Study On Preparation And Application Characteristics Of Soybean Meal Umami Peptide

Soybean meal is a by-product of soybean oil extraction.At present,there are some problems such as single utilization mode,low efficiency and lack of deep processing.In addition,the bitter taste and anti-nutritional factors of soybean protein limit its application in food field.This paper uses soybean meal as raw material,the koji was inoculated with Aspergillus oryzae and Aspergillus niger and hydrolyzed,the production cost of hydrolyzing using the compound protease system produced by kospi is low,and the use of Aspergillus niger acid protease to soy peptide debitterizing.Then,the soybean meal umami peptide was separated and purified by ethanol fractional separation and dextran gel chromatography to expand the utilization of soybean meal.Using soybean meal as raw material,the soybean meal koji was prepared with Aspergillus oryzae and Aspergillus Niger（3:1）and hydrolyzes.Hydrolysis degree as an index,exploring the best single factor of hydrolysis and throughing response surface optimization to obtain the best hydrolysis conditions:hydrolysis p H value of natural state（default p H is 5.5）,solid-liquid ratio of 1:2.1（g/g）,temperature of 44.50℃,hydrolysis of 5.1 d,the degree of hydrolysis obtained through verification experiment is 21.50%（g/g）.The soybean meal umami peptide was isolated and purified by ethanol separation and dexan gel chromatography.After filtration,enzyme removal and centrifugation,ethanol is continuously added to the hydrolysate.When the volume fraction was 35%,60%and 85%,componentⅠ,componentⅡ,componentⅢand componentⅣwere successively obtained.The sensory score of componentⅢwas the highest and its yield was 5.10%,and the content of umami amino acid was the highest with 8.69 g/100g,among which glutamate accounted for67.54%.The molecular weight of 1000～3000 Da accounted for the highest 51.74%;Sphadex G-15 glucan gel was used to separate and purify componentⅢand obtain four components.ComponentⅢ-2 had the highest sensory score of umami and as the target product of soybean meal umami peptide.Its yield was 3.25%,containing about 63%soybean peptide,20%total sugar and the highest umami amino acid content was 9.55 g/100g,among which glutamate accounted for 91.54%.After ethanol fractional separation and dextran gel chromatography,umami amino acid content in the freshest fractions increased from 8.69 g/100g to 9.55 g/100g,bitter amino acid content decreased from 10.06 g/100g to 6.69 g/100g,umami score significantly increased,bitter score significantly decreased.The results showed that 60%～85%ethanol and dextran gel chromatography could be used to extract umami peptides quickly and in large quantities,and the bitterness of umami peptides could be effectively reduced.The umami,physical and functional properties of the soybean meal umami peptide were studied.The results showed that the umami threshold was 350 mg/L.Soybean meal umami peptide had higher dispersive stability and solubility in acidic environment（p H 3～7）,and the emulsification increased with the increase of mass fraction.The DPPH free radical scavenging rate of soybean umami peptide was about 71.32%of vitamin C at the same concentration,and the reducing power of soybean umami peptide to Fe³⁺was about 52.93%of vitamin C,indicating that it had antioxidant function.The cholesterol-lowering effect of soybean umami peptide was about 59.07%of corolenamide at the same concentration,indicating that it had cholesterol-lowering function.Soybean meal umami peptide was compared with two kinds of commercially available umami peptides（soybean extract and soybean peptide cream）with a uniform solid content of65 g/100m L,and the best addition amount of soybean meal umami peptide in the soy sauce.The results showed,Amino acid nitrogen content:soybean extract>soybean meal umami peptide>soybean peptide cream;Reducing sugar content:soybean meal umami peptide>soybean extract>soybean peptide cream;Precipitation rate:soybean peptide cream>soybean extract>soybean meal umami peptide;Sensory evaluation:Compared with the others,soybean meal umami peptide had no bitterness,and its umami taste was similar to that of soybean extract,with light fragrance,but the sauce taste was slightly weaker.Combined with sensory evaluation and precipitation rate of soybean meal umami peptide in the soy sauce,the optimal addition amount of soybean meal umami peptide was determined to be 0.6%,which provided data reference for the application of soybean meal umami peptide in the soy sauce.