Effect Of Repeated Freeze-thaw Cycles On Sensory Quality And Water Retention Of Cooked Crayfish And Its Improvement Methods

With its unique flavor,tasty meat and high protein and low fat characteristics,crayfish is loved by different groups of people.With the upgrading of consumption and advances in cold chain logistics and transportation technology,major brands have launched online e-commerce platforms,and crayfish pre-prepared dishes are gradually entering the mainstream food and beverage market and becoming popular with end consumers.However,the high protein and moisture content of crayfish makes them susceptible to spoilage by oxidation reactions,microorganisms and endogenous enzymes,leading to a decline in their quality and economic value.This paper investigated the changes in sensory quality and water retention of cooked crayfish during repeated freeze-thaw cycles and the effects of ultrasound-assisted alginate oligosaccharide soaking on cooked crayfish after repeated freeze-thaw cycles,with a view to elucidating the changes that occur during repeated freeze-thaw cycles of cooked crayfish and providing a theoretical basis for the production and marketing process of cooked crayfish.The main findings and conclusions of the study are as follows.(1)The effect of freeze-thaw cycles(a freeze-thaw cycle consisting of storing crayfish at-20 °C for 12 h followed by thawing at 4 °C for 3 h,with freeze-thaw cycles of 0,1,2 and 5)on the quality of cooked crayfish was investigated,with significant changes in the quality of cooked crayfish: a decrease in moisture content,water-holding capacity,p H and textural properties,and a significant increase in total color difference and LF-NMR and MRI confirmed that repeated freezethaw cycles increased the moisture loss of cooked crayfish;the significant increase in TVB-N and TBARS values indicated that the freeze-thawing cycle increased protein oxidation and lipid oxidation in cooked crayfish(p < 0.05).(2)Using cooked crayfish as an object of study,significant structural changes in cooked crayfish were investigated during the freeze-thaw cycles: SEM results showed that repeated freezethaw exacerbated the destruction of the microstructure of cooked crayfish muscle fibers;SDSPAGE showed that freeze-thaw cycles exacerbated the denaturation or degradation of cooked crayfish myogenic fibrillar proteins(MPs);multiple freeze-thaw cycles promoted the secondary structure from The change in MPs’ conformation was confirmed by changes in the content of MPs’ chemical bonds(ionic,hydrogen,hydrophobic interactions and disulfide bonds),as evidenced by the gradual decrease in endogenous fluorescence intensity.Repeated freeze-thaw cycles reduced the water content in cooked crayfish and changed the structure of MPs,resulting in the destruction of their physicochemical properties and structure.(3)The effect of ultrasound(40 W,3 min)assisted alginate oligosaccharide(1%,w/v)soaking(AUS)on the water retention of cooked crayfish after repeated freeze-thaw cycles was investigated using cooked crayfish,and the results showed that AUS improved the water holding capacity,color and textural properties of cooked crayfish after repeated freeze-thaw cycles and reduced water loss.Also,the microstructure of cooked crayfish was better maintained after AUS treatment,with a smaller area and number of ice crystals in the tissues.In addition,the AUS MPs had higher solubility and zeta potential,lower surface hydrophobicity and particle size,indicating high secondary and tertiary structural stability of MPs after repeated freeze-thaw cycles on cooked crayfish.SDS-PAGE further verified that AUS inhibited the partial degradation or denaturation of MPs.These results demonstrated the mechanism of action of AUS treatment for improving water retention in crayfish cooked after repeated freeze-thawing.Repeated freeze-thaw cycles reduced the moisture content of cooked crayfish and changed the structure of MPs,resulting in the destruction of their physicochemical properties and structure.The water retention of cooked crayfish after repeated freeze-thaw cycles was improved by ultrasound-assisted alginate oligosaccharide soaking,which effectively improved the sensory quality of the crayfish.