Submitted to: Journal of Cereal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2009
Publication Date: 5/1/2010
Citation: Yan, S., Wu, X., Dahlberg, J., Bean, S., Macritchie, F., Wilson, J.D., Wang, D. 2010. Properties of Field-Sprouted Sorghum and Its Performance in Ethanol Production. Journal of Cereal Science. 51(3):374-380. Interpretive Summary: A common problem among cereal grains is that of pre-harvest sprouting which can occur when mature grain crops are exposed to high levels of rain while still in the field. The high levels of moisture cause the grains to sprout which alters the kernel structure and generally decreases the value of the grain for most typical uses. This project was undertaken to look at the effect of pre-harvest (or field) sprouting of sorghum on its use in ethanol production. Field sprouted samples were found to ferment about 50% faster than non-sprouted sorghum. The amount of ethanol produced from the sprouted sorghum was similar to that of non-sprouted grains. This means that field sprouted sorghum can be used effectively in ethanol production and sorghum grain damaged by field sprouting would still have value.
Technical Abstract: The objective of this research was to investigate physicochemical and biochemical characteristics of field-sprouted grain sorghum and their fermentation performance in ethanol production. Five field-sprouted grain sorghum varieties, which received abnormally high rainfall during harvest, were used in this study. Enzyme activities, microstructure, and flour pasting properties of field-sprouted grain sorghum were analyzed with the Megazyme ceralpha method, scanning electron microscopy, a rapid visco analyzer, and a Brabender visco-amylo-graph. The single kernel characterization system was used to measure kernel hardness, kernel weight, and kernel size. Flour particle size and distribution were measured with a particle size analyzer. The effect of germination (i.e., sprouting) on conversion of grain sorghum to ethanol was determined by using a laboratory dry-grind ethanol fermentation procedure. High performance liquid chromatography was used to determine ethanol concentration and monitor glucose consumption during sorghum fermentation. Germinated sorghum had increased alpha-amylase activity; degraded starch granules and endosperm cell walls; decreased kernel hardness, kernel weight, kernel size, and particle size; and decreased pasting temperature and peak and final viscosities compared with non-germinated grain sorghum. Time required for germinated sorghum to complete fermentation was only about half that of non-germinated sorghum. Also, ethanol yield and fermentation efficiency were similar for sprouted and non-sprouted sorghums.