Assessing sweet sorghum juice and syrup quality and fermentation efficiency

Sweet sorghum is a C4 crop with high photosynthetic efficiency with a unique ability of high carbon assimilation (50 g m-2 day-1) and accumulates high concentrations of easily fermentable sugars (glucose, fructose and sucrose) in the stalks. Hence, it is widely believed that it is an alternate energy source that is renewable, sustainable, efficient, cost-effective, convenient and safe to use. Sucrose is the major sugar in sweet sorghum juice which constitutes up to 85% of the total sugars (Woods 2000). The sugar yields ranged between 1.6 to 13.2 Mg ha-1, with significant variations observed between years and regions (Jackson et al. 1980; Reddy et al. 2007; Zhao et al. 2009). The juice sugar content is dependent on the crop stage, because fructose is more abundant at the early development stage, whereas sucrose tends to be dominant after heading (Sipos et al. 2009). The sweet sorghum juice sugar content ranged from 10 to 25 Brix% at maturity (Reddy et al. 2007; Ritter et al. 2004). Research at the International Crops Research Institute for the Semi-Arid-Tropics (ICRISAT) showed that sweet sorghum juice yield ranges between 16.8 to 27.2 m3 ha-1 (Reddy et al. 2007) and accrues about 23% additional returns vis-à-vis grain sorghum (Rao et al. 2009)