The Study Of Extracting Soybean Umami Peptides By Mucor Protease

Umami peptides come from a wide range of sources.They are a class of small molecular peptides that have an umami taste and can synergize with other taste-imparting substances to give foods a rich and delicate taste,usually with a molecular weight below 1,000 Da.It is rich in flavor,easy to digest and absorb,and has both nutritional value and special physiological functions.Therefore,how to purify the umami peptide and further explore its structural composition is of great significance to the development of new flavorings and to promote the industrial upgrading of flavorings in ChinaIn this paper,Mucor protease was used to hydrolyze soybean umami peptides.Firstly,the relationship between different enzymatic hydrolysis conditions and the changes of basic substances such as proteins and sugars,as well as the optimal enzymatic hydrolysis process were explored.According to the results of single factor test,a response prediction model was constructed to obtain the optimal process conditions.The optimal process conditions are enzymolysis temperature 34.3?,enzymolysis time 92.5 h,material-liquid ratio 1:2.2(g/g),without pH value adjustment.Under the conditions,it was predicted that the degree of hydrolysis is 5.637%.The result of verification test showed that the degree of hydrolysis was 5.62%,which is close to the predicted value,indicating that the response surface test design is reasonable and reliableFour fractions(E1,E2,E3 and E4)were obtained from the enzymolysis solution by using 40%,60%and 80%ethanol.The proportion of umami amino acids in E2 hydrolysis and free amino acids was the highest.The umami taste of E3 was the best,the content of umami amino acids in peptides was the highest,and there was a high proportion of sweet amino acids in both hydrolyzed and free amino acids.The TAV value of E3 free amino acids was similar to that of fresh sweet chicken soup.The TAV value of histidine was the highest except for umami amino acids.E4 was the most bitter.Under the optimal process conditions,the enzymatic hydrolysis was sufficient.The content of peptide segments with molecular weight less than 1000 Da of the four components all exceeded 90%,and there was a large number of peptide segments with molecular weight between 180 and 500 Da.The content of peptide segments with molecular weight between 500 and 1000 Da in E3 fraction was the highest.Most of umami peptides could be precipitated in 60%?80%ethanol solutionsThe accumulation of Maillard products was the highest when E3 was heated at 120? for 30 minutes.When compounded with diluted soy sauce,E3 could increase the umami while also increase the bitterness.R3 was prepared by adding glucose to E3 and heating at 120? for 30 min which could reduce bitterness and increase umami to a certain extentThree fractions(g-1,g-2 and g-3)was obtained using sephadex G-15 chromatography to separate and purify E3.From the result of sensory evaluation,it could be seen that the g-1,g-2 and g-3 flavor base notes were similar to MSG and the umami taste of g-lwas the best According to the data of hydrolyzed and free amino acids,it could be seen that there was a large amount of umami,sweet,and hydrophilic amino acids present both in g-1 and g-2.Most of the umami amino acids of g-3 existed as free amino acids,and there was a large amount of bitter and hydrophobic amino acids in the peptides.Sephadex G-15 chromatography was a simple and effective method for enriching umami peptides after ethanol precipitation and separationThe UPLC-MS/MS technology was used to separate g-1 which had the best umami flavor and amino acid sequences were identified.6 umami peptides,with molecular weights of 452.2,488.2,490.2,544.3,556.3 and 570.3 Da were detected.The amino acid sequences are PEHA(Pro-Glu-His-Ala),EDLL(Glu-Asp-Leu-Leu),DMEP(Asp-Met-Glu-Pro),DRGVV(Asp-Arg-Gly-Val-Val),DYFL(Asp-Tyr-Phe-Leu)and GELPR(Gly-Glu-Leu-Pro-Arg).