Abstract:To investigate the effects of different thawing methods on the oxidation characteristics of protein after in vitro gastrointestinal digestion, four thawing methods, namely cold storage thawing (CST), MNPs combined ultrasonic thawing (NUT), MNPs combined microwave thawing (NMT), and MNPs combined ultrasonic-microwave thawing (NUMT), were used to simulate the gastrointestinal digestion of jumbo squid (Dosidicus gigas) in vitro. The results showed that compared with the control group CST, the three thawing methods all improved the digestibility of protein. The protein digestibility in vitro of the NUMT treatment group was up to 80.33%. The degree of protein oxidation in the NUMT group was the lowest after gastrointestinal digestion. Specifically, the carbonyl content was 2.66 nmol/mg in the stomach and 3.86 nmol/mg in the intestine; dipolytyrosine levels were reduced by 30.75% in the stomach and 23.73% in the intestine compared to the CST group; the sulfhydryl group contents were 19.25 nmol/mg in the stomach and 18.68 nmol/mg in the intestine. Additionally, the particle sizes of the NUMT group were the smallest, measuring 298.41 nm in the stomach and 327.48 nm in the intestine. The DPPH free radical scavenging rate and Fe2+ chelating ability in the NUMT treatment group were the highest, reaching 56.94% vs 25.59% in the stomach and 58.72% vs 32.27% in the intestine, respectively. In conclusion, under the four different thawing methods, the NUMT treatment group significantly reduces protein and lipid oxidation during the thawing process of jumbo squid, demonstrating the highest antioxidant activity following gastrointestinal digestion.