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Sorghum (Sorghum bicolor L. Moench) is a major cereal crop in tropical Africa, Asia and other regions where draught prevails. However, its usage as human food is greatly limited by its reduced protein digestibility after processing sorghum using either dried or wet steam method. This study was aimed at utilizing the lees by using Koji's solid-substance fermentation to improve protein digestibility of glutinous rice-like sorghum. The results showed that protein digestibility of the uncooked glutinous rice-like sorghum was 65.7% and was reduced to 42% after steaming and was increased to 52.1, 83.9 and 81.4%, respectively, after each of three cycles of solid fermentation-distillation processes. Before cooking, red glume sorghum contained 6.5 mg/g polyphenols, which was reduced to 0.7 mg/g after cooking. Repeated fermentation and distillation of lees increased polyphenol contents from 1.8 to 2.4 and to 4.5 mg/g, respectively, for each of three cycles. Thus, Koji's solid fermentation method might substantially improve nutrient values of sorghum as judged from its in vitro protein digestibility, especially important in underdeveloped Africa as protein source. Other potential utilizations of lees including as a viable feedstock for ethanol production in biofuel industry conforming to environmental green goal are discussed. PRACTICAL APPLICATIONS Sorghum is commonly planted by farmers and consumed as food by humans or as feed to animals in Africa, Asia and the semiarid tropical areas. But there are several factors that reduce protein digestibility after wet steam cooking. The present study demonstrated that after the first cycle of fermentation-distillation process, protein digestibility of lees was increased and the level higher than that of the uncooked sorghum. Koji fermentation of sorghum not only provides rich sources of protein, and its by-product, lees, could be utilized in food and feed industries as well. |
