Quantification of ethanol and identification of other chemical constituents in homemade morula beer using gas chromatography-mass spectrometry (GC-MS)

Morula (Sclerocarya birrea) beer is a seasonal homemade alcoholic beverage made from morula fruits pulp. Unlike the commercial morula alcoholic beverage, the alcohol content of homemade morula beer is not known. The major challenges with homemade alcoholic beverages arise from batch-to-batch differences in product quality and safety due to the variability of raw materials and lack of quality control. Consequently, the alcohol content of alcoholic beverages made by the same individual may differ. In this study, a validated liquid-liquid extraction gas chromatography-mass spectrometry (GC-MS) method is used for the quantification of ethanol and identification of volatiles in homemade morula alcoholic beverage. The analysed samples contained ethanol with concentrations ranging from 0.5 to 5.8% v/v depending on the number of days the sample was fermented. Other volatile compounds that were identified were acetic acid, propanol, propanal, butanal, 3-methyl-1-butanol; 2-methyl-1-butanol, butanoic acid, iso-amyl acetate, butanoic acid ethyl ester, benzyl alcohol, phenyl ethyl alcohol, lactic acid, humulene, decanoic acid ethyl ester and 2-methyl-1-hexadecanoic acid ethyl ester. The volatile compounds were found to decrease over time. These results provide a validated method for the characterisation of homemade alcoholic beverages and information on the quality of morula beer.