395 In vitro polymerisation of wheat glutenin subunits.

W. S. VERAVERBEKE (1), O. R. Larroque (2), F. Békés (2), and J. A. Delcour (1). (1) K. U. Leuven, Laboratory of Food Chemistry, Belgium; (2) CSIRO, Plant Industry, North Ryde, NSW 2113, Australia.

High (HMW-GS) and low molecular weight glutenin subunits (LMW-GS) were isolated from wheat flour and polymerised both separately and in a mixture with different inorganic oxidising agents (KBrO(3), KIO(3), H(2)O(2)). Changes in size distribution were evaluated with size-exclusion high performance liquid chromatography, multi-layer sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and flow-field flow fractionation. Multi-layer SDS-PAGE allowed for a simultaneous evaluation of changes in relative proportions of different glutenin subunits. Flow-field flow fractionation was particularly suitable for measuring changes in glutenin size in the very high molecular size ranges. The different oxidising agents produced different size glutenin polymers when used at equivalent levels. However, with none of the oxidation conditions, a complete polymerisation of HMW-GS was achieved. Interestingly, high concentrations of KIO(3) negatively affected the degree of polymerisation. A similar observation was not made with KBrO(3) or H(2)O(2). Multi-layer SDS-PAGE of remaining monomers during polymerisation showed a higher degree of incorporation of x-type HMW-GS and B-LMW-GS than of y-type HMW-GS and C-LMW-GS, respectively.