Canning and Fish Packaging Technology

Unit 3 - Unit operations in canning

3.2.3.5.Air inside food cans
Air, gases and vapour from liquids of a food can exist in the head space which is removed by exhausting. In solid foods covered with a liquid filling medium and when the liquids do not cover the solids completely, air will be entrapped. Similarly when liquids are filled air bubbles in the liquid foods, air attached to cans will be there in filled and sealed cans. In fruits and vegetables there will be the substantial amount of tissue gases. Also if the liquids are filled into cans without heating, there will be substantial quantity of dissolved gases. If all the air, gases and vapour are not removed from the can and sealed, these will accumulate in the head space during heat processing and hence the vacuum inside the can will be less than what is required. Hence, it is important to remove these gases and vapors by exhausting.