Effect Of Ultrasound-assisted Freezing On The Storage Quality And The Protein Oxidation And Denaturation Of Sciaenops Ocellatus

Frozen storage is one of the common methods to maintain the quality of aquatic products,and the freezing method is the key factor to affect the quality of frozen products.The traditional freezing method s form irregular extracellular ice crystals in aquatic products,which can cause serious mechanical damage to the muscle tissue during the frozen storage.Meanwhile,oxidative denaturation of protein occurs,resulting in serious loss of water and quality degradation after thawing.Therefore,how to make the ice crystals distributed evenly in the frozen food by using the new freezing methods so as to improve the quality of prozen aquatic products has been a research hotspot.In this paper,compared with air freezing(AF)and immersion freezing(IF),the effects of ultrasound-assisted immersion freezing(UIF)under different power on freezing parameters,quality,microstructure,ice crystal morphology and protein oxidation of Sciaenops ocellatus were investigated.The objective of this study is to comprehend the influence mechanism of UIF technology on Sciaenops ocellatus's muscle quality during storage,and to provide reference for the further research and application of UIF technology in the field of aquatic products processing.The main findings of the study are as follows:1.Compared with IF,UIF can increase the nucleation temperature of the sample,and made it nucleat e in advance.The nucleation temperature of the sample was a linear function of the irradiation onset temperature of ultrasonic,with the regression equation of y=0.62x-2.02,and R²=0.9887.The nucleation temperature and freezing rate of the samples treated by UIF(0°C,200 W and 6 s/10 s)were 42.86%and 28.88%higher than those of IF group,respectively.In addition,the onset tempeature,ultrasound power and intermittent mode of UIF showed significant influences on the nucleation delay time,freezing time and freezing rate of Sciaenops ocellatus(P<0.05).2.Compared with AF,IF and UIF can significantly improve the freezing rate of Sciaenops ocellatus,and shorten the freezing time by more than 83%.Among them,the freezing rate of UIF-200W treated group was 712.81%,33.99%,27.11%and 54.09%higher than that of AF,IF,UIF-150W and UIF-250W groups,respectively.Meanwhile,the small and uniform ice crystals were formed in the samples of UIF-200W group,the degree of myofibril degradation was smaller,and the myofibrillar fragmentation index(MFI)were significantly lower than those of other groups(P<0.05).The water holding capacity(WHC)and texture characteristics of UIF-200W group were better than those of other groups during f rozen storage,while the degree of conversion from conbined water to free water was slighter than that of other groups.In addition,the whiteness and p H value were 9.19%and 5.02%lower than those of IF group(P<0.05),respectively.The thawing loss of UIF-250W group was 18.52%lower but the freezing rate was 13.04%lower than that of IF group,and the hardness of UIF-250W was significantly lower than that of IF group(P<0.05).3.After 90 days of frozen storage,the content of total sulfhydryl and active sulfhydryl,protein solubility,Ca²⁺-ATPase activity and?-helix percentage of myofibrillar protein(MP)of the samples of UIF-200W group were 7.95%,27.20%,11.10%,40.86%and 1.92%higher than those of IF group,while the content of carbonyl and surface hydrophobicity were 30.38%and 28.86%lower than that of IF group,indicating that the oxidative denaturation of myofibrillar prote in of the samples of UIF-200W group had been slowed down.Moreover,the DSC analysis results showed that the frozen samples of UIF-200W group had higher protein stability than that of other groups.However,UIF-250W treatment promoted protein oxidation and destroyed the functional properties of myofibrillar protein.4.In summary,freezing under appropriate ultrasonic power(200 W)can help the samples pass through the maximum ice crystal generation zone quickly,improv e the freezing rate,and reduce the irreversible mechanical damage caused by ice crystal.Furthermore,the quality deterioration of frozen samples was slight during frozen storage,and the oxidative denaturation of myofibrillar protein was effectively inhibited.However,although the high ultrasonic power(250 W)can reduce the water fluidity and thawing loss of the samples,and improve the water holding capacity,it also can destroye the integrity of myofibril,change the conformation of myofibril protein,and promote the oxidation of myofibril protein.