Ultrasound treatment of frozen crayfish with chitosan Nano-composite water-retaining agent: Influence on cryopreservation and storage qualities.

The synergistic impact of ultrasound and Nano-water retaining agent on the cryoprotective effect on crayfish during frozen storage was investigated. The samples soaked in water-retaining agent (WRA), ultrasonic 60 W treatment combined with water-retaining agent (WRA-US60W) and ultrasonic 80 W treatment combined with water-retaining agent (WRA-US80W) were frozen storage at -18 °C. The indices of frozen storage in 0, 7, 14, 21, 28, 35 and 42 days were measured. The results showed that there was a significant difference in the soaking weight gain, thawing loss, water content and water activity between control group and WRA groups (P < .05). The ultrasound combined with WRA treatment showed better water retention effect. The water holding capacity of heat induced gel decreased continuously during the frozen storage period, and the WRA-US60W group exhibited significantly higher values than that of other treatment groups (P < .05). The texture characteristics of hardness, elasticity and chewiness had a significant change (P < .05). The development of total volatile base nitrogen content, myofibrillar protein content and Ca2+-ATPase activity of muscle protein were significantly delayed by WRA-US60W treatment, maintaining the integrity of tissue structure. Therefore, WRA-US60W treatment was found effectively improving the quality of crayfish during frozen storage.