III.1. Filling and sealing

The fish are often pre-processed after the usual heading, gutting, cleaning, and trimming operations by for example, salting, brining or smoking. These operations denature the protein, and make the flesh firmer and less subject to fragmentation. They also remove some water and thus make the fish less subject to shrinkage in the can, improve the appearance of oil packs and prevent the dilution of sauces. Air, which may produce some rancidity in the product, is removed from the container by sealing under vacuum.