Enzymatic Modification Of Pea Protein Isolate And Its Application

Pea protein is a high-quality,perfect plant protein resource,and it is gradually becoming a popular alternative to traditional proteins such as animal protein,whey protein and soy-derived protein.However,the commercial pea protein produced by the current domestic processing technology is susceptible to heat denaturation,low solubility,poor functionality,poor flavor and taste,which greatly limits its application in foods.Therefore,how to improve the overall properties of pea protein to make it more widely used in foods is an urgent problem to be solved.This subject aims to improve the overall properties of pea protein through enzymatic modification.The specific research results are as follows:(1)Glutaminase was used for enzymatic hydrolysis of pea protein isolate(PPI),and the effects of different degrees of deamidation on the structure,physicochemical and sensory properties of PPI were analyzed.The results showed that the glutaminase treatment significantly increased the suspendability,?-potential and surface hydrophobicity(H₀)of the PPI samples(p<0.05),and reduced the average particle size(d_3,2 and d_4,3)of the PPI samples,but did not change the primary structure and subunit composition of PPI.The results of infrared spectroscopy showed that the proportion of?-sheets,antiparallel?-sheets and aggregates of glutaminase-modified samples(GPPI)significantly decreased,while the proportion of?-turns and?-helices significantly increased.GC-MS analysis showed that the content of aldehydes and ketones(main components that cause beany flavor)in the GPPI samples was significantly lower than that in untreated PPI-0h sample,while the content of esters significantly increased.The results of sensory evaluation showed that glutaminase treatment can significantly improve the homogeneity,dispersibility and suspendability of PPI,while reducing the beany flavor,bitterness,feelings of grittiness and lumpiness.(2)Phytase was used for enzymatic hydrolysis of PPI,and the effects of phytase treatment on the structure,physicochemical,nutritional and sensory properties of PPI were analyzed.The results of single factor and orthogonal experiments showed that the optimal enzymatic hydrolysis conditions were as follows:50°C,p H 5.5 and enzyme dosage 0.04%.Further studies showed that phytase treatment significantly reduced the suspendability,average particle size and surface hydrophobicity(H₀)of PPI samples,but did not change the primary structure and subunit composition of PPI.The results of infrared spectroscopy showed that the proportion of aggregates of phytase-modified samples(PPPI)significantly increased from 17.92%to 29.05%,while the proportion of?-sheets,?-turns and antiparallel?-sheets significantly decreased.Nutritional analysis showed that the simulated gastric digestibility and simulated gastrointestinal digestibility of PPI samples increased significantly over time,and the final digestibility of PPPI-1h samples was as high as 79.63%.At the same time,phytase treatment improved the bioavailability of PPI's minerals(Ca,Zn,Fe).The results of sensory evaluation showed that the phytase treatment reduced the homogeneity,dispersibility and suspendability of PPI,but still weakened the feelings of grittiness and lumpiness.(3)The effects of two enzyme modifications on the functional properties and metal chelating ability of PPI were studied.The results showed that glutaminase treatment improved the solubility of PPI,especially the solubility under alkaline conditions.Phytase treatment shifted the isoelectric point of PPI from p H 4.5 to 5.0,but did not significantly improved the overall solubility.Regarding water binding capacity,glutaminase treatment did not significantly change the water binding capacity of PPI,while phytase treatment significantly improved it.Regarding oil holding capacity,both enzyme treatments significantly improved the oil holding capacity of PPI,and the oil holding capacity of GPPI samples was stronger.Regarding foaming ability and foam stability,the foaming ability of GPPI samples was much higher than that of PPI-0h and PPPI samples,but the foam stability was not as good as that of PPI-0h and PPPI samples.The difference in foaming ability and foam stability between PPI-0h and PPPI samples was very small.Regarding emulsifying ability and stability,compared with PPI-0h,emulsifying ability of GPPI samples was decreased and the emulsifying stability was improved,while the emulsifying ability of PPPI samples was slightly improved,and the emulsifying stability had little change.Regarding the gel properties,the gel strength of the thermo-induced gel of all PPI samples was not high.Among them,the gel strength of the GPPI samples was significantly lower than that of PPI-0h,and the gel strength of the PPPI samples was significantly increased.In terms of metal chelating ability,glutaminase treatment significantly enhanced the chelating ability of calcium,zinc and ferrous ions in PPI samples,and the chelating ability of ferrous ions was the best,increasing from85.34%to 91.27%.Phytase treatment had little effect on the chelating ability of zinc ions in PPI samples,while the chelating ability of calcium and ferrous ions decreased.(4)Evaluate the application effects of GPPI and PPPI samples in chocolates and plant protein drinks.PPI-0h,GPPI-12h and PPPI-1h were applied to chocolates at the proportions of 5%,10%and 15%,respectively.It was found that the range of color values of all chocolate samples had little change,and all of them were brown.The hardness of chocolates prepared by PPPI-1h samples was the highest,while that prepared by GPPI-12h samples was the lowest,and the melting peak value and melting enthalpy of all PPI-added chocolates were lower.The results of sensory evaluation showed that the chocolate samples of 1-5%,2-5%,2-10%and 3-5%had a smoother appearance,a glossy surface,a rich and mellow aroma,and a more delicate and smooth taste.PPI-0h,GPPI-12h and PPPI-1h were also applied to prepare dairy and non-dairy PPI drinks.It was found that compared with non-dairy drinks,dairy PPI drinks had higher viscosity,greater turbidity,better stability and higher centrifugal precipitation rate.The results of sensory evaluation showed that three PPI drinks samples of B1,B2 and B3 were more pure and uniform in color,richer in aroma,and more delicate and mellow in taste.