Kupetz, M.; Aumer, J.; Harms, D.; Zarnkow, M.; Sacher, B.; Becker, T.
High-throughput beta-glucan analyses and their relationship with beer filterability
Beer filterability is strongly related to the amount and molar mass distribution of β-glucan. Different commercial quantification methods yield different β-glucan concentrations and beer filterability. In order to acquire detailed information on the measureable molar mass and its impact on beer filtration, six high-throughput methods were developed and analysed. These methods involve three calibration standards (Skandinavisk Bryggeri Laboratorium standard, SBL; Megazyme standard for continuous flow analyser, CFA; and 650 kDa standard) and two dyes (Calcofluor and Congo red). Significant correlation was observed between cellulose nitrate membrane filtration and fluorometrically determined β-glucan content (SBL calibration: r = 0.604, P < 0.001; CFA calibration: r = 0.687, P < 0.001). However, no correlation was observed with the colorimetric methods. Polyethersulphone membrane filtration correlated significantly with specific viscosity (r = 0.710, P < 0.001) and fluorometrically determined β-glucan content (CFA calibration: r = 0.586, P < 0.001). However, there was no correlation between the filtration performance of diatomaceous earth and the established beer properties. No correlation between the developed colorimetric and fluorometric methods was found using the SBL and CFA standards. However, a significant correlation was observed with the 650 kDa standard (r = 0.836, P < 0.001). A wide variation, especially between the dyes, was observed in the measurable β-glucan molar mass distribution determined using field-flow fractionation. Our results demonstrate the impact of method parameters on β-glucan concentration. Thus, known β-glucan thresholds regarding filterability must be reconsidered. We conclude that a valid β-glucan quantification method can provide reliable information on beer filterability.