DIETARY FIBER REAGENT QUALITY AND PURITY
Reagent Quality
When performing analytical tests for nutrition facts labelling purposes, the reliability and accuracy of the results obtained is clearly of paramount importance.  Unfortunately, the choice of commercial supplier for the reagents required to conduct total dietary fiber measurement can have a profound impact on the results obtained. This issue was recently highlighted in a peer-reviewed journal, Cereal Chemistry, 2013, 90(4), p396-414.
It was discovered that some commercially available amyloglucosidase enzyme preparations routinely used in DF determination are highly contaminated with β-glucanase (cellulase). This contamination can lead to depolymerisation of β-glucan and therefore to an underestimation of dietary fiber in β-glucan-containing grains, food products, and ingredients. The level of β-glucamyloglucosidase purityanase contamination present in the amyloglucosidase preparations currently offered by Sigma-Aldrich and Biosentec can be clearly demonstrated by viscometry with Medium-Viscosity Barley β-Glucan as substrate. The viscosity of the β-glucan solution was reduced rapidly over time upon incubation with amyloglucosidase containing the β-glucanase impurity in the case of the Sigma-Aldrich and Biosentec amyloglucosidase products, while the Megazyme amyloglucosidase product, containing virtually no β-glucanase contamination, had little or no effect on the viscosity. The catalogue and lot numbers of the three products used in this analysis were 1) Megazyme, Cat. # E-AMGDF, Lot #51002; 2) Sigma Chemical Company, Cat. # A9913-10ML, lot#119K8719 and 3) Biosentec, Cat. #32C, Lot #11181.
This β-glucanase contamination can also be shown by performing incubations of amyloglucosidase with β-Glucazyme tablets, a specific substrate for the measurement of enzymes active on mixed linkage β-glucans, with the same results – irrefutable evidence of β-glucanase contamination in the Sigma-Aldrich and Biosentec products and confirmation of the purity of Megazyme’s amyloglucosidase offering.
This information will cause grave concern for food manufacturers as not only is β-glucan the most common source of dietary fiber in food, it is also the only dietary fiber ingredient for which a health claim can be made in the United States under rule change 21 CFR Part 101 currently proposed by FDA and expected to be enacted by 2016. Furthermore, underestimation of β-glucan automatically leads to an underestimation of total dietary fiber and could in some cases result in a food product falling short of the dietary fiber content required to make a nutrient content claim. For more information on the regulation of dietary fiber with regards to nutrition facts labelling, see Megazyme’s section on regulation.