Fermentation performance of current Australian sorghum varieties

Sorghum is an important raw material for the production of Baijiu - a major distilled spirit produced and consumed in China. Baijiu typically has an ethanol content of 40-60 vol% and is most often consumed neat. This Chinese grain liquor is the most-consumed spirit in the world, and has the highest-value market by turnover. Baijiu is produced in very large quantity in China with Sichuan, Guizhou, Shandong, Jiangsu, Anhui and Henan provinces collectively claimed to produce more than 90% of the total liquor output. This represents a potentially large and valuable market for Australian sorghum. This study investigates the effects of different Australian sorghum varieties on ethanol fermentation performance. Major commercial sorghum varieties (13) were fermented using a dry-grind method. These varieties were reported previously to have significantly different field performance and physico-chemical properties. Fermentation profile of most varieties was similar, with a lag phase in the first 12 hours, followed by an exponential phase till 60-80 hours and finally a stationary phase. Fermentability of all varieties was in the range of 87.3-89.1%. Final alcohol content was strongly correlated to seed protein content (R2=0.6563), but weakly correlated to starch content (R2=0.3111), glucose content (R2=0.2407) and whole grain gross energy (R2=0.2926). Yeast assimilable nitrogen content was not correlated with fermentation rate when comparing different sorghum varieties. The outcome of this study enables systematic comparison of Australian sorghum for alcohol production and paves the way for further study into solid state fermentation of sorghum under simulated conditions for Baijiu production.