Enzymatic method for determination of (1-->3)(1-->4)-beta-D-glucans in grains and cereals: collaborative study

The McCleary enzymatic assay for mixed linkage (1-->3)(1-->4)-beta-D-glucans has been modified to apply to oat and barley fractions and ready-to-eat (RTE) cereals. The proposed method involves lower sample concentrations; stirring the samples; a longer, warmer lichenase digestion; and longer beta-glucosidase digestion. These changes result in higher recovery of beta-glucan. This modification expands on the American Association of Cereal Chemists (AACC) Method 32-22 by the addition of a desugaring procedure, which is necessary for RTE cereals. Results from collaborative studies sponsored by AACC and AOAC demonstrate good precision for an enzymatic assay. The average relative standard deviation for reproducibility (RSDR, a measure of interlaboratory variation) for 20 oat, barley, and cereal samples was 9.7%. The average RSD for repeatability (RSDr, intralaboratory variation) was 5.0%. The enzymatic method has been adopted first action by AOAC International for determination of beta-glucans in oat and barley fractions, and ready-to-eat cereals.