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.

In order to investigate the effect of arginine (Arg) on the microwave-induced pre-gelation of myofibrillar protein (MP) from sturgeon under low salt condition, MP added with different concentrations of Arg was microwaved and evaluated for physicochemical, structural and morphological properties and intermolecular interactions after 1, 3 and 5 min (< 40 ℃). It was found that the solubility of MP decreased with increasing microwaving time and was improved by appropriate concentrations of Arg (P < 0.05). The turbidity of MP microwaved for 5 min significantly decreased with increasing addition of Arg (P < 0.05). The particle size decreased with increasing levels of Arg addition. In addition, Arg inhibited the formation of large protein clusters during microwave heating as shown by atomic force microscopy. In the control group, the contents of ionic and hydrogen bonds decreased significantly after microwave treatment for 3 min, while the contents of hydrophobic interaction and disulfide bond increased significantly (P < 0.05). The addition of 40 mmol/L Arg inhibited the ionic bond and hydrophobic interaction and increased the hydrogen and disulfide bonds. The molecular dynamics simulation results showed that at 300 K, the root mean square deviation (RMSD) for myosin increased from about 0.52 to 5.85 nm after Arg binding to it, and the radius of gyration (R_g) also increased, indicating that Arg promoted the dissociation of MP aggregates under low salt condition, and the aggregate characteristics changed from larger protein clusters to smaller particles. Furthermore, binding of Arg to myosin decreased its structural tightness, resulting in more loose protein conformation. The findings of this study provide sufficient conditions for enhancing protein cross-linking in the gel strengthening stage.

The sensitivity of freshness indicator labels/films has become an important research direction of intelligent food packaging. In this study, a high-sensitivity indicator film containing gelatin and Fe²⁺ was prepared by electrospinning using blueberry anthocyanins as the indicator and zein as the matrix for monitoring fish freshness. The validity and sensitivity of the indicator film for detecting the freshness of silver carp were tested and the potential mechanism was elucidated. The results of pH sensitivity, ammonia sensitivity and anthocyanin release showed that the addition of gelatin and Fe²⁺ improved the sensitivity of the indicator film to pH and ammonia, and contributed to better binding of the anthocyanins in the film. There was a strong correlation between the color response (P = (L* + a* + b* + R + G + B)/a*) of the film and the content of total volatile basic nitrogen (TVB-N) content in fish meat as a freshness indicator (R² > 0.98). In conclusion, the prepared indicator film can effectively monitor fish freshness, and the hydrogen bond interactions between anthocyanins and gelatin/Fe²⁺ may affect the color response characteristics and sensitivity of the indicator film.

The addition of oil played a significant role in the gelling properties and flavor qualities of the ready-to-eat surimi gels. In order to investigate the effects of sturgeon oil and reheating methods on the qualities of sturgeon surimi gels, the prepared sturgeon surimi gels containing sturgeon oil (with the direct addition named SO and with the Pickering emulsion named PPE) were reheated by boiling, steaming, microwave, and frying, respectively. The gel properties, non-volatile and volatile flavor substances and digestibility were determined. Boiling and steaming made gels higher brightness value (L*) (82.07–84.16), with lower cooking loss (7.11%–8.83%), relatively intact protein network structures and strong protein digestibility. The greatest lipid oxidation of the sturgeon surimi gels was induced by frying, followed by microwave. Furthermore, the gels reheated by microwave showed the highest total flavor-presenting nucleotides, while the steamed ones had the highest total percentage of fresh and sweet amino acids. The addition of sturgeon oil (direct addition and Pickering emulsion) decreased the textural properties of the reheated gels, but significantly improved the L* and protein digestibility of boiled and steamed gels (P < 0.05). The gastric digestibility and gastrointestinal digestibility of the SO and PPE groups were 68.60%–76.33% and 80.69%–85.05%. Moreover, the addition of sturgeon oil also changed the ratio of non-volatile and volatile flavor compounds. Compared with the direct addition of sturgeon oil, the preparative Pickering emulsion was more conducive to the retention of better textural properties as well as the more flavor-presenting nucleotides and volatile flavor substances. The above results enrich the theory of quality difference of sturgeon surimi products caused by different reheating methods, and provide reference for the development of high-quality products.