CHANGES OF OMEGA-3 FATTY ACID CONTENT AND LIPID COMPOSITION IN CANNED TUNA DURING 12-MONTH STORAGE

ABSTRACT

The effect of storage time on the concentration and lipid and fatty acid compositions of canned tuna in brine was studied. Lipid and fatty acid were analyzed during 0, 3, 6, 9 and 12 months of storage at room temperature. Concentrations of lipids and total saturated fatty acids were significantly increased after storage for 9 months. The concentrations of total polyunsaturated fatty acids (PUFAs), total n-3 and n-6 PUFA were significantly stepwise decreased with increased storage time (P < 0.05); 22:6n-3 and 22:5n-3 started to decrease significantly at 6 months, and 20:5n-3 and 20:4n-6 decreased at 3 months (P < 0.05). The n-3/n-6 ratio significantly decreased from 3.8 at 0 month to 3.2 at 9 months (P < 0.05). Cholesterol ester was significantly increased while the other four classes of lipids, namely, phospholipids, triacylglycerols, free fatty acids and sterols, showed an opposite trend during 12 months of storage. Lipid oxidation measured by peroxide value and thiobarbituric acid value showed gradual increases with storage time. Thus, canned tuna in brine should not be stored more than 6 months with consideration of the stability of n-3 fatty acids.

PRACTICAL APPLICATIONS

Canned foods are significant dietary items, especially for bush walkers, travelers and armed service personnel. Canned fish, one of the important sources of long-chain n-3 polyunsaturated fatty acids (PUFAs), have an equivalent n-3 PUFA content as fresh fish. Long-chain PUFA in fresh fish is unstable and easy to oxidize. Appropriate process produced canned fish have a number of advantages such as odor, taste, shelf life, storage and carrying compared with fresh fish. We have investigated the lipid oxidation and fatty acid alteration sequentially during a 12-month storage because there has been no such data available in the literature. The data from the present study could provide useful information for industries, consumers and public health workers.