Control And Regulation Of Diacetyl In Beer Fermentation

This research embarked from the beer yeast project fungus,adopted the diacetyl resistance processing method,through the beer yeast in 1.5 mg/L,2.0 mg/L,in 2.5 mg/L diacetyl content gradient culture medium raised,screening can carry on under the highly concentrated diacetyl content existence the normal metabolism activity the anti-diacetyl variation yeast strain,carried on the diacetyl 5 generation of intermittence patience raise, again carried on the low temperature fermentation experiment,took diacetyl peak value content low 1 to carry on the continual patient raise,after raised the column class to add the fermentation fluid to tame 7d continuously,separates from the column screens 5 fungi to carry on the low temperature fermentation experiment,obtains the diacetyl peak value content to be lowest,the cell size medium degree of fermentation high strain YZB.Through the research optimal strain YZB in the different wort nutritional conditions and under the fermentation raised condition fermentation situation,summarized the beer fermentation flavor by-product formation and the accumulation rule,the analysis inorganic ion pair by-product influence,obtained the best fermentation nutritional conditions and the raise technological conditions.Regarding the wort ingredient influence,to the wort density, alpha - the amino nitrogen content,in wort the chemical additive iron,the zinc and the selenium ion content conducts the research,studies it to the yeast multiplication as well as the diacetyl production and the return to original state influence,and obtained these ion ingredient the appropriate recruitment.The fermentation process condition influence,mainly on the host yeast temperature,the saccharomycetes vaccination quantity uses in the diacetyl the return to original state,reduced the beer the mature time to conduct the experimental study.The experimental conclusion is as follows:1.Selective breeding produces diacetyl beer yeast strain YZB lowly after the EBC enlargement experiment,its diacetyl peak value was 0.38mg/L,the ratio embarked the strain to drop 40%⁴2%.After the fermentation had finished in the liquor fluid the diacetyl content is 0.08～0.09 mg/L,the true degree of fermentation is 65.4%～65.9%,other fermentation performance basic maintenance was invariable,after continuously switches over 7 generation of its hereditary features to be stable. 2.Low diacetyl strain YZB best wort nutritional conditions findings indicated that,the original wort density 11.0%and alpha - amino nitrogen content 165 mg/L,added 0.70 mg/L in wort FeSO₄·7H₂O,or added 0.75 mg/L ZnSO₄·7H₂O,added 200 mg/L in the malt preparation Na₂SeO₃,was advantageous in the control low diacetyl content,the beer flavor basic invariable,the fermentation time may reduce one half.3.Low diacetyl strain YZB best fermentation condition findings indicated that,When the host fermentation temperature 13℃,the vaccination quantity was 12%,the strain fermentation speed speeded up,was advantageous in obtains the style palely crisp and stable good beer.It could control the low diacetyl content,reduced the fermentation time, saved the production cost,enhanced the economic efficiency.