Effect and mechanisms of mechanical pre-dehydration treatment on gelling and physicochemical properties of unwashed silver carp (Hypophthalmichthys molitrix) surimi.

Washing improves the overall quality of surimi production. However, the washing process significantly increases wastewater discharge from factories, thus raising environmental concerns and highlighting the need for more sustainable methods of surimi production. This study aimed to investigate the possibility of improving the quality of unwashed freshwater surimi by mechanical pre-dehydration and to explore the changes in gelling properties and physicochemical characteristics during frozen storage. The results indicate that the gel strength and water-holding capacity (WHC) of mechanically pre-dehydrated unwashed surimi can reach 522.50 g·cm and 68.12 %, which were equivalent to surimi subjected to two washes. During frozen storage, the pre-dehydration exhibited beneficial effects on the gel properties and water retention of surimi. Furthermore, SDS-PAGE analysis indicated that pre-dehydration retarded protein degradation during frozen storage. Indicators such as sulfhydryl groups, carbonyl content, protein solubility, and TBARS indicated that pre-dehydration could reduce the rate of protein and lipid oxidation. Focusing on the changes in endogenous components during the pre-dehydration, we showed that the dehydration could reduce the fat content (from 83.8 g/kg to 68.03 g/kg) and activities of cathepsin B (from 13.1 U/g to 7.3 U/g), lipoxygenase (from 621.3 U/g to 416 U/g), and gelatin-degrading enzymes in unwashed surimi, thereby enhancing the gel properties and frozen stability. Therefore, mechanical pre-dehydration can enhance the quality of unwashed surimi, thus providing a more environmentally friendly surimi production method.