Publication no. C-2000-0814-01R |  VIEW ARTICLE

In Vitro Polymerization of Wheat Glutenin Subunits with Inorganic Oxidizing Agents. II. Stepwise Oxidation of Low Molecular Weight Glutenin Subunits and a Mixture of High and Low Molecular Weight Glutenin Subunits.

Wim S. Veraverbeke (1,2), Oscar R. Larroque (3), Frank Békés (3), and Jan A. Delcour (1). (1) Laboratory of Food Chemistry, Katholieke Universiteit Leuven, Kardinaal Mercierlaan 92, B-3001, Heverlee, Belgium. (2) Corresponding author. Phone: +32-16-321634. Fax: +32-16-321997. E-mail: <wim.veraverbeke@agr.kuleuven.ac.be> (3) Grain Quality Research Laboratory, CSIRO Plant Industry. P.O. Box 7, North Ryde, NSW 1670, Australia. Cereal Chem. 77(5):589-594. Accepted May 15, 2000. Copyright 2000 American Association of Cereal Chemists, Inc.

High and low molecular weight glutenin subunits (HMW-GS and LMW-GS) were isolated from wheat flour. LMW-GS and a 1:2 (w/w) mixture of HMW-GS and LMW-GS were polymerized in vitro at pH 3.0 by stepwise oxidation with different oxidants (KBrO(3), KIO(3), H(2)O(2)). In analogy with the oxidation of HMW-GS, KBrO(3) produced smaller polymers for LMW-GS than KIO(3) or H(2)O(2). While similar average sizes were found with flow-field flow fractionation for LMW-GS polymerized with KIO(3) and H(2)O(2), multilayer SDS-PAGE and size exclusion HPLC indicated that size distributions were different. Significantly fewer monomers remained after polymerization of LMW-GS than with HMW-GS. The higher polymerization efficiency of LMW-GS was also obvious during polymerization of a mixture of HMW-GS and LMW-GS. Mixed polymerization of HMW-GS and LMW-GS had no observable effect on the polymer size. Multilayer SDS-PAGE of remaining monomers during polymerization revealed differences in polymerizing efficiency between structurally different glutenin subunits, with x-type HMW-GS and B-LMW-GS showing higher degrees of incorporation than y-type HMW-GS and C-LMW-GS, respectively.