Determination of high molecular weight beta-glucan in wort and beer using a post-column calcofluor flow-injection-analysis (FIA)

To eliminate the influence of maltose. ethanol, low molecular weight beta-glucan and an inhibitor of the calcofluor fluorescence reaction in wort and beer on the measured values of a calcofluor-FIA, a post-column calcofluor-FIA method has been developed using a short-size gel permeation chromatography column (6.0 x 50 mm). A column packed with polyhydroxymethacrylate gel (molecular weight exclusion limit. 100,000) was found to be the most appropriate for this system. This short column allowed rapid and specific measurement of high molecular weight beta-glucan in a few minutes without the influence of the fluorescence inhibitor. maltose and ethanol which have molecular weights of less than 1000 daltons. Because the low molecular weight beta-glucan responsible for the scatter caused by a slight difference in measuring conditions such as temperature. calcofluor concentrations, sample volumes. etc., was separated through the use of the column. the measured values by the post-column calcofluor-FIA method hardly fluctuated under different conditions. Though it has been recognized that dilution of a sample could affect a calcofluor FIA. the new system was not influenced. This also made it possible to measure the beta-glucan content in dark-coloured samples (even over 100 EBC colour units). The measured values by the post-column FIA showed a high correlation (r(2) = 0.993) with those obtained by the enzymatic: method (the McCleary method).