Extractability, structure and molecular weight of β-glucan from Canadian rye (Secale cereale L.) whole meal

Oat and barley (1 -> 3)(1 -> 4)-beta-D-glucans (beta-glucan) are readily extracted by hot water but rye beta-glucan is resistant to such extraction. This poor extractability might be due to entrapment within a matrix of arabinoxylan (AX) cross-linked through phenolic constituents. AX are the major nonstarch polysaccharides of the rye kernel. In this study, several approaches were compared in an effort to determine optimum conditions for extraction of high yields, high molecular weight (MW), and high purity of beta-glucan from Canadian rye whole meal. Variables investigated included sodium hydroxide concentrations, extraction time, sample prehydration, extraction under low temperature, and prior extraction of AX with barium hydroxide. There was a linear relationship between the strength of NaOH and amount of beta-glucan extracted and because MW was essentially the same up to 1.0N NaOH, this extraction agent, at room temperature for 90 min, was selected to isolate rye beta-glucan. The beta-glucan was then purified and structure and molecular weight distribution studied.