Ethanol Fermentation Performance of Grain Sorghums with Modified Endosperm Matrices

Abstract

Thirteen sorghum entries (lines and hybrids) with different endosperm matrices have been tested for ethanol production using a laboratory dry grind process in attempting to elucidate the relationship between physical characters, chemical compositions and ethanol fermentation efficiency. Results showed that ethanol fermentation efficiencies were significantly different among the tested samples with waxy and heterowaxy samples having the highest efficiencies. Differential scanning calorimetric (DSC) thermograms showed samples with obvious amylose-lipid complexes peaks had lower fermentation efficiencies and samples with no amylose-lipid complexes peak had high fermentation efficiencies. The R2 between the rapid visco analyzer (RVA) viscosity values and fermentation efficiencies were low (0.230, 0.109, and 0.007 for final, peak, and hold viscosities). The free amino nitrogen (FAN) contents in sorghum samples were positively related with the fermentation rate during fermentation; and the R2 for linear regression between FAN and 24-hour fermentation efficiencies was 0.8618. DDGS from different sorghum had significantly different crude protein and crude fat contents. Residual starch contents in DDGS ranged from 0.60% for high efficient sample to 2.66% for low efficient sample. Amino acid composition of DDGS from those sorghum samples indicated lack of essential amino acids compared to soy proteins.