Study On Fat Mimics Made Of Soy Protein Isolates Hydrolysates-Polysaccharide Complex Substance

With the continuous improvement of people’s living standards,high-fat and high-heat food is more and more popular in daily diet because of its unique flavor and taste.However,excessive fat intake brings a series of disease risks such as hypertension,hyperglycemia and hyperlipidemia.Fat replacer uses protein and carbohydrate as matrix,and carries on certain physical and chemical treatment to achieve the purpose of simulating the delicate lubrication taste of fat.In present study,SPI was modified by alkaline protease.In addition,by adding polysaccharides to further modify the SPH,a compound fat replacer was prepared and applied to the development of cream-mimics,thus providing a theoretical basis for the development and utilization of compound fat in cream processing.Alkaline protease was used to restrict the enzymatic hydrolysis of SPI by 1%-6%,and the structural changes of SPH were studied by Sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE),Fourier transformed infrared spectroscopy(FTIR),Scanning electron microscopy(SEM)and Laser particle size distribution instrument.The variation of molecular weight showed that the 7S globulin with high molecular weight was first destroyed by alkaline protease during initial hydrolysis.With the increased of hydrolysis degree(DH),both 7S and 11S globulins were destroyed.When the DH was 6%.the molecular weight of 7S globulin was mostly concentrated below 10 kDa.The hydrophobicity of SPH increased firstly and then decreased,and the hydrophobicity of SPH increased twice as much as that of SPI when the DH was 2%.Besides,hydrolysis significantly reduced the content of β-folding and β-corner structure,and increased the content of irregular crimp structure.When the degree of enzymatic hydrolysis reached 6%,the content of α-helix and β-corner increased obviously,while the content of β-fold and irregular curl structure decreased.The particle sizes distribution before and after enzymatic hydrolysis was characterized.The particle sizes of proteins before and after hydrolysis were characterized.The results showed that the limited hydrolysis process significantly reduced the particle sizes of proteins in SPI solution.The particle sizes of proteins after enzymatic hydrolysis were mainly distributed in a bimodal state,and the main peaks were near 0.7 and 20 microns.At the same time,with the increase of hydrolysis degree,the main peak of large particle size decreased and the content of small particle size increased.When the DH was 6%,the main peak of large particle size increased.The surface characteristics of proteins before and after hydrolysis were observed by SEM.It was found that obvious aggregation occurred at 6%DH.The processing characteristics of SPH were observed.With the increase of hydrolysis degree,the emulsifying activity of SPH changed significantly,which increased first,then decreased and then increased.The emulsifying activity of SPH was higher than that of SPI only at 1%and 2%hydrolysis degree.However,compared to the SPI,hydrolysis made the emulsion stability of SPH significantly improved,when the hydrolysis degree is higher than 2%,the emulsion stability began to decline,and began to pick up in 6%DH.At the same time,the foaming experiments showed that hydrolysis significantly improved the foaming property of SPI,which showed a trend of increasing first and then decreasing,and had the highest foaming property at 3%hydrolysis degree.The changes of foaming stability indicated that the foaming stability after hydrolysis decreased to a certain extent.Because the small molecular peptide segment could not maintain the air wrapped in liquid membrane,it showed the worst foaming stability at 5%DH.In addition,hydrolysis may produce a series of bioactive peptides.Therefore,the free radical scavenging capacity of SPH was determined.The results showed that the free radical scavenging rate of SPH increased gradually with the increase of DH.In 5 mg/mL protein solution,the free radical scavenging rate of SPH was the highest(55.87%)at 6%DH,which could produce free radical scavenging effect similar to that of 6 ug/mL ascorbic acid(VC).The variation of viscoelasticity of simulated cream was studied by spray drying of 5%hydrolysate SPH and modified starch.The formula was optimized by response surface.The optimal conditions of main ingredients were as follows:SPH:Gluconic acid-delta-lactone:modified starch:moisture=25:0.5:19.5:55.