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Ethanol-Production Performance of Ozone-Treated Tannin Grain Sorghum Flour¹

¹Contribution number 11-346-J from the Kansas Agricultural Experiment Station, Manhattan, KS 66506. ²Department of Biological and Agricultural Engineering, Kansas State University, Manhattan, KS 66506. ³Current address: C. W. Brabender Instruments, Inc., 50 East Wesley Street, South Hackensack, NJ 07606. ⁴Department of Grain Science and Industry, Kansas State University, Manhattan, KS 66506. ⁵United States Department of Agriculture (USDA), Agricultural Research Service, Grain and Animal Health Research Center, Manhattan, KS 66502. Names are necessary to report factually on available data; however, USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be used. ⁶Corresponding author. Phone: (785) 532-2919. Fax: (785) 532-5825. E-mail: dwang@ksu.edu

Ozone has been reported as being able to degrade macromolecules such as cellulose, starch, lignins, and tannins in the textile, pulping, and water-treatment industries. Thus, we hypothesized that ozone treatment may also inactivate tannin activity and increase fermentation efficiency of tannin sorghum lines. The objective of this research was to study the physicochemical properties of ozone-treated whole tannin grain sorghum flour and its fermentation performance in ethanol production. Results showed that the ethanol yields from ozone-treated tannin grain sorghums were significantly higher than yields from the untreated flour. The fermentation efficiency of ozone-treated tannin grain sorghum was approximately 90%, which was 8–14% higher than that of untreated samples at the 36th hr of fermentation. At the end of 72 hr of fermentation, the efficiencies of ozone-treated sorghum flour were 2–5% higher than those of untreated samples. Measured tannin levels of ozone-treated samples decreased significantly from 3.8 to 2.7%. Gel-permeation chromatographic results indicated that both degradation and polymerization processes might have happened to starch molecules during ozone treatment. Rapid Visco Analyzer data showed that the setback of viscosity of ozone-treated flour was lower than that of untreated flours. Distillers dried grains with solubles made from ozone-treated sorghum were low in residual starch (<1%) and high in crude protein (≈35%). Therefore, ozonation could be a novel and useful method to improve ethanol yield and fermentation efficiency of tannin grain sorghum.