Comparative study on the fillet nutritional quality of diploid and triploid rainbow trout (Oncorhynchus mykiss)

This study was conducted to investigate the fillet nutritional quality difference of diploid and triploid rainbow trout with the same genetic background, farming condition and body weight. The results showed that, 1) diploid rainbow trout had significantly higher content of protein, valine, cysteine, histidine and proline, and higher essential amino acid index, nutrition index and biological value than triploid rainbow trout (P < 0.05). However, essential amino acids and total amino acids contents as well as amino acid score and chemistry score were similar between the two fish (P > 0.05), which indicated that both diploid and triploid rainbow trout fillets were balanced and suitable for human consumption. 2) Triploid rainbow trout had significantly higher content of lipid, C18:1n-9, C18:2n-6, C20:5n-3, C22:6n-3, unsaturated fatty acids (UFA), polyunsaturated fatty acids (PUFA), long chain polyunsaturated fatty acids, n-3 series fatty acids, n-6 series fatty acids and total fatty acids (TFA) than diploid rainbow trout (P < 0.05). However, no differences were found in saturated fatty acids (SFA), C18:3n-3 and C20:4n-6 contents between the two fish (P > 0.05). Based on PUFA/SFA, UFA/SFA, PUFA/TFA, atherogenic index, and thrombogenic index, both diploid and triploid rainbow trout consumption were beneficial for human health, triploid fish had an even greater advantage. 3) Triploid rainbow trout had higher content of sodium, calcium, iron, manganese and zinc but lower content of magnesium, copper and selenium than diploid rainbow trout (P < 0.05). Multivariate statistical analysis of 79 quality indicators also showed that the fillet nutritional composition of triploid rainbow trout was different with its diploid counterparts. The reason may be related to the difference of lipid metabolism in rainbow trout with different ploidy.