Canning and Fish Packaging Technology

Unit 4 - Thermal process for canned foods

4.7.Heat penetration in canned foods
The rate of heat penetration and the distribution of heat inside the can are other important aspects of thermal processing. These aspects are based on physical characteristics and completely independent of microbiological aspects. Neither the cans can be instantaneously heated to lethal temperature nor be cooled instantaneously. Food in the can passes through different temperatures at different times of heating and cooling processes. In order to understand how much sterilization the can has received, it is necessary to know how long the can has remained at each temperature levels. In other words, a complete picture of heating and cooling pattern is necessary for assessing the thermal process.

The distribution of heat within the can depends on how the heat is transferred. Food cans may be classified in convection heating packs and conduction heating packs depending on the type of heat transfer. Convection heating takes place when a liquid is heated and the liquid transfers the heat from one point to another by movement of liquid molecules within the can ie by convection. In case of conduction heating takes place when heat distribution takes place through solid.