Differentiation of common marketable-size rainbow trouts (Oncorhynchus mykiss) based on nutritional and dietetic traits: a comparative study

In order to prepare a complementary guideline in nutritional quality for selecting an appropriate market-size rainbow trout, proximate composition, fatty acids' profile and sensory properties of most available market-size trout with three different average weight of 225 +/- 25 (low weight, LW), 350 +/- 30 (medium weight, MW) and 480 +/- 30 g (high weight, HW) were evaluated. Lipid and protein contents showed a tendency to increase with weight. The ratios of n-6/n-3 polyunsaturated fatty acids (PUFAs) (1.01-1.59) in present study were lower than the recommended harmful value of n-6/n-3 PUFAs ratio (4.0 at maximum). In general n-3 PUFAs, especially docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) levels indicated a tendency to decrease with weight. Also, with increasing weight, increasing trends of DHA/EPA and n-6/n-3 PUFAs ratios were found. Lower atherogenic index (AI) and thrombogenicity index (TI) values were observed in HW and MW trout in comparison with LW trout (P<0.05). There was no significant difference in odour and texture of studied trout fillets, while colour of samples significantly differed between treatments. It is worth mentioning that MW market-size trout for its attractive colour in judges' view showed higher general acceptability scores (P<0.05). In most of studied parameters any significant difference was observed between MW and HW trout. Therefore, it can be concluded that the MW trout was considered as high-quality market-size trout' for human consumption.