Synergistic Effects Of Soluble Soybean Polysaccharide And Ultrasound On Frozen Surimi From Grass Carp

Cryopreservation is a method of long-term preservation of surimi products.During the process of cryopreservation,myofibrillar proteins are easily denatured,decreasing in the processing characteristics of surimi and surimi products.In this study,soluble soybean polysaccharides?SSPS?was used as a cryoprotectant,and ultrasound-assisted immersion freezing?UF?was used to freeze surimi.The effects of two factors on the freezing process and product quality of surimi were explored.New ideas and new methods were provided to freeze surimi and surimi products,expanding the application of SSPS in the field of aquatic product processing.The main findings were as follows:?1?To study the effect of ultrasonic power,exposure time,interval time and ultrasonic frequency on UF,according to the characteristic freezing time,tempering stage freezing rate and the change of frozen product quality,comprehensive analyzed the optimal ultrasonic parameters of UF processing.The optimal parameters were:ultrasonic power 300 W,ultrasonic exposure time 10 s,ultrasonic interval time 40 s and ultrasonic frequency 5 times.?2?The characteristic freezing time of surimi by immersion freezing?IF?with adding 1%,3%and 5%SSPS increased by 3.06%,6.93%and 1.06%,respectively,as compared without adding SSPS.To determine the index of protein denaturation of frozen surimi after 8-week frozen storage,compared to the initial value,the total sulphydryl content of grass carp surimi myofibrillar protein decreased by 57.05%,47.20%,42.11%and 44.65%after 8-week frozen storage,respectively.The salt extractable protein content of grass carp surimi myofibrillar protein decreased by78.27%,67.85%,60.92%and 64.24%,respectively.By high performance gel permeation chromatography?GPC?analyzed,the peak relative molecular weight Mp of SSPS was 655751 Da,the weight average relative molecular weight Mw was410113 Da,and the number average relative molecular weight Mn was 32244 Da.By Fourier transform infrared spectroscopy?FTIR?analyzed,SSPS had an absorption peak at 3393 cm^-1 due to-OH vibration.Since the hydroxyl groups in the SSPS molecules were cross-linked with the N-H of the surimi protein,the 1033 cm^-1absorption peak changes significantly.The results of the study showed that SSPS could delay protein degeneration during storage at-18^oC,and 3%?w/w?SSPS could effectively mitigate the protein denaturation of grass carp surimi.?3?The characteristic freeze time of surimi by UF freezing method adding with1%,3%and 5%SSPS increased by 5.94%,13.93%and 8.96%,respectively,as compared without adding SSPS.To determine the index of protein denaturation of frozen surimi after 8-week frozen storage,compared to the initial value,the total sulphydryl content of grass carp surimi myofibrillar protein decreased by 51.44%,39.56%,34.13%and 37.01%after 8-week frozen storage,respectively.The salt extractable protein content of grass carp surimi myofibrillar protein decreased by74.62%,63.32%,54.15%and 60.44%,respectively.The results showed that SSPS had positive effects on myofibrillar protein of surimi.Consequently 3%SSPS was best for synergistically mitigating the protein denaturation of frozen surimi by UF.?4?After the UF treatment,the characteristic freeze time of surimi adding with 3%SSPS,SSPS composite cryoprotectant and commercial cryoprotectant?sucrose,sorbitol?increased by 26.20%,28.48%and 31.34%,respectively,as compared with adding commercial cryoprotectant by IF.To determine the index of protein denaturation of frozen surimi after 8-week frozen storage,compared to the initial value,the total sulphydryl content of grass carp surimi myofibrillar protein decreased by 34.13%,25.13%,23.09%and 24.45%,respectively.The salt extractable protein content of grass carp surimi myofibrillar protein decreased by 54.15%,39.63%,37.45%and 38.81%,respectively.The results showed that the effect of adding commercial cryoprotectant to the three surimi samples by UF was the best,and the effect of adding SSPS composite cryoprotectant was second.