THE EFFECT OF BETA-GLUCAN MOLECULAR-WEIGHT ON THE SENSITIVITY OF DYE BINDING ASSAY PROCEDURES FOR BETA-GLUCAN ESTIMATION

An assay procedure has been developed for quantifying β‐glucan, based upon its reaction with the dye Congo Red. The sensitivity of this method to changes in β‐glucan molecular weight has been determined using β‐glucans prepared from standard material by acid hydrolysis and comparison has been made with a Calcofluor‐based method for quantifying β‐glucans. The Congo Red assay was found to be optimally sensitive to β‐glucans with molecular weights of approximately 2.5 × 105 Daltons, whereas the Calcofluor assay was most sensitive to β‐glucans with molecular weights in excess of 5 × 104 Daltons. The purity of the β‐glucan used during this investigation was determined using an enzyme‐based procedure in which the polysaccharide was degraded to glucose by the addition of β‐glucanase. The β‐glucanase employed was partially‐purified from Trichoderma viride cellulase using a novel batch ion‐exchange method which is also described. 1990 The Institute of Brewing & Distilling