VARIATIONS IN FLAVOR ACCORDING TO FISH SIZE IN RAINBOW TROUT Oncorhynchus mykiss

Rainbow trout (Oncorhynchus mykiss) is popular with consumers because of its delicate meat, smooth taste, bright color and high nutritional value, and is widely cultured in many countries. Fish quality is influenced by fish size as well as several other factors, including intrinsic (species, sex, and sexual maturity) and extrinsic factors (season, water temperature, salinity, and source of nutrients). The objective of this study was to evaluate the flavor qualities of the dorsal, tail, and abdominal muscles of four sizes of the rainbow trout.

Fresh triploid rainbow trout were collected at the same time in July 2018 from net cages in Liujiaxia Reservoir, Gansu Province, China. China. Four groups of fish were caught randomly from four different net cages; the average weights were 0.25 ± 0.06, 1.14 ± 0.09, 2.26 ± 0.24, and 2.89 ± 0.22 kg (Abbreviated as S1, S2, S3, and S4 groups, respectively). Results of this study showed the changes of flavor compounds in three tissues from rainbow trout of four sizes (Fig. 1). Notably, dorsal and tail tissues of rainbow trout seem to have superior quality than abdominal tissues. The S2 group had the highest levels of total free amino acid (FAA), the S1 and S2 groups had higher levels of sweet amino acids, and the S4 group had the highest levels of lactic acid and succinic acid. In fresh rainbow trout, the predominant nucleotide was Inosine-5’-Monophosphate (IMP). Electronic tongue analyses demonstrated taste differences for three tissues from rainbow trout of varying sizes. Differences were observed in fatty acids profiles for dorsal tissues, with large fish having significantly higher monounsaturated fatty acid (MUFA) contents and significantly lower polyunsaturated acid (PUFA) contents. The smallest fish (S1 group) had the highest docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) contents. Based on these data, it indicates that fish size and tissues had variable effects on the flavor profiles of rainbow trout. In addition, using fish size to describe fish flavor may have applications in markets and could provide important information for consumers. However, the molecular mechanism of flavor changes in rainbow trout during growth is not clear, its molecular mechanism needs to be further studied.