Optimization of malting conditions for two landraces of West African sorghum and influence of mash bio-acidification on saccharification improvement

Abstract

Traditional sorghum beer processing based on uncontrolled malting and mashing conditions limits significant saccharification. We optimized the amylase activity of west African sorghum to improve saccharification. Furthermore, we bio-acidified the mash with Lactobacillus plantarum (ND-32, ND-130), Lactobacillus paracasei ND-34, and studied its impact on wort nitrogen, especially the branched amino acid content. The β-amylase content of the red sorghum malt used for traditional beer processing was 261 U/g of dried malt when sorghum seeds were steeped to 42% and germinated at 27 °C for 5 days. Despite the optimization of hydrolases, protein hydrolysis was still limited. Sorghum mash pre-heating and bio-acidification increased the wort free amino nitrogen content up to 27%. The contents of several amino acids, including the branched amino acids valine, leucine, and isoleucine, were highly improved. Our new approach based on mash pre-heating and biological acidification helped to increase the wort branched amino acid content by up to 50%. The branched amino acids valine, isoleucine, and leucine are respective precursors for isobutanol, amyl alcohol, and isoamyl alcohol, all of which are critical components of beer aroma.