Canning and Fish Packaging Technology

Unit 3 - Unit operations in canning

3.1.4.1.Salt
Salt is used in the preparation of brine and the concentration of salt used may vary from 6-8% to saturated salt solution. Brine is used for dip treatment to dressed fish prior to canning, blanching of peeled and deveined prawns (6 to 8% boiling brine) and as filling medium (1-3%) salt in fish cans. The brining improves the texture of the fish.

The impurities in salt such as chlorides and sulphates of magnesium will lead to bitter taste of the product. If the above mentioned magnesium salts are present in more than 0.1% in canned fish, it results in the formation of ‘struvite crystals’. Struvite crystals are glass like structures and are undesirable in canned products.

Quality of salt used for canning

• The salt used in canning should be pure and should not contain more of soluble and insoluble impurities. The soluble impurities should not be more than 1.5% and insoluble impurities should not be more than 0.5% when it is used for can filling.
• The counts of halophilic bacteria and pathogenic bacterial spores in salts should be low.
• The salt should have minimum of 98% sodium chloride content, should be of small crystal size for easy dissolution. Some table salts are added with Magnesium carbonate and Calcium carbonate to maintain free flow characteristics and hence such salts have to be avoided.