Sugar Stability of Sweet Sorghum Exposed to Climate Controlled and Ambient Storage Conditions

Abstract

Historically, crop based ethanol has predominantly been achieved in the United States through starch-based and sugar-based conversions. With corn being one of the leading food and feed crops in the United States, and sugarcane’s inability to adapt to U.S. production regions, Sorghum (Sorghum bicolor L. Moench) has been identified as a potential alternative biofuel feedstock. The objective of this study was to evaluate the stability of non-structural carbohydrates (sugar) present in sweet sorghum juice, by tracking the sugar degradation of ‘Dale’ and ‘M81E’ while exposed to extended periods of climate controlled and ambient conditions after peak sugar accumulation. The data from both genotypes indicated that sugar yields can be sustained for weeks without significant losses. The plants left in the field for the ambient treatment continued sugar accumulation until photosynthesis and transpiration halted, causing immediate loss in sugar. Samples under the controlled treatment retained sugar yields for 3-4 weeks with minimal losses in yield, followed by a steady reduction for the remainder of the evaluations. However, the overall sugar loss after 70 days was comparable between treatments, which leads to the conclusion that sweet sorghum has the potential to be stored up to four weeks before significant yield loss occurs, regardless of storage methods. Combining staggering sweet sorghum plantings with short-term storage to sugarcane productions makes sorghum a suitable alternative or complementary feedstock to current sugar-based ethanol refineries.