Effect Of Tea Polyphenols On Flavour, Healthcare Components, Physicochemical Properties, And Mechanisms Of Collagen Synthesis In Growing Grass Carp (Ctenopharyngodon Idella) Muscle

Tea polyphenols (TP) are functional feed additives (antioxidants) derived from tea. Research to date has not investigated the impacts of TP on flavour quality, healthcare components, and physicochemical parameters of fish flesh. This study aimed to investigate whether dietary TP in growing grass carp could provide high quality fish flesh. 540 fish (187.49 +/- 0.66 g) were fed six diets with different concentrations of TP (0, 40, 80, 120, 160 and 200 mg / kg) for 60 days to determine the effects of TP on flesh quality. The results demonstrated that appropriate dietary TP supplementation benefits growing grass carp in the following respects: (1) promoting performance of growth and nutritional value of fish, (2) enhancing flavour of flesh by increasing the levels of umami-taste free amino acids (glutamic acid and aspartic acid) (3) increasing healthcare components of flesh particularly eicosapentaenoic acid (EPA 20:5n-3) and docosahexaenoic acid (DHA 22:6n-3), (4) improving physicochemical properties (firmness,pH, water-holding capacity) of flesh. The present research explores, for the first time, the effects of TP on enhancing the collagen content, which is partly correlated with the upregulation of type I collagen synthesis genes Col1 alpha 1 and Col1 alpha 2, mediated through transforming growth factor-beta 1 (TGF-beta 1) by Smad pathway in fish muscle. Based on growth performance (percentage weight gain) and fish flesh quality indices (EPA, DHA, shear force, and pH), the appropriate dietary supplementation of TP in growing grass carp were assessed to be 103.01, 116.30, 106.60, 141.15 and 113.49 mg/kg, using quadratic regression analysis. In summary, TP is a promising feed additive to improve fish flesh quality.