This study addressed the effect of ultra-high pressure (UHP) versus irradiation sterilization on the shelf life and quality of largemouth bass. After being treated by UHP at 200 MPa or electron beam irradiation at 1.5 kGy, the fish were stored under vacuum at 4 ℃ and evaluated for total bacterial count (TBC), total volatile basic nitrogen (TVB-N) content, thiobarbituric acid reactive substances (TBARs) value, color, pH, juice loss, hardness, texture properties and water distribution. The results showed that the increase of TBC, TVB-N content and TBARs value was significantly inhibited by UHP and irradiation treatments, and the irradiation treatment better delayed the spoilage of fish. The TBC in the blank and UHP groups exceeded the national standard limit after 9 d. Moreover, at this time point, the TVB-N content in the blank group also exceeded the national standard limit, while the UHP group did so after 12 d. The pH of all treatment groups showed a decreasing trend during the storage period. The UHP treatment increased the whiteness and loosened the structure of fish meat. Irradiation decreased the whiteness and the moisture content. The storage period of fish meat was significantly prolonged by both UHP and irradiation treatments, and the inhibitory effect of irradiation was better than that of UHP with less impact on fish meat quality.

Chitosan nanoparticle is becoming an excellent carrier for the delivery of bioactive components due to the advantages of simple preparation, low cost and high biocompatibility. Previous studies have shown that chitosan/sodium tripolyphosphate (CS/TPP) and chitosan/flaxseed gum (CS/FG) nanoparticles loaded with bighead carp peptides (BCP) have the advantages of small particle size, high encapsulation rate and significant slow-release effect. This study explored the effects of ionic strength, pH, simulated digestion and storage time on the preparation of chitosan/sodium tripolyphosphate (CS/TPP-BCP) and chitosan/flaxseed gum (CS/FG-BCP) nanoparticles, and evaluated the extracellular lactate dehydrogenase content and antioxidant capacity in vivo of Caco-2 cells treated with the chitosan nanoparticles and their cellular uptake. The results showed that the two kinds of chitosan nanoparticles were stable under acidic conditions and sensitive to a solution with opposite charges. The stability of the nanoparticles loaded with bighead peptides was higher than that of free peptides and both nanoparticles showed higher biocompatibility and cell uptake.