ARS | Publication request: Calcofluor fluorescence assay for wort beta-glucan in a microplate format

Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 12, 2008
Publication Date: January 15, 2009
Citation: Schmitt, M., Budde, A.D. 2009. Calcofluor Fluorescence Assay for Wort Beta-Glucan in a Microplate Format. Cereal Chemistry. 86(1):33-36.

Interpretive Summary: Beta glucans are carbohydrates that are present in both barley grain and the malt that is produced from the grain by controlled germination or malting. Beta glucans are present in a number of other cereals (including oats) and cereal products, and have been associated with certain healthful benefits. However, beta glucans that are released from malt during brewing interfere with necessary filtration steps, and thus cause substantial practical problems in the brewing process. As a result, low levels of beta-glucans are desired in worts (brewing extracts made from malt). Low levels of beta-glucans are a very desirable feature of barley genotypes that are to be used for malting and in brewing. The levels of beta-glucans in worts from barley germplasm being evaluated for use in malting are commonly determined by measuring the fluorescence resulting from an interaction of beta-glucans with Calcofluor, a common fluorescent brightener used in many laundry detergents and additives. However, the instrumentation most often used to measure the beta-glucan fluorescence is expensive and not widely available. The method presented in this note describes a way to modify the routine Calcofluor analysis of wort beta-glucan to be able to use less expensive and more widely available fluorescent microplate reader instruments for routine beta-glucan measurement in those laboratories where the more expensive instrumentation is not available.

Technical Abstract: The widely-used fluorescent (Calcofluor) flow injection analysis method for determining the concentrations of beta-glucans in Congress worts from barley malts is adapted to microplate format. Adaptation of the Calcofluor assay to use widely available fluorescent microplate readers makes the assay more readily available to research laboratories lacking access to the dedicated flow injection analysis systems. The microplate format for the assay yields comparable results to the flow injection system for both ASBC malt check analysis samples as well as a selection of diverse barley lines that vary widely in their malting quality attributes. In addition, the microplate assay is readily adaptable to more complex analyses, including inclusion of internal beta-glucan standard additions to worts, allowing calculation of and correction for wort-dependent sample quenching.