Canning and Fish Packaging Technology

Unit 5 - Changes in canned foods and spoilage

5.2.2.3.1.Under-processing
Second reason for spoilage of food can is ‘under-processing’. Under-processing may be due to several reasons listed below.

• Inadequate thermal process to kill the most significant microorganisms.
• Contamination by highly heat resistant organism not usually present in the food.
• Unusually high level of contamination by usual contaminant microorganisms.
• Faculty retort operation.
• Improper working of instruments fixed to the retorts.
• Air inside the retort due to incomplete venting.
• Changes in consistency, improper fill with respect to higher weight of solids, solid-liquid ratio, head space etc.
• Low initial temperature of the product.

In spoilt can due to the under processing, generally one type of heat resistant spore former is observed. Such cans give positive results during microscopic examination and also in culture. High degrees of swelling such as soft and hard swell are observed. In fish cans, the hardness of bones indicates whether the can is under processed.