EFFECT OF MASHING AND FERMENTATION TIMES ON THE QUALITY OF SORGHUM (Sorghum Bicolor) BEER

Abstract

Among cereal grains sorghum is the second candidate next to barley for use of in modern brewing particularly in the context of Africa arid agriculture. Unlike other African countries, sorghum malt utilization in Ethiopian modern brewery industry is virtually non-existent. This study was conducted to evaluate the effect of mashing and fermentation times on wort and beer quality parameters of selected sorghum variety(Teshale). The treatments consisted of factorial combinations of three levels of mashing time (1:55, 2:05 and 2:15 hrs) and three levels of fermentation times (120, 132 and 144 hrs).The experiment was laid out in a 3x3 factorial of complete random design (CRD) with three replications. Sorghum wort were prepared under controlled malt condition (6 h steeping in 0.2% NaOH solution tap water followed by 18 hr more steeping with 1 hr aeration at 3 hrs interval. At the end of steeping germination was carried out for 96 hr at 28 oC about 95% RH. Malt was dried at 50oC for 24 h and mashing at 70oC) in the laboratory. Sorghum beer also prepared under controlled condition (90 mins boiling of wort with hop at 85oC, cooling and 8-10oC fermenting) in beer factory laboratory. The data were analyzed by the software SAS 9.1. Results of the study showed that, mashing and fermentation times had a significant effect on sorghum beer quality. The FHWE(%), color, pH, bitterness (BU unit),wort viscosity(cp), filtration time(min) and free amino nitrogen(FAN) of sorghum wort were in range of 76.5-81.53%, 3.39-3.50 oEBC, 5.85-6.35, 20.62-26.57 BU, 1.5-1.61 cp, 43.63-60.53 min, 216.9-225 mg/L respectively. The sorghum beer original extract, pH, apparent degree of fermentation (ADF), color, bitterness (BU unit), alcohol content(v/v%), haze value, and CO2 concentration(gm/L) were found to the range from 10.93-12.52oP, 4.23-5.30, 73.36-81.33%, 4.93-5.35 oEBC, 14.80-15.63 BU, 4.33-5.36 v/v%, 0.99-1.85, and 3.60-5.95 mg/L. respectively. Significant difference (P<0.05) in rating for flavor, aroma, taste and overall acceptability was observed between the products as evaluated by sensory panelists. The iodine test of sorghum grain completely negative and higher wort extract at both 2:05 h and 2:15 h of mashing times. Generally, sensory analysis revealed that the most acceptable products were those of mashing time of 2:05 at 132 h of fermentation time, mashing time of 2:05 h at 144 h of fermentation time, mashing time of 2:15 h at 132 h of fermentation time and mashing time of 2:15h at 144 h fermentation time. This study showed that the optimum mashing duration of the sorghum malt could be around 2:05 h and 2:15 h. Among the fermentation times 132 h and 144 h produced better beer quality than 120 h, possibly on account of higher Original extract, alcohol content, ADF and good in other parameters.