Quality Attributes of Sweet Sorghum for the Large-Scale Production of Bioproducts: A 1-Year Comparison of Commercial Hybrids and a Cultivar

Quality attributes of sweet sorghum affect the industrial processing of this biomass into biofuels and bioproducts. In a 1-year study, two commercial sweet sorghum hybrids 105 and 106, late and early maturing, respectively, were compared to inbred, later-maturing Top 76-6 cultivar, for quality attributes at the soft dough (SD) and hard dough (HD) maturity stages. Crops were grown in South Louisiana, and juice was extracted from topped whole stalks by roller milling. Crop biomass yields varied (P < 0.05) with 105 > Top 76-6 > 106, with hybrid 106 containing markedly more auxiliary seed head/stalk (side-branch tillers) compared to none in hybrid 105 and only 0.5% in Top 76-6 at HD. For the three genotypes, the stalk contributed between 63.8 and 86.5% of the fresh weight biomass which decreased from SD to HD. The growth parameters of crop yield, and stalk biomass, height, wet weight, first internode diameter, and to a lesser degree hardness of the last internode were strongly, negatively correlated with both soluble and insoluble starch in the raw juice. This suggested that increased growth/maturity of the genotypes tended to reduce starch. Overall, except for significantly (P < 0.05) lower mode values in the hybrids compared to Top 76-6, there were little statistical differences in starch granule size parameters. Further studies are now warranted to ascertain environmental effects on quality.