Mashing with Malted Grain Sorghum

Abstract

Malted grain sorghum is used in southern Africa to brew traditional sorghum (opaque) beer. Sorghum malt has good α-amylase activity but low β-amylase. Its starch has a high gelatinization temperature of 65–68°C. Sorghum beer mashing is performed with a large quantity of cooked starchy adjunct. Some of this adjunct starch is not saccharified and contributes to the opaque character of the beer. The sorghum malt starch is not substantially hydrolyzed because the normal mashing temperature, 55–60° C., is below its gelatinization temperature. lnvestigation of a wide range of mashing conditions revealed that a large increase in extract occurred over the temperature range of 65–70° C because of gelatinization and saccharification of the sorghum malt starch. Fermentable sugar formation was, however, maximal at only 65°C. When mashing was performed with an all-sorghum malt grist, high extract but low fermentable sugars were obtained at a constant mashing temperature of 75° C. Best all-around results were achieved with a triple-decoction mashing process that facilitated gelatinization and saccharification of starch and fermentable sugar formation. The particular properties of sorghum malt apparently enable mashing at elevated temperatures to produce worts rich in nutritionally desirable complex carbohydrates (dextrins) and low in fermentable sugars. Thus, sorghum malt possibly could be used to produce novel low-alcohol beers.