Effect Of Glycation Of Soybean Protein On The Formation Process And Physicochemical Properties Of Whole Soybean Curd

Whole soybean curd is a new bean product which is made from whole soybean as raw material.However,there are more soybean soluble sugars involved in the formation of whole soybean curd compared with the traditional filtered curd.These ingredients have great influence on the properties of soybean protein gel.This study mainly explores the effects of soluble soybean polysaccharides(SSPS)and soybean oligosaccharides(SBOS)on the formation process of gel and the influence of its physical and chemical properties of soybean protein isolate(SPI)gel,glycinin(11S)gel and β-conglycinin(7S)gel induced by glucono-δ-lactone(GDL)and Transglutaminase(TG)complex coagulants respectively.Based on this,the differences in physicochemical quality of raw milk tofu,cooked milk tofu and whole soybean tofu prepared by dry ultrafine grinding are compared and analyzed.The main conclusions are as follows:1.The effects of SSPS concentration(0,2.5%,5%,10%,15% and 20%,w/w)on the formation process and physicochemical properties of SPI gel,11 S gel and 7S gel were investigated.Compared with SPI gel and 7S gel,11 S gel had the highest glycosylation degree,24.07%,when the SSPS addition was 20%,At the same time,the addition of SSPS had the greatest impact on the hardness of 11 S gel.With the addition of SSPS,the hardness of 11 S gel decreased from 546.18 g to 153.05 g,The results of infrared analysis,protein solubility,surface hydrophobicity and free sulfhydryl group showed that,with the addition of SSPS,the high-order structure of 11 S gel gradually changed,disulfide bonds were broken,electrostatic interaction decreased,non covalent interactions(hydrogen bonding and hydrophobic interactions)became the main driving forces.For 7S gel,the low amount of SSPS(2.5%,5% and 10%)made the protein structure more ordered,and had no significant changes in gel hardness and WHC.However,when the amount of SSPS added reached 15% and 20%,the random coil gradually increased,electrostatic interaction slightly increased,non covalent interactions(hydrogen bonding and hydrophobic interactions)decreased,resulting in a decrease in gel hardness.2.The effects of SBOS concentration(0,2.5%,5%,10%,15% and 20%,w/w)on the formation process and physical and chemical quality of SPI gel,11 S gel and 7S gel were investigated.The three proteins can all undergo glycosylation reaction with SBOS.The infrared results showed that the secondary structure of the three proteins was more orderly with the addition of SBOS.The results of protein solubility,surface hydrophobicity and free sulfhydryl group showed that with the addition of SBOS,the hardness of 11 S gel slightly decreased,but the storage modulus G’ continued to increase,disulfide bonds were broken,and non covalent bond interactions such as electrostatic interactions,hydrogen bonds and hydrophobic interactions gradually increased;For 7S gel,with the addition of SBOS,the hardness of its gel first increased and then decreased,non covalent interactions(hydrogen bonding and hydrophobic interactions)continued to decrease,and the electrostatic interactions gradually increased.3.The raw soybean curd,cooked soybean curd and whole soybean curd were prepared by dry superfine grinding method,In the process of tofu preparation,raw soybean milk,cooked soybean milk,coagulant added,85℃ enzyme free gel molding and cooling for 30 min,4℃ cold storage and ripening for 24 h,samples were taken at five time nodes.The results showed: In practical complex tofu systems,glycosylation reactions occur during the preparation of three types of tofu.The degree of glycosylation of raw milk tofu,cooked milk tofu and whole soybean tofu was 17.31%,23.89% and 14.76%,respectively.Use raw milk tofu as a control.For cooked tofu,the results of protein solubility,surface hydrophobicity and free sulfhydryl groups indicate that the occurrence of glycosylation reactions can destroy the disulfide bonds,non covalent interactions(hydrogen bonding and hydrophobic interactions)between protein molecules,resulting in an increase in free sulfhydryl groups and surface hydrophobicity.The destruction of covalent bond and non covalent bond resulted in the lowest gel hardness of cooked tofu.For whole soybean curd,glycosylation will have the same effect on it,but the results of protein solubility,surface hydrophobicity and free sulfhydryl groups showed that the existence of soybean dregs hindered the development of protein structure,inhibited the occurrence of glycosylation.At the same time,bean dregs existed in an insoluble phase,which will also affect the formation of disulfide bonds in protein gel,leading to the increase of free sulfhydryl groups.In conclusion,During the preparation of protein gel,SSPS and SBOS can undergo glycosylation with the protein,and the addition of SSPS and SBOS will change the structural properties and gel properties of the three proteins.In the actual complex whole soybean tofu system,glycosylation reactions can also occur between protein and sugar,but the presence of insoluble fibers prevents the expansion of the protein structure,thereby inhibiting the occurrence of glycosylation reactions.The discovery of this result can provide production and theoretical support for the development of whole bean curd products.