Canning and Fish Packaging Technology

Unit 3 - Unit operations in canning

3.2.4.1.Purpose of can closing /seaming

• To prevent loss of vacuum produced during exhausting.
• To create a barrier between the food inside the can and outside atmosphere in order to prevent contamination of food.
• To prevent loss of moisture from the food in the form of liquid or vapour packed inside the can.
• To prevent chemical changes that takes place in food when exposed to atmosphere/air.

In conventional canning procedure can closing is done after exhausting but before thermal processing. If the cans are properly closed, thermal processed food in the can in which microorganisms are destroyed will not get recontaminated. In modern methods, such as aseptic canning it may be different. Several containers were being used in the canning. For example, bottle and closure, complete soldered cans, hole and cap/lid cans etc. Later single seaming and finally double seaming of cans were followed. At present, only double seaming is followed and hence the further discussion on double seamers.