Short communication: Relationship of carbohydrate molecular spectroscopic features to carbohydrate nutrient profiles in co-products from bioethanol production.

The objective of this study was to use diffuse reflectance infrared Fourier transform (DRIFT) molecular spectroscopy to investigate the relationship between carbohydrate (CHO) molecular structure spectral profiles (in terms of CHO molecular spectral peak area and height intensities) and CHO chemical profiles, CHO subfractions, energy values, and rumen fermentable organic matter supply in different grains and different types of dried distillers grains with solubles. The various CHO molecular spectral bands included A_Cell (peak area region and baseline ∼1485-1188 cm(-1)), mainly associated with hemicellulosic and cellulosic compounds; A_1240 (peak area centered at ∼1240 cm(-1) with region and baseline ∼1292-1198 cm(-1)), mainly associated with cellulosic compounds; A_CHO (peak region and baseline ∼1187-950 cm(-1)) associate with total CHO; A_928 (peak area centered at ∼928 cm(-1) with region and baseline ∼952-910 cm(-1)); and A_860 (peak area centered at ∼860 cm(-1) with region and baseline ∼880-827 cm(-1)), mainly associated with nonstructural CHO; H_1415 (peak height centered at ∼1415 cm(-1) with baseline ∼1485-1188 cm(-1)); and H_1370 (peak height at ∼1370 cm(-1) with a baseline ∼1485-1188 cm(-1)), mainly associated with structural CHO. No significant correlations were found among A_Cell, A_CHO, H_1415, and H_1370 with CHO chemical and nutrient profiles in the bioethanol co-products. However, CHO molecular spectral intensities of A_1240, A_928, and A_860 were strongly correlated with rapidly degradable CHO fraction (CB1), lowly degradable CHO fraction (CB2), and an unavailable CHO fraction (CC) and could be good indicators. In conclusion, the changes in CHO molecular structures during the processing for bioethanol production were highly associated with carbohydrate degradable subfractions in ruminants.