Effects of hydroxyl radicals oxidation on digestion properties of silver carp myofibrillar protein gel

Abstract

The generation of hydroxyl radicals from fat oxidation during frozen storage of surimi has been confirmed to induce oxidative cross-linking of proteins, but the further effect on their digestive properties and nutritional qualities is still unclear. In this work, a simulated system composed of the silver carp myofibrillar protein (MP) and Fenton system was used to study their digestive process and activities. Affected by oxidative cross-linking, oxidized MP gels were slowly and incompletely hydrolyzed by gastrointestinal process according to free amino content, particle size and peptide amount. However, the essential amino acid proportion, reduced power and hydroxyl radical chelation of digestion products from slight oxidation group (0.1–0.5 mM H2O2) were found to be generally stronger than over-oxidation group (5.0–10.0 mM H2O2). Furthermore, the in vitro biological evaluations confirmed that there were certain antioxidant activities of digestion products without potential cytotoxicity on HepG2 cells. Oxidation treatment on MP was found to negatively maintain SOD activity and generating GSH. Nevertheless, the slight oxidation group showed great protection effects to keep HepG2 cells from cell membrane damage and release LDH. In conclusion, the slight oxidation of MP is beneficial to improve the nutritional quality and in vitro antioxidant activity of its digested products.