Canning and Fish Packaging Technology

Unit 5 - Changes in canned foods and spoilage

5.2.Spoilage in canned foods
For any reason, if the food packed inside the can is not acceptable for human consumption such a can is considered as spoiled can.
It is very difficult to ascertain whether the food is good or bad by external attributes of a can. When the food inside is spoilt, gases are generated which exert pressure on the can ends and the cans bulge. If the can ends are convex or bulged, it can be generally assumed that the cans are spoilt. Bulged cans cannot be marketed. Even though bulged cans are rejected, food inside such can need not be inedible on all occasions. Spoilage of food inside the can need not be the only reason for bulging of cans.
Some bacteria (e.g. B.stearothermophilus) do not produce gas when it spoils food. In such cases, even though the food inside is spoilt, the cans appear good with flat ends. In such cans the acidity will be high (low pH) and the food develops sour taste. Hence it is known as ‘flat sour spoilage’.