Effect of Calcium Ions in Sorghum Beer Mashing

One of the problems in sorghum beer brewing is that of sugar production. This is because sorghum malts are low in diastatic activity, the grist contains a high proportion of adjunct and in some brewing processes conversion is carried out at pH 4. Since the positive effects of calcium ions on alpha-amylase activity are well described, the use of additional calcium in sorghum mashing was investigated. Mashing at pH 4.5 in the presence of 0.1% calcium acetate (227 ppm Ca) resulted in almost complete conservation of diastatic activity during conversion and higher reducing sugar production compared with tap water (31 ppm Ca). At a mash pH of 4, a calcium ion concentration of approximately 200 ppm gave maximum reducing sugar production and wort yield and increased extract. Under these conditions, some alpha-amylase activity was detected at the end of the conversion, whereas without calcium no alpha-amylase activity was detected. It, therefore, appears that improved conversion took place due to the conservation of alpha-amylase activity by calcium ions. The inclusion of additional calcium ions in sorghum beer mashes also enabled the same amount of sugar production compared with straight tap water but using a substantially lower proportion of malt in the grist.