Assessing Fermentation Quality of Grain Sorghum for Fuel Ethanol Production Using Rapid Visco-Analyzer

The Rapid Visco-Analyzer (RVA) was used to characterize the pasting proper-ties of 68 sorghum grains with a standard 23-min temperature profile. The results showed a strong linear relationship between ethanol yield and final viscosity as well as setback. Ethanol yield increased as final viscosity decreased. A modified RVA procedure (10 min) with an application 4 alpha-amylase was developed to simulate the liquefaction step in dry-grind ethanol production. There was a remarkable difference in mashing properties among the sorghum samples with the normal dosage of alpha-amylase. The sorghum samples which were difficult to liquefy in the mashing step had much higher peak viscosities than the samples that were easily liquefied. The results also showed that the relationship between conversion efficiency and mashing property was significant. Tannins cause high mash viscosities. There was a strong linear relationship between tannin content and final viscosity as well as peak viscosity. The modified RVA procedure is applicable not only for characterization of mashing properties but also for optimization of alpha-amylase doses for starch liquefaction.