Response surface methodology was used to investigate the influence of the three malting parameters, i.e. degree of steeping, germination time, and temperature on the quality of proso millet malt. Each predictor variable was tested at three levels. Germination times varied from 5, 6, and 7 days, degrees of steeping were 44, 48, and 52%, and germination temperatures were 16, 20, and 24°C. A set kilning temperature of 65°C was used for all malts. A series of malt quality parameters were investigated including extract, apparent attenuation limit, gelatinisation temperature, ␣-amylase activity, ␤-amylase activity, limit dextrinase activity, Kolbach index, ␣-amino nitrogen, viscosity, and colour. The optimal malting program was achieved after the fifth day of germination, 44% degree of steeping, and a 22°C steeping and germination temperature. The obtained values for the amylolytic and cytolytic attributes were 64.8% extract, 1.383 mPa × s viscosity, 76.0% apparent attenuation limit, 111 U /g ␣-amylase activity, and 102 U /g ␤-amylase activity.

J. Inst. Brew. 116(2), 141-150, 2010Proso millet is a gluten-free cereal and is therefore considered a suitable raw material for the manufacturing of foods and beverages for people suffering from celiac disease. The objective of this study was to develop an optimal mashing procedure for 100% proso millet malt with a specific emphasis on high amylolytic activity. Therefore, the influence of temperature and pH on the amylolytic enzyme activity during mashing was investigated. Size exclusion chromatography was used to extract different amylolytic enzyme fractions from proso millet malt. These enzymes were added into a pH-adjusted, cold water extract of proso millet malt and an isothermal mashing procedure was applied. The temperatures and pH optima for amylolytic enzyme activities were determined. The α-amylase enzyme showed highest activity at a temperature of 60°C and at pH 5.0, whereas the β-amylase activity was optimum at 40°C and pH 5.3. The limit dextrinase enzyme reached maximum activity at 50°C and pH 5.3. In the subsequent mashing regimen, the mash was separated and 40% was held for 10 min at 68°C to achieve gelatinisation. The next step in the mashing procedure was the mixture of the part mashes. The combined mash was then subjected to an infusion mashing regimen, taking the temperature optima of the various amylolytic enzymes into account. It was possible to obtain full saccharification of the wort with this mashing regimen. The analytical data obtained with the optimised proso millet mash were comparable to barley wort, which served as a control.