Dynamics of water mobility, salt diffusion and hardness changes in bighead carp fillets during low-salting

Abstract

Low-salt fish as a traditional preserved food has gained growing popularity for the reduction in sodium consumption. Water transport, salt diffusion, and hardness changes of bighead carp fillets were investigated by low-field nuclear magnetic resonance (LF-NMR), electric resistance, and texture profile analysis (TPA) under salting concentration of 15 mg/g and 30 mg/g. The decrease of P21 (T21 population) by LF-NMR analysis of G0 (control) was 12.1% while that of G1 (15 mg/g) and G2 (30 mg/g) was 2.2% and 5.3%, respectively. Meanwhile, the diffusion of salt was fast in the first 30 min, and the higher the salt concentration, the lower the resistance value. Furthermore, the higher hardness in G1 was observed, reaching 2.17 times that of control. At the end of salting, the proportion of P21 (Y1) and change of hardness (Y3) showed negative linear relationship with salt content (from 15 mg/g to 60 mg/g): Y1 = −0.0094 x + 0.9702 and Y3 = −0.1752x + 2.3544, and the resistance change rate (Y2) showed a positive correlation: Y2 = 5.9722x + 0.5625. The established model could effectively predict the hardness and water mobility of bighead carp fillets during the early stage of salting process.