Study On The Structure And Functional Properties Of Molten Globule Soybean 11S Protein Induced By Heat Treatment

In recent years,soybean protein has good nutritional and functional properties.Due to the easy aggregation,insoluble,and instability of soy protein during processing,the utilization rate of soy 11S globulin is reduced,which greatly limits the development of soy products.Therefore,how to regulate so that soybean 11S globulin can be better used in processing is a crucial issue at present?Molten globule state protein is an intermediate protein with better functional properties.It has good foaming,emulsification and biological activity.However,it is still unclear how the thermal stability of the molten globular protein soy 11S globulin is?Therefore,this experiment uses soybean 11S globulin as the main raw material,and uses untreated soybean 11S globulin as a natural state and a completely denatured state induced by 6 mol/L guanidine hydrochloride as a control.Soybean 11S globulin was heated at 90,100 and 120? for 1,2,3,4,5,10,15,30 and 60 min respectively to induce unfolding.The formation process of soybean 11S globulin was described by secondary structure,tertiary structure,surface hydrophobicity and particle size.The obtained molten soybean 11S globulin was heated in 75? and 100? water bath for 30 min and 20 min respectively to observe its thermal stability.The functionality of 11S globulin was evaluated by the determination of emulsifying property,emulsifying stability,foaming property and foaming stability,which provided a theoretical basis for the good application of 11S globulin in food processing.The main results are as follows:(1)By circular dichroism(far/near UV),fluorescence spectrum(internal fluorescence/external fluorescence)and average particle size determination,the formation conditions of molten soybean 11S globulin under heat treatment were obtained.Heat treatment at 100? for 3 min.At this time,the rigid tertiary structure of soybean 11S globulin basically disappeared,and it had a secondary structure similar to that of natural soybean 11S globulin,with greater endogenous fluorescence intensity and larger hydrophobic surface area.At this time,the average particle size of soybean 11S globulin increased by 1.8 times compared with that of natural soybean 11S globulin,but it still had a similar tightness to that of natural soybean 11S globulin.(2)Through the determination of SDS-PAGE gel electrophoresis,average particle size,zeta potential,turbidity and Mercapto content,the 11S globulin samples of 1-60 min heated at 100? were analyzed.It was found that the globular structure of soybean globulin was formed at 100? heat treatment.The results show us the more detailed heat change process of 11S globulin in 100?.The results show that the fusion globulin is a kind of protein with good heat stability and is more suitable for food processing.(3)The surface tension,molecular flexibility,emulsifying activity,emulsifying stability,foaming and foaming stability of soybean 11S globulin in natural and molten globules were measured respectively.The microstructure of molten globule protein emulsion and bubbles was observed by confocal scanning electron microscope and freeze scanning electron microscope respectively.The surface tension of molten soybean 11S globulin decreased to 66.22 × 10-3 N/m,both emulsifying and foaming properties were improved.The droplet surface of the globule soybean 11S globulin was more smooth,and more protein granules were adsorbed on the interface,so that the emulsion stability was improved.A layer of protein molecule adsorption film with a certain thickness and orderly arrangement can be formed on the surface of bubbles formed by molten soybean 11S globulin,which makes the foaming stability better improved.The formation,capture,thermal stability and functional properties of soybean 11S globulin were studied by heat treatment induction method,which enriched the technical means,structural characterization analysis and mechanism research of the structure formation of soybean 11S globulin,provided basic data for the application of soybean 11S globulin,and further improved the application value of soybean protein.