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ARS Home » Southeast Area » New Orleans, Louisiana » Southern Regional Research Center » Commodity Utilization Research » Research » Publications at this Location » Publication #326772

Research Project: Developing Technologies that Enable Growth and Profitability in the Commercial Conversion of Sugarcane, Sweet Sorghum, and Energy Beets into Sugar, Advanced Biofuels, and Bioproducts

Location: Commodity Utilization Research

Title: How the quality and processing attributes of commercial sweet sorghum hybrids and cultivar compare for biorefining

item Eggleston, Gillian
item Wartelle, Lynda
item Zatlokovicz Iii, John
item Petrie, Eric
item Cole, Marsha
item St Cyr, Eldwin

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/1/2017
Publication Date: 6/22/2017
Citation: Eggleston, G., Wartelle, L., Zatlokovicz, J., Petrie, E., Cole, M., St Cyr, E. 2017. How the quality and processing attributes of commercial sweet sorghum hybrids and cultivar compare for biorefining. In: Proceedings for the Advances in Sugar Crop Processing and Conversion Conference, March 15-18, 2016, New Orleans, Louisiana. p. 255-272.

Interpretive Summary:

Technical Abstract: Quality and processing attributes of sweet sorghum (Sorghum bicolor L. Moench) biomass are critical to the development of a large-scale industry for the manufacture of bioproducts. Two commercial sweet sorghum hybrids 105 and 106, later and earlier maturing, respectively, were compared to inbred, later-maturing Top 76-6 cultivar, for agronomic, quality, and processing attributes at the soft dough (SD) and hard dough (HD) physiological maturity stages. Crops were grown in South Louisiana (April to Sept, 2014). Juice was extracted from topped whole-stalks by roller milling, then pilot plant clarified (80 °C; target limed juice pH of 6.5; 5 ppm polyanionic flocculant) and vacuum evaporated to syrups. Crop yields varied (P<0.05) with 105 > Top 76-6 > 106. Hybrid 106 contained a marked amount of auxiliary seed-head/stalk (side-branch tillers) due to early maturing, which reduced growth of the main stalk and detrimentally affected juice sugar content and turbidity, and increased starch. Except for 105 at the HD stage, turbidity removal across clarification was very acceptable (>92%) and directly related to the median size of the starch granules and their percent removal. Clarification was generally better at SD than HD stage. Factors that reduced crop yield also increased syrup viscosity, and starch also contributed to viscosity. The raw juice color was strongly, negatively correlated (R2=0.898) with crop yield, suggesting factors that reduced yield tended to increase color. As positive correlations existed between color and green leaves (R2=0.653) and particularly auxiliary seed-head/stalk (R2=0.852), these tissues which contain chlorophyll must have contributed to the juice color. On the other hand, brown leaves did not contribute to color and, since the top seed-heads were removed before processing, they also did not contribute. There was no genotype or maturity stage variation for assimilable nitrogen, a requirement for fermentation, of raw juice and syrup. Overall, the hybrids processed similarly to cultivar Top 76-6, and 105 had the additional advantages of having low starch and no auxiliary seed-head/stalk.