Effect of dietary phosphorus on physicochemical properties, composition of free amino acid, flavor nucleotide and free fatty acid in muscle of grass carp (Ctenopharyngodon idella)

To assess the effect of dietary phosphorus on physicochemical properties, composition of free amino acid (AA), flavor nucleotide and free fatty acid in muscle of grass carp, a 60 d growth trial by feeding graded levels of available phosphorus (0.95-8.75 g/kg diet) was conducted. Results demonstrated that optimal available phosphorus levels increased the protein and hydroxyproline contents and pH value, while decreased the contents of lipid and lactate, cooking loss, shear force, and cathepsin activity to improve fish muscle physicochemical characteristics. In addition, optimal available phosphorus levels increased the contents of total essential amino acids (EAAs), umami taste AAs, sweet taste AAs and inosine monophosphate (IMP) contents enhancing fish muscle flavor. In addition, when the available phosphorus level in the feed was increased to 3.96 and 5.68 g/kg, the taste activity value (TAV) of IMP and total taste amino acids (UAAs+SAAs) reached the maximum values in fish muscle, respectively. And optimal available phosphorus levels increased muscle total polyunsaturated fatty acids (PUFAs) contents and the fatty acid ratio of PUFAs/saturated fatty acids (SFAs), and n-3/n-6. In conclusion, appropriate available phosphorus supplementation improved flesh quality, which might be in part attributed to the enhancement of tenderness, water holding capacity and pH, and increase of flavor amino acid, nucleotide and PUFAs contents in muscle of fish.