Changes in white tuna (Thunnus alalunga) fat due to cannig process and storage preserve

Abstract

Modifications in fatty acid composition in white tuna (Thunnus alalunga) ocurring at each stage of the cannig process, boiling and sterilization in soybean oil, were studied. Boiling was performed in brine and two sterilization times (55 and 90 minutes) as well as the effects of storage for one year were tested. Boiling had no effect on fatty acid composition or the n-3/n-6 ratio. However canned tuna absorbed soybean oil during sterilization, causing an increase of the percentage of C18:1, C18:2 and C18:3 and a decrease in C20:5 and C22:6. Therefore, unsaturated fatty acids to saturated fatty acids (PS/S) ratio changed and the n-3/n-6 ratio declined from 7.03 to 0.59 compared with raw tuna. Due to the whole fat enrichment, canned fish showed a slight loss of PUFA (C20:5 and C22:6) and a increase of C18:1, C18:2 and C18:3. The latter effect was more marked in the preserves as a consequence of one year storage. The convenience of using for cannig an oil containing a lower amount of polyunsaturated fatty acid in order to remain the original n-3/n-6 ratio of the raw tuna is discussed.