Structural Changes And Properties Of Loach Myofibrillar Protein

In this study,we extracted myofibrillar protein from loach to study the structural changes of loach myofibrillar protein under different levels of cassava starch and cassava acetate starch,and the effect of different environmental conditions on the properties of loach myofibrillar protein.It provides theoretical support for improving the quality of loach surimi products,and finds some new approaches to the application of starch and the production,processing and development of related products.The research results are as follows:The basic components of loach meat:water(74.53%),protein(17.72%),crude fat(3.66%)and ash(1.30%).The isoelectric point of myofibrillar protein was 5.0.Myofibrillar protein was mainly composed of myosin,actin and some small molecules,and myosin was the main component.With the increase of cassava starch and cassava acetate starch,the UV absorption intensity of loach myofibrillar protein increased gradually and the maximum absorption peak at 280 nm shifted red;the UV absorption of cassava acetate starch was higher than that of cassava starch under the same dosage.It can be seen from the Raman spectrum that with the addition of starch,the disulfide bond of protein reduced;with the increase level of the starch,tryptophan tended to be "embedded state",the content of α-helix decreased,the content of βfold increased,the content of β-angle and irregular curl changed not obviously,and it was not related to the type of starch.With the increase of starch,the median diameter of the system gradually increased,and it formed large,agglomerated aggregates gradually;moreover,the median diameter of cassava acetate starch group was larger,and the cross-linking and aggregation was more obvious.Electron microscopy figured out that the myofibrillar protein showed a loose and irregular network structure.The starch could effectively fill the pores,and the more the amount of the starch,the denser the gel was.The structure of the gel added with cassava acetate starch was more uniform and smooth than that of cassava starch under the same starch level.The effect of cassava acetate starch on gel hardness,water holding capacity,springiness and whiteness of cassava starch was higher than that of cassava starch under the same level.With the increase of starch content,the hardness and water holding capacity of myofibrillar protein gel rose,the whiteness declined,and the springiness increased first and then decreased.With the increase of temperature,the absorbency of myofibrillar protein first went up to the peak at 50℃,and then went down;the oil absorption gradually decreased;foaming at 60℃ was the best,and the foam stability gradually fell;the hydrophobicity and turbidity of the myofibrillar protein rose gradually,and reached the peak at 80℃.With the increase of pH,the absorbency and foaming ability of myofibrillar protein were the highest at pH 7.0;the foam stability increased slightly;the hydrophobicity of myofibrillar protein first increased and then decreased,when pH was 5.5 it reached the maximum;and the turbidity of myofibrillar protein gradually declined.With the increasing concentration of myofibrillar protein,the absorbency increased first and then decreased;the foaming and hydrophobicity went up first and then went down,which was the highest at 2 mg/mL;and the foam stability decreased not significantly;turbidity increased significantly,and reached the maximum at 5mg/mL.