Effects Of Freezing And Thawing Methods On Myofibrillar Protein And Quality Of Large Yellow Croaker(pseudosciaena Crocea)

The meat of the large yellow croaker is delicious,with high protein content and rich in monounsaturated fatty acids.It is one of the important marine economic fishes in China,and its aquaculture production ranks first in the world.At present,the consumption of large yellow croakers in China is mainly defrosted"fresh fish"and dried salted yellow croaker.However,the optimization of different culture modes of the large yellow croaker,the process of"freeze to-fresh"and the improvement of quality are one of urgent problems for the large yellow croaker industry.Therefore,it is necessary to improve its freezing and thawing treatment technology,which is conducive to improving the quality of large yellow croaker.Since myofibrillar protein is the main component that affects the quality of frozen fish meat,if the protein freeze-denaturation occurs during frozen storage,the quality of large yellow croakers will be greatly affected.After thawing,the change of skin color and the loss of water of the large yellow croaker will have a negative impact on the quality.Therefore,this paper analyzes and compares the protein characteristics of large yellow croakers with the two culture modes,studies the effects of the addition of antifreeze polysaccharides from flammulina velutipes,two freezing methods,and different thawing methods on the quality of large yellow croakers.Firstly,the rheological characteristics of myofibrillar protein in large yellow croakers were studied.Taking fresh large yellow croaker as the object,the rheological characteristics of myofibrillar protein in large yellow croakers under two culture modes?through-frame cage and purse seine culture?were explored through small-amplitude and large-amplitude oscillating shear rheology.The results show that during the temperature scan,the elastic modulus?G'?gradually increases with the increase of temperature,and does not decrease during the gel weakening stage at 45?55?,only slows the rate of increasing,and in the gel strengthening phase,the G'of the large yellow croaker from seine culture mode is much larger than that of the large yellow croaker in the through-frame culture mode.In the dynamic strain scan,frequency scan and viscosity test,it can also be seen that the G'value of myofibrillar protein of seine culture mode is relatively high.The large-amplitude oscillating shear test showed that the network structure of the myofibrillar protein of large yellow croaker was tighter and the energy for one cycle of shearing was greater.Secondly,the effects of different freezing methods on the physical and chemical properties of myofibrillar protein in large yellow croakers were studied with the addition of antifreeze polysaccharides.In order to study the frozen degeneration of myofibrillar protein in frozen yellow croakers,the large yellow croakers treated with antifreeze polysaccharide concentrations?0 mg/m L,0.0625 mg/m L,0.125 mg/m L and 0.25 mg/m L?were analyzed.Liquid nitrogen frozen quick-freeze and refrigerator-frozen frozen yellow croakers treated with total sulphydryl content of myofibrillar protein,Ca²⁺-ATPase activity and temperature scanning,and ice crystal growth of myofibrillar protein with antifreeze polysaccharides added.The results showed that the antifreeze polysaccharide can inhibit the growth of ice crystals,and the higher the concentration,the more obvious it is.The total sulphydryl content and Ca²⁺-ATPase activity of myofibrillar protein in the 0.0625mg/m L antifreeze polysaccharide croaker group were higher than those in other concentration groups.And the G'is the highest during the temperature scanning,which indicates that the antifreeze polysaccharide has a freezing protection effect on the yellow croaker;under the two freezing methods,the time taken by the liquid nitrogen freezing group to pass the maximum ice crystal formation band is significantly shorter than the refrigerator freezing group,which is fast freezing.During frozen storage,the total sulphydryl content and Ca²⁺-ATPase activity of the myofibrillar protein of the yellow croaker was higher than that of the refrigerator freezing group,and the G'value in the rheology chart was also higher than that of the refrigerator freezing group.Freezing denaturation has a certain inhibitory effect.Finally,the effects of different thawing methods on the quality and water migration of croakers were studied.The results showed that after thawing,the b*value of large yellow croaker showed a decreasing trend,and the yellow-blue value was decreasing,while the large yellow croaker of the radio frequency thawing group had higher b*value than that of ice-thawing and flow-thawing.The surfacehydrophobicity of croaker myofibrillar protein increased and the total sulphydryl content decreased.The surface hydrophobicity of myofibrillar protein of croaker after radio frequency thawing was low.In the other two thawing methods,the total sulphydryl content was higher than the other two thawing methods.Low-field nuclear magnetic resonance was used to measure the distribution of water.According to the table drawn based on the proportion of peak area obtained by the inversion software,it can be seen that with the extension of time,the immovable water is gradually reduced,the free water is gradually increased,and the RF thawing group is not available.Moving water is higher than other thawing groups,and free water is lower than other thawing groups.This shows that large yellow croakers with RF thawing have better water retention capacity than the other two groups and delay the decline of quality.