Production of Malt-based Sugar Syrup from Enzymatic Hydrolysis of Malted Sorghum and Millet Grains

Abstract

The suitability of sorghum and millet grains in the production of malt-based syrups was determined. The grains were steeped for 50 h, germinated for 5 days at room temperature and were kilned for 48h to produce the malts. Mashing was carried out by three-stage decoction method and the resulting wort further hydrolysed with glucoamylase enzyme to yield malt syrups. Proximate analysis results showed that the crude protein contents in sorghum (11.3%) and millet (10.8%) malts were significantly (p < 0.05) higher than in sorghum (10.36) and millet (8.58%) grains. Cereal grains (sorghum, millet) were higher in fat (6.83, 7.30%), ash (2.41 and 3.16%), fibre (3.31 and 2.63%), moisture (9.93 and 9.95%) and total carbohydrate (71.63 and 53.35%) contents when compared with the malts. Results for malting characteristics of the grains showed that sorghum had significantly (p < 0.05) higher germinative energy (82.53%), germinative capacity (90.50%) diastatic power (32°L) and lower malting loss (13.50%) than millet grains: 76.6%, 85.67%, 27°L and 18.47% respectively. Mashing temperature and pH optima results for amylase activity were 60-70°C in sorghum, 40-450C in millet and pH 6-7 in sorghum and millet respectively. Results obtained on the analysis of the malt syrup samples (sorghum and millet) were (%): Moisture (12.35, 13.46), ash (0.02, 0.04), pH (4.5, 5.0), total solids (82.20, 80.1), Dextrose equivalent (85, 81) and reducing sugar (70.30, 65.45) respectively. Viscosity, colour and taste of the end products were physically checked. Sorghum grain exhibited better potential for syrup production.