Canning and Fish Packaging Technology

Unit 4 - Thermal process for canned foods

4.4.Relationship between acidity and severity of the process
This is best illustrated by the following tables.

Acidity of Food and Example	Severity of thermal process
High - Citrous fruits pH 3.7 or less - Pineapple	Low - 5 Min at 80OC The process is known as pasteurization
Medium - Pear, tomato pH 3.7 – 4.5 - Apple	Medium - 15 min at 100OC
Low - Meat ; fish pH 4.5 or more - Corn, green vegetables	High – 60 min 121.1OC The process is known as sterilization.

To make canned foods sterile may not be necessary sometimes because food may lose all its sensory qualities. In such cases, rather than making the canned foods absolutely sterile, processor aims at commercial sterility which is aimed at killing the most heat resistant pathogenic and spoilage bacteria at that particular pH of food. The essential condition necessary for commercial sterility is that there be no health risks arising from microorganisms that survived the thermal process which means Clostridium botulinum (the most severe food poisoning bacterium), other relatively less heat resistant pathogenic organisms and spoilage bacteria are killed. The survival of other heat resistant non pathogenic bacteria may be may not affect the food.