Molecular and conformational properties of hemicellulose fiber gum from dried distillers grains with solubles.

Hemicellulose fraction from dried distillers grains with solubles (DDGS) was isolated and its molecular structural and conformational properties were elucidated by using partial acid hydrolysis, methylation analysis and NMR spectroscopy. Using 0.3 M sodium hydroxide (120 °C), a purified water soluble hemicellulose molecules (HFG) was isolated from de-oiled and de-starched DDGS. The yield of HFG was up to 27% (w/w). Results from monosaccharide composition, methylation analysis indicated that HFG comprised three types of sugar residues: arabinose based sugar residues including t-Ara f (28.6 mol%) and 1,3-Ara f (4.9 mol%); xylose based sugar residues including t-Xyl p (14.1 mol%), 1,4-Xyl p (18.6 mol%), 1,3, 4-Xyl p (20.8 mol%), and 1,2,3,4-Xyl p (6.8 mol%); and galactose based sugar residue including t-Gal p (6.1 mol%). Partial acid hydrolysis combined with high performance size exclusion chromatography (HPSEC) indicated that protein (4.69%) was covalently linked with carbohydrate portion in HFG, which can be potentially used as food emulsifiers. Although HFG had a high substitution degree (75%), it was a more rigid molecule compare to gum arabic, indicating a shorter branching chain of HFG. 1D and 2D NMR spectroscopy confirmed the presence of t-xyl p , 2,3,4-β-D-xyl p, t-α-L-ara f , 3-α-L-ara f and 4-β-D-xyl p and several linkage fragments were deduced: t-ara f →2-ara f →2- O -(1,2,3,4-xyl), t-ara f →2-ara f →3- O -(1,2,3,4-xyl), t-ara f →2-ara f →3-ara f and t-gal→2-ara. The information gained from this study could help us to better understand the properties of hemicellulose and its performance in applications. [ABSTRACT FROM AUTHOR]