Protein degradation and aggregation in silver carp (Hypophthalmichthys molitrix) muscle during hot air drying

This research was to investigate protein changes (protein molecular weight distribution, free amino acid (FAA), cathepsin activity) in silver carp ( Hypophthalmichthys molitrix ) muscle during the process of brine curing (10 g/L s alt, 4 °C, 3 h) and air-drying (45 °C, 24 h). The results showed that after air-drying for 4 h, the proportion of protein aggregates with molecular weight >1000 kDa increased by 7.47% compared to fresh fish. Meantime, activities of cathepsin B and B + L increased from 1.52 ± 0.35 and 2.05 ± 0.45 U/g to 2.33 ± 0.22 and 3.27 ± 0.18 U/g, respectively. However, total FAA content had not significantly different ( P > 0.05) in this drying period. Thus, although protein aggregation and protein degradation occurred simultaneously, protein aggregation was dominant in the early stage of drying processing. And the protein aggregation decreased, and total FAA content increased, activities of cathepsin decreased but remained relatively high with continuous drying. Thus, protein changes in silver carp muscle were mainly due to degradation. Protein analysis in this study favored to understand the silver carp muscle changes during drying processing and supported to improve freshwater fish drying processes. • Protein degradation occurred over drying processing of silver carp. • Aggregation of the protein is dominant in the early stage of drying processing. • Protein analysis favored to understand the muscle changes during drying processing. • The results supported to improve freshwater fish drying process.