Preparation Of Yeast Extract From Spent Brewer’s Yeast And Of Pork Flavor Agent Development

Yeast extracts(YE)are widely used in the food industry and feed industry.The spent brewer’s yeast as a by-product of beer production is a more suitable raw material for the production of yeast extracts,which can reduce the product cost and can also make the spent brewer’s yeast be reasonably used.In this study,a protease-assisted autolysis method was used to prepare yeast extract from spent brewer’s yeast,and the volatile flavor components in the yeast extract were analyzed and identified.Using this yeast extract as the main base material,a pork flavor agent was trial-produced.The all experiment came to the following conclusions:1.The results have confirmed that papain,neutral protease and trypsin have varying degrees of enzyme promoted autolysis effects on spent brewer’s yeast,and could be used as autolysis-promoters.2.The test results of the amount of enzymes added shown that:the most suitable amount of papain was 0.4×10-1g/mL,led to both the free amino acid nitrogen yield and the solids yield reach the maximum.The neutral protease and trypsin were 0.6×10-2g/mL and 0.025×10-2 g/mL,respectively.The test results of the optimal pH value of the enzyme promoted autolysis system shown that:the result shown:the optimal pH value of papain was 5.5,at which time both the free amino acid nitrogen yield and the solids yield reach the maximum.The neutral protease and trypsin were 6.0 and 5.0 respectively.The test results of perspective of enzymolysis reaction time shown that:the result shown:the most suitable enzyme promoted autolysis reaction time for papain and neutral protease was 36h,while trypsin was 30h.3.Comparing the effects of the agents for enzyme promoted autolysis,papain,neutral,trypsin,alcohol and salt,it was found that neutral protease is the most suitable agengt for enzyme promoted autolysis processing.The optimized enzyme promoted autolysis process conditions were:the amount of neutral protease was 0.6×10-2 g/mL,the pH value of the system was 6.0,the system temperature was 50℃,the reaction time was 36h.The results shown that the solid yield of the yeast extract obtained reached 66.06%,and the yield of free amino acid nitrogen reached 5.63%.The prepared yeast extract then was concentrated,and the appearance of the final product was creamy yellow-brown with a fresh and fragrant flavor.4.The final yeast extract was analyzed by GC-MS,and a total of 18 substances were identified,including acids,esters,alcohols,ethers,aldehydes and other compounds.Among them,acid and ester compounds both accounted for 27.8%,alcohols and aldehydes both accounted for 11.1%,ketones and ethers both accounted for 5.6%,and other compounds accounted for 11%.5.In this study,yeast extract was used as raw material to try to prepare pork flavor agent.The Maillard reaction temperature,time duration and pork fat adding proportion were selected as variable factors,and the sensory evaluation score of pork flavor agent was used as the evaluation index.The results shown that the factors affected the sensory of pork flavor agent were:pork fat addition,reaction temperature,reaction time,respectively.The typical formula for preparing pork flavor agent was:every 100g yeast extract by adding 1g salt,4.32g lard,0.5g xylose,1.5g cysteine,1g arginine,1.5g glycine.The suitable Maillard reaction temperature was 111.19℃,reaction time duration was 1.52h,that process could produce a flavor agent with strong pork smell.After the actual application in the processing of braised pork products,it was found that the effect of this pork flavor agent was also quite satisfactory.