Sorghum beer production using Saccharomyces sp. isolated from palm wine as the pitching yeast and Garcinia kola as the bittering agent

Abstract

Beer production in Nigeria is dependent on imported brewery yeasts and hops, which consequently increases the cost of beer production. The current study was conducted to determine the effect of using indigenous strains of Saccharomycessp. in place of brewer’s yeast, and Garcinia kola as the bittering agent on beer quality. Saccharomycesspecies strains were isolated from palm wine, andSaccharomycescerevisiae specie selected using nitrates and lysine assimilation test. IndigenousS. cerevisiaewas used for beer brewing at different pitching rates (1×107, 2×107, & 3×107) using brewer’s yeast as the control. The effect of various concentrations ofGarcinia kola(0.1 ml, 0.2 ml and 0.3 ml) on beer taste and quality was later determined; beer brewed with hops served as the control sample. The physicochemical analysis showed that the pH, specific gravity (SG) and free amino nitrogen (FAN) values of beer brewed with local S. cerevisiae strain were between 4.32 - 4.52, 0.962 - 1.008, and 81.80 - 263.64 g/L, respectively while the alcohol value was from 5.12 - 11.16 ABV. However, pitching with 1×107 cells gave the best product and was therefore used for further analysis. Beer samples from wort pitched with local yeasts and brewed withGarcinia kolagave good quality beer comparable to the standard product. pH values of the products were in the range of 3.18 - 4.41, SG (0.962 - 1.006), FAN (16.87 - 81.80g/l), bitterness (8.83 - 17.83 EBU) and alcohol (5.38 - 11.16 ABV).