Structural characterization of water-insoluble nonstarchy polysaccharides of oats and barley

Water-insoluble dietary fibre of dehulled oat and barley grain was isolated with enzymatic hydrolysis of starch and protein and further extracted sequentially. The extractants used were saturated barium hydroxide, water, 1 M potassium hydroxide and 4 M sodium hydroxide. The fractions were dialysed against pure water, freeze-dried and weighed. Repeatable recoveries of extracts were obtained. The ground grains and extracted fractions were characterized for their fat and protein content. The fractions were hydrolysed and characterized by measuring their neutral sugar composition using gas chromatography. Comparison of the amounts of cellulosic and noncellulosic polysaccharides was made. Further characterization of fractions was performed with solid-state 13C CP/MAS NMR spectroscopy and IR spectroscopy. The differences in composition of insoluble material between oats and barley were small. The distribution of masses and monosaccharides of the five fractions obtained were similar and the measured spectra show the same characteristic signals as saccharide structures.