Quality changes and the underlying physicochemical and microscopic mechanisms in black carp (Mylopharyngodon piceus) under various brining conditions

Effects of NaCl concentration (0.5 mol/L, 1.0 mol/L, 1.5 mol/L, and 2.0 mol/L) and brining time (1 h, 2 h and 3 h) on the water holding capacity, color, texture and the potential mechanisms were investigated in black carp. Brining in higher NaCl concentrations (1.5 mol/L and 2.0 mol/L) decreased the yield of black carp fillets. Brining in 0.5 mol/L NaCl solution increased the water weight, but the water holding capacity was significantly lower than other conditions ( p < 0.05). High salt concentration and long brining time promoted protein denaturation and degradation. Brining in 1.0 mol/L NaCl solution for 1 h could maintain better integrity of myofibers and promote the conversion of free water to bound and immobilized water. At this time, the fish fillet had better water holding capacity (90.78%), springiness (0.94) and cohesiveness (0.57). The improved water holding capacity and textural properties of black carp fillets were attributed to the modified microstructure and physicochemical properties, promoting the conversion of free water to bound and immobilized water. The present results could be a reference for the processing and quality control of lightly salted aquatic products. • Superiority of brining in 1.0 mol/L NaCl for 1 h enhanced WHC and texture of fillets. • Free water turned into bound and immobilized water after brining. • High salt concentration promoted protein denaturation and degradation. • Tissue shrinking and swelling occurred under various brining conditions.