Isolation, Fractionation, and Structural Characteristics of Alkali‐Extractable β‐Glucan from Rye Whole Meal

The main nonstarch polysaccharide of rye is arabinoxylan (AX), but rye contains significant levels of (1→3)(1→4)‐β‐ d ‐glucan, which unlike oat and barley β‐glucan, is not readily extracted by water, possibly because of entrapment within a matrix of AX cross‐linked by phenolics. This study continues objectives to improve understanding of factors controlling the physicochemical behavior of the cereal β‐glucans. Rye β‐glucan was extracted by 1.0 N NaOH and increasing concentrations of ammonium sulfate were used to separate the β‐glucan from AX and prepare a series of eight narrow molecular weight (MW) distribution fractions. Composition and structural characteristics of the isolated β‐glucan and the eight fractions were determined. High‐performance size‐exclusion chromatography (HPSEC) with both specific calcofluor binding and a triple detection (light scattering, viscometry, and refractive index) system was used for MW determination. Lichenase digestion followed by high‐performance anion exchange chromatography of released oligosaccharides, was used for structural evaluation. The overall structure of all fractions was similar to that of barley β‐glucan.