioning strains to cold or hot temperatures increases survival - serious problems for the food industry • Survives extended periods in food at freezing and room temps and several factors will influence this Physiology Temperature • Heat resistance - increases in stationary phase cells - increases when grown with high nutrients - increases as water activity of the food matrix decreases Physiology Temperature • Example: complex interaction of food, temperature, and organism - Salmonella survive on dry-roasted cocoa beans - leads to contamination of in-line and finished products - thermal inactivation of Salmonella in molten chocolate is difficult - time needed would result in an unacceptable product - Salmonella survives for years in the finished product Physiology pH • Grows at pH values ranging from 4.5-9.5 • Optimum pH 6.5-7.5 • Pre-conditioned strains grown on pH gradient plates can grow at a lower pH than the starting cultures • Raises concerns for fermented foods such as cured sausages and raw fermented milk products - Starter culture used to acidify the foods provide an environment that enhances Salmonella survival in the read-to-eat product - Also promotes survival of Salmonella in the host