Influence of sodium chloride and sodium pyrophosphate on the physicochemical and gelling properties of silver carp myofibrillar proteins sol subjected to freeze-thaw cycles

The effects of different content of sodium chloride (NaCl) and sodium pyrophosphate (SPP) on the stability of myofibrillar proteins (MPs) sol subjected to freeze-thaw cycles (F-T cycles), as well as the performance of heat-induced gel subsequently formed from the frozen-thawed MPs sol, were investigated. The molecular states of MPs with high NaCl (15 g/kg, 25 g/kg) and additional SPP (1 g/kg, 3 g/kg, 5 g/kg) were altered due to the cross-linking and aggregation, showing the larger turbidity, higher surface hydrophobicity, and intrinsic fluorescence intensity. Additionally, compared with the control and 5 g/kg NaCl groups, MPs sol with high NaCl content exhibited less proteins denaturation and higher stability of water molecules after 2 F-T cycles. However, the poor gel properties were observed in high NaCl groups with larger cooking loss, weak gel strength, inferior textural parameters, and disorganized micro-network structure, revealing cross-linking and aggregation of MPs during F-T cycles were negative to the gelling properties. Furthermore, the additional SPP (1 g/kg) significantly inhibited protein aggregation and water migration during F-T cycles of MPs sol, resulting in superior gel properties with ordered gel microstructures.