Improvement of sorghum malt saccharification

Abstract

Sorghum malt has low levels of beta-amylase, and worts produced from it have low attenuation limit and do not ferment to the same extent as worts from barley malt. Sorghum beers are consequently low in alcohol. This study explored the feasibility of improving sorghum wortsaccharification by the partial replacement with malted rice.

Samples of each of three sorghum varieties and paddy rice were germinated for five days, by following standard procedures. They were kilned and devegetated. Hot water extracts of sorghum malts alone and mixtures with rice malts (80:20) were obtained using standard procedures of wort extraction.

The pH and turbidity of the wort were determined using pH and Turbidity meters respectively. The attenuation limit was determined using standard procedures. Ninhydrincolourimetric method was used to determine free amino nitrogen (FAN) of the worts.

The pHs of wort from the three sorghum varieties were 5.39, 5.18 and 5.07 for kapaala, kadaga and Global 2000 respectively. Substitution of sorghum malt with rice malt at 20% showed changes in the pH turbidity, and FAN of worts extracted from all three varieties. Starch in the worts in which sorghum malt was supplemented with 20% malted rice was degraded completely to sugars and limit dextrines. Attenuation limits of the worts increased to over 80% with the addition of rice malt, indicating that the worts have a normal composition of fermentable sugars.