Identification and Changes in Fatty Acid Profile of Rainbow Trout (Oncorhynchus mykiss) Fillet During Frozen Storage (−18°C)

Abstract

This study was carried out to determine proximate analysis, fatty acid (FA) composition, and their changes in rainbow trout (Oncorhynchus mykiss) fillet during 10-month storage at −18°C. The results revealed that monounsaturated fatty acids (MUFAs) (33.8 %) were the more predominant of the total fatty acids, followed by saturated fatty acids (SFAs; 26.3%) and polyunsaturated fatty acids (PUFAs; 24.62%). Palmitic acid (21.09%) and oleic acid (18.54%) were determined to be the most abundant fatty acids of SFAs and MUFAs at the end of the experiment, respectively. Among n-6 PUFAs, linoleic acid (3.04%) and arachidonic acid (0.25%) had the maximum values at the end of the storage period, respectively. Eicosapentaenoic acid (EPA; 2.36%), linoleic acid (2.53%), and docosahexaenoic acid (DHA; 6.43 %) also showed the final dominance among n-3 PUFAs, respectively. The present study demonstrates that preservation of rainbow trout fillet under frozen storage could significantly affect its constituents by changes in SFA, MUFA, and PUFA and ratios of EPA + DHA/C16, n3/n6, and PUFA/SFA. Decrease in unsaturated fatty acids—especially PUFAs, EPA + DHA/C16, n3/n6, and PUFA/SFA ratios—showed that nutritional value of rainbow trout fillet had decreased, although it was always in the acceptable range for human consumption during the 10-month storage at −18°C.