Effects of Aquaculture Modes and Thermal Processing Methods on in Vitro Digestive Properties of Tilapia Meat

This study aimed to investigate the effects of different aquaculture modes on the thermal processing and digestive characteristics of tilapia meat (Oreochromis niloticus). Tilapia meat from a recirculating aquaculture system (RAS) and a traditional aquaculture pond (TAP) was cooked by boiling or roasting and subjected to in vitro simulated digestion. Protein digestibility was determined and the crude peptide content, particle size, microstructure, and antioxidant activity of the digestion products were systematically analyzed. The results showed that in the gastric digestion stage, the digestibility of raw, boiled and roasted fish was significantly 3.1%, 3.5% and 2.2% higher in the RAS group than in the TAP group, respectively (P < 0.05), the highest value being observed in the boiled fish. The crude peptide content of gastric digestion products in the RAS group was significantly increased by 26.7%, 12.5%, and 23.3%, respectively (P < 0.05). In the intestinal digestion stage, the boiled RAS fish had the highest crude peptide content (5.4 mg/mL), the smallest average particle size (810 nm), and the lowest protein residue, indicating the most complete digestion. Antioxidant analysis showed that the intestinal digestion products of the boiled fish had the strongest free radical scavenging capacity, while no significant difference was found between the roasted and control groups. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis revealed weaker protein bands at 16−37 kDa in the gastric digestion products of the boiled RAS fish, indicating higher digestion degree. Two-way analysis of variance (ANOVA) showed that the interaction between culture system and thermal processing had a significant effect (P < 0.05) on the crude peptide content and 2,2’-biazobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cation radical scavenging capacity of the gastric and intestinal digestion products as well as the 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH) radical scavenging capacity of the intestinal digestion products. In conclusion, RAS combined with boiling significantly enhances the digestive characteristics of tilapia meat and the antioxidant activity of the digestion products, providing a theoretical basis for tilapia culture and processing.