Preparation Of Umami Peptides In Soybean Meal And Exploration Of Taste Mechanism

Soybean meal is the main by-product obtained after soybean oil extraction.It is rich in protein,amino acid and other nutrients and has extremely high development potential.Among them,soybean is desolventized at high temperature to obtain high-temperature soybean meal.At this time,the protein has undergone a high degree of denaturation and its solubility is reduced.It is widely used in the feed industry and is seldom used in the food field.In this study,high-temperature soybean meal was used as raw material to prepare umami peptides by enzymatic hydrolysis of soybean meal with endonuclease and exonuclease,and the mechanism of flavor formation was explored.In this study,high temperature soybean meal was hydrolyzed by endoenzyme including papain,neutrase,alcalase,bromelain and trypsin.Firstly,the molecular weight distribution of the endonuclease hydrolysate was analyzed by SDS-PAGE,and the endonuclease was preliminarily screened,of which trypsin had the worst enzymolysis effect compared with other proteases.Their hydrolysis effects were further compared,with degree of hydrolysis（DH）and taste dilution analysis（TD）as indexes.It was determined that the optimal protease is neutrase.The effects of 3 factors including enzyme concentration,pH and hydrolyzing time on DH and TD was studied.Based on the single factor test,the L₉（3⁴）orthogonal test was used to optimize the enzymatic hydrolysis process.The DH in neutrase hydrolysate reached 31.16%,with the following conditions:enzyme concentration 7500 U/g,pH5.8,hydrolyzing time 5 h.Which laid a theoretical foundation for the high-quality utilization of high-temperature soybean meal.The exoenzymes selected to hydrolyze high-temperature soybean meal includes protamex and Flavourzyme.The molecular weight distribution of exonuclease hydrolysate was analyzed by electrophoresis.It was found that both of them had better enzymatic hydrolysis effect.Then,the DH and TD were used as screening indexes to compare the enzymatic hydrolysis effects of Flavuzyme and protamex.It determined that the optimal protease is Flavourzyme.The single factor experiment was used to investigate the optimum addition amount of the enzyme,pH and enzymolysis time.The L₉（34）orthogonal test was utilized to optimize the enzymatic hydrolysis process.The DH in Flavourzyme hydrolysate reached 27.80%,with the following conditions which were enzyme concentration 22 U/g,pH 5.8,hydrolyzing time 2.5 h.On this basis,the endo-and exo-enzymes with good enzymolysis effect were selected,and the combination scheme of seven proteases was designed to carry out enzymolysis on high-temperature soybean meal by means of continuous enzymolysis of them.The study found that the soybean meal protein utilization rate of the seven schemes was more than 80%,which realized the efficient utilization of soybean meal protein.Sensory analysis showed that the taste characteristics of the seven enzymatic hydrolysis products were significantly different.Neu-p group is very similar to monosodium glutamate and disodium nucleotide（I+G）.The exploration of the taste mechanism showed that the taste characteristics of the enzymatic hydrolysis products were significantly related to the degree of hydrolysis of soybean meal protein and the proportion of umami amino acids in peptides.Comprehensively considered,the enzymatic hydrolysis products prepared by the Neu-p group,that is,the continuous proteolysis of neutrase,papain and Flavourzyme,are expected to develop into umami peptides.The development of this research laid a theoretical foundation for the enzymatic hydrolysis of high-temperature soybean meal to produce seasoning base materials,and at the same time provided some reference for the selection of raw materials in the production and application of other protein-related foods.