Canning and Fish Packaging Technology

Unit 1 - Canning as a method of preservation

1.3.Steps involved in canning
The steps involved in the canning process are as follows.
Pre-processing operations: Depending on the nature of the food, different preprocessing operations are carried out. Washing, separation of edible parts, cleaning, cutting into desired size and shape, brining, precooking, blanching, frying etc are done prior to filling of the can. The difference in canning method for various foods stuffs lies in this stage.
Can filling:The preprocessed food is filled in to the cans along with suitable filling medium. The quantity of food to be filled varies with the size of the can. Sufficient space has to be provided between the lid and the top layer of the food.
Exhausting: The exhausting is the process to remove the air and gases inside the filled cans. This is achieved either by using steam or by creation of vacuum by a pump. The removal of air prior to can closing creates vacuum in the head space.
Can closing/seaming: Can closing or seaming is a process wherein, the lid and the body of the can are tightly sealed. This is done by can seamer. Can closing should be airtight preventing the exchange of gases between atmosphere and inside of the can.
Heat processing (Retorting): Retorting is a process where the closed cans are subjected to heat processing at high temperature to destroy spoilage and pathogenic microorganisms. This is the most important step in canning. The temperature and duration of heat processing depend on the type of food, size and shape of can
Cooling of the cans: After heat processing, cans are cooled immediately either in air or more commonly in water to the ambient temperature. Cooled cans are dried, labeled and stored.