Wet Milling of Grain Sorghum Using a Short Steeping Period

Commercial yellow grain sorghum was steeped in a vented container at 50-70°C for 2-10 hr with 1.5 parts (by weight) of water containing initially 0.1-0.5% sulfur dioxide (SO 2 ). During steeping, 75% of the SO 2 was lost through the vent. When grain sorghum and dent corn were steeped at 58°C with an initial concentration of 0.25% SO 2 , steepwater uptake by grain sorghum was faster during the first 4 hr, but leveled off at 4% below that of corn after 10 hr. In addition, the steepwater of grain sorghum became 25% more acidic than that of corn after 2-10 hr. The optimum recovery of starch from grain sorghum steeped 4 hr was 51% at 58°C with an initial concentration of 0.3% SO 2 . Decortication of the grain sorghum produced 70% recovery of pericarp-free, broken kernels, which gave a somewhat reduced recovery of milled starch with only a slight improvement in brightness. The hot paste characteristics of the starches from two sample of yellow grain sorghums matched those of a commercial corn starch.