Optimum steeping process for wet milling of sorghum

Pioneer 8500, a red bud sorghum hybrid, was steeped batchwise using three s teeping solutions at 50 degrees C: SO2 solution; SO2 solution containing 1. 25% (w/w) of a commercial multiple-enzyme preparation (Novo SP249); and SO2 solution with the addition of 0.5% (w/w) lactic acid. Novo SP249 contained pectolytic, cellulolytic, hemicellulolytic, and proteolytic activities and small, amounts of saccharolytic activities. Three SO2 concentrations (0.1, 0.2, and 0.3% w/v) prepared by dissolving sodium bisulfite in distilled wa ter and three steeping times (24, 36, and 48 hr) were used. Incorporation o f multiple enzymes into the SO2 resulted in an increase in starch yield wit h reduced protein content compared with the SO2 solution alone. The best we t-milling performance for sorghum resulted from the SO2 solution containing 0.5% lactic acid; it produced the whitest starch with the highest yield an d the lowest protein content. Both higher SO2 concentration of the steeping solution and longer steeping time led to higher starch yield, lower protei n content in starch, and whiter starch. However, no significant differences in starch yield. protein content in starch. and starch color occurred betw een SO2 concentrations of 0.2 and 0.3% for all three steeping solutions. Th e optimum steeping process for wet milling of sorghum was using a 0.2% SO2 solution with 0.5% lactic acid for 36 hr at 50 degrees C. Under these condi tions. the starch yield, protein content in starch, and L value of starch c olor were 60.2% (db), 0.49% (db), and 92.7, respectively, which were not si gnificantly different from the best values from the 48-hr steeping using th e solution with 0.3% SO2 and 0.5% lactic acid.