Differences Research On Top And Bottom Fermented Wheat Beer

Comparion of top fermented and bottom fermented wheat beer during the fermentation process was carried out on100liters of beer experiment in our laboratory. The results showed that the diacetyl and total acid content of top fermented wheat beer were higher than bottom fermented wheat beer during fermentation; the amino nitrogen content and pH value in top fermented wheat beer were lower than bottom fermented wheat beer; the alcohol and sugar degree was differential less, and all of those were in the natural range.High Performance Liquid Chromatography (HPLC) was employed to analyze the change of fermentable sugar components in wheat wort during two different fermentation process, and a detailed follow-up study was carried out on top yeast (No.354) and bottom yeast (Germany DAB) in the use of sugars by adding additional sucrose. Results showed that the content of five kind of fermentable sugar were0.23,1.14,0.19,5.52and1.08(g/100mL) respectively. Two kinds of yeasts are capable of sugar utilization in the sequence of sucrose, and then glucose, fructose, maltose and maltotriose; concentrations of glucose and fructose in wort increased in the initial stage of fermentation, and they had the same added amount; No.354yeast had the ability of fermenting maltose at a high concentration of glucose, the effect of glucose repression is not obvious as in Germany DAB yeast.The G-75glucosan gel filtration chromatographic was developed to separate soluble protein constituents in wheat wort, top fermented wheat and bottom fermented wheat beer, and the content and molecular weight distribution of various protein components were detected by Folin-phenol method and SDS-PAGE technology. Results showed that the components of protein and peptides from the wort and beer were very similar with three main components; the total soluble protein content of wort, top fermented wheat beer and bottom fermented wheat beer were5045.9mg/L,4251.9mg/L and4271,4mg/L, respectively; the corresponding protein molecular weight turned out to between14-25kDa and37.6-48.0kDa.The volatile aroma components in the beer getting from the two processing were analyzed by auto static sampler combination capillary column GC. The result showed that eight compounds, i.e. acetaldehyde, N-propanol, ethyl acetate, isobutyl alcohol, isoamyl alcohol, isoamyl acetate, ethyl hexanoate and ethyl octanoate were separated thoroughly. The content of esters and higher alcohols in top fermented wheat beer were22.84mg/L and155.12mg/L, and which in bottom fermented wheat beer were6.43mg/L and66.20mg/L, respectively. The aroma of top fermented wheat beer was gentler, although esters and higher alcohols in the two kinds of beer were within the scope of the normal content of light beer.