Trends in Starch and Sucrose Content among Sweet Sorghum Genotypes and Implications for Sucrose and Ethanol Production

Sweet sorghum has been suggested as a feedstock into the sugarcane mills for sucrose production in Zimbabwe and Swaziland. Sweet sorghum is widely grown by subsistence farmers and matures in 3 to 6 months in February, March and April, before sugarcane harvesting begins. Sweet sorghum has low sucrose content that is difficult to extract during processing. The hypothesis of the study was that sweet sorghum was a potential feedstock to sugarcane mills for the production of sugar and ethanol. The objective of this study was to investigate the trends in starch and sucrose content of four sweet sorghum genotypes namely M337, M81-E, Theis and Topper, and evaluate the potential of sweet sorghum as a feed stock for sugar and ethanol production. The sorghum juice was collected on August 10. August 24. September 8. September 18 and October 2. 2006 and starch and sucrose content were determined. There were significant (P＜0.001) genotypes by sampling date interaction effect s. Both starch and sucrose content increased with crop sampling date. Genotypes M337 and Theis were late maturing for sucrose content compared to M81-E and Topper. All genotypes except M337 produced no significant increase in starch after 101DAP. Trend s in sucrose and starch content were similar, indicating the reason sucrose was difficult to extract from sweet sorghum. The impact of this study would be boosting the incomes of small scale growers who would be subcontracted by the sugar mills to produce sweet sorghum as a feedstock to the mills before sugarcane mature s.