Lesson 08: Preservation by Use of HeatPreservation by Use of Heat
Sterilization
Sterilization refers to complete destruction of microorganisms. It requires heat treatment of 121°C for 15 minutes which destroys all spores. But it has severe effect on heat sensitive nutrients and proteins through maillard reaction. The temperature and time required to sterilize the food varies with the type of food. Such high temperatures can be created by steam under pressure in steam pressure boilers/ sterilizers. Temperature at sea level is 100°C at atmospheric pressure but with 15psi temperature of 121.5°C can be achieved.
Commercial sterilization: Commercial sterility is achieved when all pathogenic and toxin forming microorganisms have been destroyed along with the spoilage microorganisms. Usually target organism is a heat resistant microorganism, most often a spore or schlerotia forming organism rather than a vegetative one (e.g. spore forming anaerobic bacteria – Clostridiumbotulinum). Such foods may contain viable spores but these are not able to grow under normal conditions. If packaged aseptically, these products can be marketed without refrigeration. These products generally have a shelf life of 2 years or more.
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