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Gewählte Publikation:

Ballance, S; Lu, YD; Zobel, H; Rieder, A; Knutsen, SH; Dinu, VT; Christensen, BE; Ulset, AS; Schmid, M; Maina, N; Potthast, A; Schiehser, S; Ellis, PR; Harding, SE.
(2022): Inter-laboratory analysis of cereal beta-glucan extracts of nutritional importance: An evaluation of different methods for determining weight-average molecular weight and molecular weight distribution
FOOD HYDROCOLLOID. 2022; 127, 107510 FullText FullText_BOKU

Abstract:
In an interlaboratory study we compare different methods to determine the weight-average molecular weight (Mw) and molecular weight distribution of six cereal beta-glucan isolates of nutritional importance. Size exclusion chromatography (SEC) with multi-angle light scattering (MALS), capillary viscometry, sedimentation velocity analytical ultracentrifugation and one asymmetric flow field-flow fractionation (AF4)-MALS method all yielded similar Mw values for mostly individual chains of dissolved beta-glucan molecules. SEC with post-column calcofluor detection underestimated the Mw of beta-glucan > 500 x 10(3) g/mol. The beta-glucan molecules analysed by these methods were primarily in a random coil conformation as evidenced from individual MarkHouwink-Kuhn-Sakurada (MHKS) scaling coefficients between 0.5 and 0.6 and Wales-Van Holde ratios between 1.4 and 1.7. In contrast, a second AF4-MALS method yielded much larger Mw values for these same samples indicating the presence and detection of beta-glucan aggregates. Storage of the six beta-glucan solutions in the dark at 4 C for 4 years revealed them to be stable. This suggests an absence of storage-induced irreversible aggregation phenomena or chain-scission. Shear forces in SEC and the viscometer capillary and hydrostatic pressure in analytical ultracentrifugation probably led to the reversable dissociation of beta-glucan aggregates into molecularly dissolved species. Thus, all these methods yield true weight-average molecular weight values not biased by the presence of aggregates as was the case in one of the AF4 based methods employed.
Autor*innen der BOKU Wien:
Potthast Antje
Schiehser Sonja
BOKU Gendermonitor:


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Dietary fibre
Light scattering
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