Gender and sexual maturity differences in muscle nutritional components and evaluation of nutritive value in Schizothorax lissolabiatus from Beipan River

【Objective】 To investigate the nutritional value of Schizothorax lissolabiatus muscle in the Beipan River（Pearl River System）, and the nutritional differences related to gender and sexual maturation, which could provide scientific basis for research on muscle nutrition and development of artificial feed. 【Method】 Using 30 wild Schizothorax lissolabiatus samples from the upper reaches of the Beipan River as experimental materials, chemical analysis methods were employed to determine the conventional nutritional components, amino acid composition, and fatty acid content of their muscle tissue. A comprehensive evaluation on the muscle nutritional value was conducted, followed by a comparative analysis of the differences in muscle nutrition between sexually immature individuals and sexually mature individuals, as well as between female individuals and male individuals. 【Result】 The results showed that the average contents of water, protein, fat and ash among the conventional nutritional components in Schizothorax lissolabiatus muscle were 78.43%, 16.95%, 3.37% and 1.00% respectively. A total of 18 amino acids were determined in the muscle, glutamate was the most abundant but tryptophan the least. The total contents of 18 amino acids, 10 essential amino acids and 4 delicious amino acids in the muscle were high with averages of 79.14%, 36.99% and 25.63% respectively, and the F value of the muscle averaged 1.96. The muscle was abundant in lysine. The ratios of essential amino acids contents to total amino acids and nonessential amino acids contents were 0.47 and 0.91 respectively, which matched the standards proposed by the Food and Agriculture Organization of the United Nations/World Health Organization（FAO/WHO）, being arourd 0.40 and above 0.60 respectively. The essential amino acid index（EAAI） was relatively high, with an average of 66.20, and the protein quality was excellent. The first limiting amino acid was tryptophan, and the second ones were valine and isoleucine in the muscle. The contents of 26 fatty acids including 9 saturated fatty acids, 8 monounsaturated fatty acids and 9 polyunsaturated fatty acids were determined in the muscle, and the contents of oleic acid, palmitic acid, hexadecaenoic acid and linoleic acid were obviously higher. Among the unsaturated fatty acids, the contents of monounsaturated fatty acids（MUFAs）, linoleic acid, and n-3 polyunsaturated fatty acids（n-3 PUFA） were relatively high. The ratios of polyunsaturated fatty acids to saturated fatty acids （∑PUFA/∑SFA） and n-3 PUFA to n-6 PUFA （∑n-3 PUFA/∑n-6 PUFA） were also high, with average values of 0.87 and 0.13 respectively. No significant differences were observed in the conventional nutritional components of muscle—including moisture, ash, protein and fat content—between sexually immature individuals and sexually mature individuals or between female individuals and male individuals（P＞0.05）. Regarding muscle protein nutritional value, male individuals exhibited superior quality compared to female individuals, while sexually immature individuals had better umami levels than sexually mature ones, and female individuals showed higher umami levels than male individuals. In sexually immature individuals, the contents of MUFAs and arachidonic acid were significantly lower than in sexually mature individuals（P＜0.05, the same below）, whereas essential fatty acids and n-6 PUFAs contents were significantly higher than sexually mature individuals. Additionally, muscle in female sexually mature individuals had significantly lower n-3 PUFAs and eicosapentaenoic acid（EPA） content than male sexually mature individuals. 【Conclusion】 The muscle of Schizothorax lissolabiatus contains low content of fat and high nutritional value of protein and fatty acids, as well as good flavor, and therefore Schizothorax lissolabiatus is an edible economic fish with high quality.