Our aim was to study the effect of phenyllactic acid treatment on the quality of channel catfish during low temperature storage. Channel catfish was treated with phenyllactic acid (0.5, 1.5 or 2.5 g/100 mL) and stored at 4 ℃. The changes of total bacterial count (TBC), total volatile basic nitrogen (TVB-N) content, thiobarbituric acid reactive substances (TBARs) value, water-holding capacity (WHC), texture, color and sensory quality were analyzed. It was found that TBC, TVB-N content and TBARs value of channel catfish treated with phenyllactic acid were significantly lower than those of the control group, indicating that phenyllactic acid preserves the quality of channel catfish; the most pronounced effect was observed at 2.5 g/100 mL, but compared with the other concentration groups, little differences were found in pH, WHC, color and texture. In general, treatment with 2.5 g/100 mL phenyllactic acid can significantly prolong the shelf life of channel catfish during low temperature storage while having little effect on its physicochemical properties and sensory evaluation.

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.

In order to explore the effect of irradiation dose on the quality and flavor of crayfish roe from crayfish processing wastewater, changes in safety indexes such as total bacterial count, coliform group, and heavy metal content were analyzed after ⁶⁰Co-γ ray irradiation at different doses (2, 4, 6, and 8 kGy). Meanwhile, the flavor characteristics were evaluated by the combined use of electronic nose and gas chromatography-mass spectrometry (GC-MS). The results showed that irradiation doses ≥ 4 kGy had better inhibitory effects on the total bacterial count and coliform group, and the heavy metal content in the treated sample met the national standard. The results from the electronic nose showed significant differences in the flavor of crayfish roe treated with four different irradiation doses, and the response values for nitrogen-containing oxides and sulfur-containing compounds increased with irradiation dose. The sample treated with a dose of 6 kGy had the highest amount of volatile flavor compounds (19), the predominant ones being aldehydes, alcohols, and heterocycles. The 4 and 6 kGy irradiation groups were more acceptable in sensory evaluation. In general, 6 kGy irradiation was superior to the other doses in terms of safety and flavor.

We performed this study in order to investigate the effect of ultrasound (US) and ultra-high pressure (UHP) treatments on the flavor-binding capacity of proteins from the perspective of its structural alteration. Hexanal, 1-octen-3-ol, or 3-methylbutyraldehyde was added to myofibrillar protein (MP) extracted from topmouth bleak (Culter alburnus) before being treated by US (200 and 300 W) or UHP (100 and 250 MPa) for 15 min. After the treatments, the changes in volatile compound concentrations were measured to verify the effect of protein structural alteration on its flavor-binding capacity. The results showed that different treatments affected the binding capacity of fish MP to flavor substances. Both US and UHP treatments substantially increased the hexanal-binding capacity of MP, but slightly decreased the 3-methylbutyraldehyde-binding capacity of MP, and decreased the 1-octen-3-ol-binding capacity of MP to 24%-35%. Among all the treatments tested, UHP treatment at 100 MPa had the greatest effect on the flavor-binding capacity of MP. Both treatments affected the free and total sulfhydryl content and surface hydrophobicity of MP, and increased the maximum fluorescence intensity and ultraviolet (UV) absorption intensity, with the increase being more pronounced upon addition of volatile compounds. In conclusion, US and UHP treatments can effectively change MP structure, thereby being conducive to the flavor-binding ability of fish.

In order to fully utilize crayfish shell, fermented crayfish paste added with different amounts of crayfish shell powder (0%, 20%, and 40%) was evaluated at different fermentation times for free amino acids, taste nucleotides, organic acids and sensory quality. The relative taste activity value (RTAV) was calculated to determine major taste contributors. The results showed that fermentation time had little effect on the total free amino acids (TFAAs) content of fermented crayfish paste with 0 and 20% crayfish shell powder. Fermented crayfish paste with 20% crayfish shell powder had a more obvious umami taste. The TFAAs content of fermented crayfish paste with 20% crayfish shell powder changed mainly in the early period of fermentation, decreasing significantly, and addition of 20% crayfish shell powder inhibited the bitterness of crayfish paste more significantly. Based on RTAV and variable importance in projection (VIP) scores, potential differential compounds affecting the taste were selected, and the taste substances Ile, GMP, Ala, Val, Leu, IMP, Glu, Asp, Cys, and His played a dominant role in the formation of the taste of crayfish paste. By combining the above results with sensory analysis, we concluded that addition of crayfish shell powder had a significant effect on the flavor of fermented crayfish paste. This study provides a theoretical basis for understanding the effect of addition of crayfish shell powder on the flavor of fermented crayfish paste.