Sprouted sweet potato flour as a saccharification enhancer to improve the brewing properties of pearl millet malt

Abstract

The use of high enzyme sprouted sweet potato flour (SSPF) as a saccharification enhancer to improve the brewing properties of pearl millet (Pennisetum glaucum, L.) was investigated. The results show a linear relationship between hot water extract (HWE) and increased substitution levels of SSPF up to a maximum of 363oL/kg at 40% substitution (40SM). Similarly, diastatic power (DP) increased from 21oL in 100% millet malt to 24 and 33oL at 20% (20SM) and 40% substitution (40SM). This can be attributed to the high amylolytic potential of sprouted sweet potato flour. Saccharification time reduced from 40 to 10 minutes for 20SM and 40SM (SSPF/millet malt) mash samples compared to the barley malt control. With increasing levels of SSPF substitution, the free α-amino nitrogen of SSPF/millet malt wort samples declined from 154 mg/L in all millet malt sample to 126 mg/L in 40SM sample. However, all samples had a high rate of apparent attenuation in fermentation. This substitution method offers opportunities to optimise the brewing potential of millet in countries where the cost of importation of barley malt is prohibitive. However, the levels of modification in the composite samples, suggest sweet potato flour could be used in the brewing and distilling industries alone or together with malted millet.