The Use And Management Of Beer Yeast

Beer yeast in the process of use and management,the biggest challenge is to ensure the consistency of the process performance of beer yeast(flocculation,fermentation rate,etc.)to the product technical parameters(flavor,physical and chemical analysis,etc.).The best way to store?propagates beer yeast step by step and recovery can minimize the harm.Therefore,in order to further enhance and improve beer flavor stability.We must first ensure that beer yeast of good performance and best form in the process of the use and management.This article first through performance assessment of yeast strain G to determine whether the performance changed.Test indexes including hypoglycemic speed(CO2 weightlessness rate),fermentation degree,alpha amino nitrogen assimilation rate,diacetyl reduction,flavor substances and acetic acid,etc.Through the performance test,the G strains fermentation performance mainly embodied in the fermentation degree and alpha amino nitrogen assimilation rate is low,fermentation ability is insufficient,ester material content is slightly lower,and the content of acetaldehyde and acetic acid are high.In order to improve the performance,the key control points such as medium concentration,oxygen filling method,switching time in laboratory culture phase was optimized.Before optimization,the medium concentration of alpha amino was between 130-160 mg/L,it does not meet the demand for nitrogen source of yeast culture premise.After the optimization,wort concentration were uniform for 12 °P in the process of laboratory,and the wort were diluted from 13 °P saccharifying wort,which diluted by alpha amino nitrogen content increased to about 200 mg/L,guarantee the yeast has adequate nitrogen source.After contrast found yeast number increased by about 10-20 x 10~6 cells/mL.Before optimization,manual filling oxygen exists heterogeneity,and the night unable to oxygenate.Optimized for the rock bed 250 r/min,5 min/3 h,a total of 8 times throughout the day.The oxygen-filling method of the cask can be changed from pure oxygen to compressed air,every 2 h oxygen 20 min.In the jar,yeast cell concentration can reach 40-80 x 10~6 cells/mL.In the same medium,under the same quantity of optimizing oxygen filling way after making yeast increased nearly 20-30 x 10~6 cells/mL,and not easy to appear the phenomenon of aging,more in line with the law of supply of aerobic bacteria growth.In order to avoid the yeast was aging,maintain growth advantage,shorten the culture time.According to the rule of budding rate of 30%and about 2 h before the end of logarithmic phase is the best results,We optimize the transit time.In test tube stage,the optimal switching time of 23.5 h;Triangle flask stage optimal switching time of 17 h;Pap bottle phase optimal switching time is about 19 h.The optimized transfer yeast are in the best state.After optimization,the effect of the expansion process on the species performance was eliminated.G strains has been used for more than 10 years,its flavor characteristics and taste has been recognized by consumers.And in the process of long-term use,we found the consistency of fermentation index was declined.Through performance test also proved that the strain of the performance degradation.Therefore,this paper tries to based on strain fermentation data rejuvenation screening G strains,from '03,' 05,and 09 three original strain at the beginning of 90 strains of sieve get 15 strains.Choose T,X and 75#strain(the worst performing 75#)to screen.The final test 37#strains screened out for production.From the experimental data,the mass production stage yeast expansion,while under the influence of pouring tank but the overall index is more ideal.In order to ensure the quality of beer,purification and rejuvenation should be carried out regularly.Hope can make strain has the stable fermentation speed and recycled,consistent diacetyl reduction time and evaluation results.