Rapid determination of high molecular weight 1,3/1,4-beta-D-glucan by a novel photometric method

Analytical Session
Liisa P Otama, Thermo Fisher Scientific, Vantaa, Finland
Co-author(s): Liisa Otama, Sari Hartikainen, and Annu Suoniemi-Kahara, Thermo Fisher Scientific, Vantaa, Finland

ABSTRACT: In the beer malting and brewing process, one important analyte is beta-glucan. Beta-glucans are polysaccharides of D-glucose monomers linked by beta-glycosidic bonds. Beta-glucans are present in the cell walls of cereals and are capable of clogging process filters. Excessive amounts of beta-glucan may cause haze in the end product and impair the taste of beer. For these reasons it is important to determine the concentration of beta-glucan, in particular the part of the beta-glucan polymer that has a molecular mass of about 10,000 Da or more. The aim of this study was to provide a robust automated photometric analysis method that is suitable for liquid samples derived from processing of cereals. A rapid two reagent method was developed for automated discrete analyzers. The method is easily adapted to a manual spectrophotometer as well. The use of blank buffer eliminates sample color interference. In preliminary testing of beer and wort samples, this method correlates well with the results obtained by a fluorometric method using Calcofluor fluorescence dye. The Calcofluor method is recommended by the European Brewery Convention in EBC Methods 8.13.2, 4.16.2, and 3.10.2 and by the American Society of Brewing Chemists in ASBC Method Wort-18. Thus, this study presents an alternative rapid method especially suitable for routine use. A method performance study was done by Thermo Scientific Gallery and Arena discrete analyzers at wavelength of 405 nm. Method linearity was determined between 15 and 500 mg/L with aqueous beta-glucan standard solutions. Beer and wort samples tested showed excellent repeatability and reproducibility, with typical variation being 2% or less. Total analysis time for 9 samples with 10 replicates (total 90 results) was less than 40 min. As an improvement on the existing fluorometric method, the open on-board stability of these novel non-hazardous reagents was tested to be at least 30 days.

Sari Tikanoja received a Ph.D. degree in biochemistry from Kuopio University, Finland, in 1991. She started her professional career in clinical laboratories and has a diploma of hospital laboratory management. In 1989, she became R&D director in Medix Biochemica, a Finnish company producing monoclonal antibodies and products thereof. In 2007 she joined Thermo Fisher Scientific Finland, a provider of automated analytical instruments and systems for clinical, environmental, and industrial markets. She started as a senior manager and in 2009 became R&D director, diagnostics.