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Published 2022

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Publication details

Journal : Food Hydrocolloids , vol. 127 , 2022

International Standard Numbers :
Printed : 0268-005X
Electronic : 1873-7137

Publication type : Academic article

Contributors : Ballance, Simon; Lu, YuDong; Zobel, Hanne Kristine; Rieder, Anne; Knutsen, Svein Halvor; Dinu, Vlad T.; Christensen, Bjørn E.; Ulset, Ann-Sissel Teialeret; Schmid, Marius; Maina, Ndegwa; Potthast, Antje; Schiehser, Sonja; Ellis, Peter R.; Harding, Stephen Ernest

Research areas

Quality and measurement methods

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Kjetil Aune
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Summary

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 × 103 g/mol. The beta-glucan molecules analysed by these methods were primarily in a random coil conformation as evidenced from individual Mark-Houwink-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.

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