Effects Of Mannooligosaccharide And Curdlan On Freeze-thaw Stability Of Freshwater Surimi

Surimi is a protein-rich food material that is highly susceptible to spoilage and is commonly stored and transported frozen.However,during cryopreservation,it tends to cause protein denaturation,which reduces the processing quality of surimi.Currently a 4%sucrose and 4%sorbitol mixture were commonly used as a commercial antifreeze to inhibit protein denaturation in frozen surimi.However,the high calorie and sweetness of commercial antifreeze cannot satisfy people’s pursuit of health.Therefore,this paper firstly investigated the effect of mannan oligosaccharides and curdlan on the freeze-thaw stability of freshwater surimi,and then optimized the ratio of mannan oligosaccharides and curdlan using a central combined response surface test and conducted validation experiments,aiming to develop a new low-sweetness and lowcalorie compound antifreeze agent for the freeze-thaw preservation of surimi.The main findings of the study were as follows:The effects of different additions of mannan oligosaccharides on the hydration properties,gelation properties and protein structure of surimi during the freeze-thaw cycle were investigated.The results showed that the addition of 8%mannan oligosaccharides decreased the freezing point of surimi by 1.3 ℃,reduced the time to pass through the maximum ice crystal zone by 6 min and slowed down the ice crystal growth rate,thus reducing freezing damage and protein denaturation of surimi compared with the blank control group.After 7 freeze-thaw cycles,the 8%mannan oligosaccharide surimi effectively slowed down the growth of thawing losses,the decrease in gel strength,gel water holding capacity and gel colour,the decrease in saltsoluble protein content,sulfhydryl and active sulfhydryl groups and α-helical structure,and the growth of hydrophobicity on the surimi surface compared to the blank control group.The antifreeze effect of 8%mannan oligosaccharides was comparable to that of commercial antifreeze agents during the first five freeze-thaw cycles,but after the seventh freeze-thaw cycle,the antifreeze effect of 8%mannan oligosaccharides was better than that of the commercial antifreeze group.The effects of supplemental addition of 0%-1%curdlan at 4%mannan oligosaccharide on the thawing loss and gelation characteristics of surimi during freezethaw cycles were investigated.The results showed that after five freeze-thaw cycles,the thawing losses of the commercial antifreeze group and the 4%mannan oligosaccharide supplemented with 0.2%～0.6%curdlan group increased by 4.21%,6.25%,13.01%and 4.13%respectively,the gel strength decreased by 18.97%,15.47%,20.17%and 23.29%,the hardness decreased by 7.49%,4.50%,13.47%,21.96%,water holding capacity decreased by 5.50%,4.37%,8.75%,10.10%respectively.Therefore,the combination of 4%mannan oligosaccharide and 0.2%～0.6%curdlan had a better anti-freezing effect on the gel of surimi.The central combined response surface test was used to optimize the gel strength and thawing loss rate of surimi for 5 freeze-thaw cycles,and the optimal ratio of 6.79%mannan oligosaccharide and 0.45%curdlan was obtained.The results of the validation experiments showed that the relative errors between the predicted and real values of gel strength and thawing loss were 0.73%and 4.49%respectively.The addition of the compound antifreeze to each 100g of surimi resulted in a 131.81 kJ decrease in heat compared to commercial antifreeze,making it a low calorie of surimi antifreeze.The effect of 6.79%mannan oligosaccharide and 0.45%curdlan complex antifreeze on the freeze-thaw stability of surimi during seven freeze-thaw cycles was investigated using a blank control and a commercial antifreeze as a control.The results showed that after seven freeze-thaw cycles,the combined group of 6.79%mannan oligosaccharide and 0.45%curdlan,the control group and the commercial antifreeze group showed a decrease of 4.68%,22.78%and 14.71%in bound water content,6.46%,14.81%and 10.67%in gel water holding capacity,59.44%,86.83%and 56.54%in saltsoluble protein content,and the total sulfhydryl content decreased by 63.42%,84.55%,73.11%and the tryptophan fluorescence intensity decreased by 23.83%,30.84%,23.21%.The combination of 6.79%mannan oligosaccharides and 0.45%curdlan was effective in slowing down the rate of decrease in bound water content,gel properties and protein denaturation of surimi during the freeze-thaw cycle,and in enhancing the freeze-thaw stability of surimi.