Optimization And Research On Preparation Technology Of Vegetable Meat Flavor Based On Yeast Protein

Yeast is widely used in food,brewing and industrial production,but the by-product of production-yeast cells often cause huge pollution and waste due to improper treatment.In recent years,with the deepening research of Maillard reaction flavor,the flavors produced by different protein sources have become more extensive.But at present,the research of Maillard reaction flavor which is applied to yeast protein source is still in blank.In this paper,the preparation of Maillard reaction hydrolysate from microorganism fermentation and enzymatic hydrolysis was carried out from yeast protein,and then added food additives such as reducing sugar,amino acids and vitamins to prepare meat flavor.The main results are as follows:1.Physical and chemical properties of food yeast powder:the appearance is yellowish brown powder,with special smell and no peculiar smell.The crude protein content is 59.10±0.03%,the moisture content is 3±0.19%,and the crude ash content is 6.36±0.48%,The total nitrogen content is 9.76±0.18%,and the amino nitrogen content is 0.1±0.06%.2.Screening of fermentation strains:in this study,five strains of bacteria with strong protein degradation ability preserved in the laboratory were used as the test strains.The preliminary screening was carried out through the transparent circle experiment,and the secondary screening of yeast protein degradation fermentation experiment was carried out with the degree of hydrolysis as the index.A test strain with strong protein degradation effect and gram positive staining,Bacillus megaterium,was obtained as the fermentation strain of this experiment.3.Optimization of fermentation process:The effects of single factor and orthogonal experiments（fermentation time,different substrate content,C-source type,different fructose syrup concentration,inorganic salt type,Bacillus monocytogenes inoculation,fermentation temperature）on yeast protein degradation and fermentation process were investigated.The effect of single factor on response value during yeast protein degradation fermentation was determined.The optimum fermentation conditions were:12h fermentation time,4g/100m L feed water ratio,1g/100m L fructose syrup,0.2g/100m L calcium chloride,5%inoculation（v/v）and37℃fermentation temperature.The hydrolysis degree of fermentation solution obtained under these conditions reached 53%and the flavor was good.4.Optimization of enzymatic hydrolysis:The effects of various factors（enzyme type,enzyme addition,p H,enzymatic hydrolysis temperature）on yeast proteolysis were investigated by single-factor assays and response surface assays.The effect of single factors on response value during yeast proteolysis was determined and optimal conditions were obtained for enzymatic activity addition of2925U/100m L,p H=5.66,temperature 46.51℃,time 5h.The hydrolysis degree of hydrolysate obtained under these conditions was further improved by 30%compared to that obtained after fermentation.5.Analysis of physicochemical properties and aroma of hydrolysate:amino acid composition and molecular weight distribution of food yeast powder,fermentation broth and hydrolysate were analyzed,and the aroma composition of hydrolysate was analyzed.The results showed that after fermentation by Bacillus megaterium,on the premise of good flavor of fermentation broth,free amino acids changed greatly,in which the composition and content of human essential amino acids and aromatic amino acids were greatly improved after fermentation,After enzymatic hydrolysis,the content of free amino acids was 2 times higher than that of fermentation broth,but the proportion of hydrolyzed amino acids changed little.Among the free amino acids,human essential amino acids accounted for 67.29%of the total amino acids,and the amino acids contributing to meat flavor accounted for21.19%of the total amino acids.After fermentation,the molecular weight is mainly concentrated below 1000da.After enzymatic hydrolysis,the total molecular weight less than 1000da is further increased.6.Mellard Reaction System Establishment and Fragrance Analysis:Based on yeast protein hydrolysates,a Mellard model system of amino acid-reductive sugar was studied to determine the optimal conditions for Mellard reaction:regulation of hydrolysate p H=6,addition of 5%（w/v）reductive sugar（glucose:xylose=2:3）,0.5%（w/v）L-cysteine（w/v）,0.2%（w/v）vitamin B₁,0.2%（w/v）salt,0.2%（w/v）arginine,mix well and react at 120℃for 50min.Under these conditions,the Mellard reaction product with certain meat flavor can be prepared.The results showed that the aroma of Maillard reaction products were mainly meat aroma,barbecue aroma and fried melon seeds aroma.7.Determination of oil oxidation conditions and aroma analysis:7 plant oils were added to the established Maillard reaction system to add flavor,taste and quality analysis.The results showed that 0.3%（v/v）rapeseed oil added reaction could provide more essential meat flavor for essential flavor.