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Cereal Chem 72:406-410  |  VIEW ARTICLE

Reoxidation of High Molecular Weight Subunits of Glutenin.

P. Schropp, H.-D. Belitz, W. Seilmeier, and H. Wieser. Copyright 1995 by the American Association of Cereal Chemists, Inc. 

Reoxidation behavior of high molecular weight (HMW) subunits of glutenin was studied with regard to subunit composition (Rektor cultivar: 5, 7, 9, 10; Apollo cultivar: 2, 6, 8, 12), protein concentration (1, 2, and 3%), solvent composition and pH (2.0 and 8.0), oxidant (KBrO3; KIO3; and O2) and reaction time (0- 20 hr). The characterization of reoxidized products was achieved by the determination of the thiol content, the molecular weight distribution, and the subunit proportions. The results demonstrated that HMW subunits could be reoxidized to polymers with molecular weights up to several million. The different combinations of subunits did not influence the kinetic of oxidation and polymerization, and the proportions of subunits were independent of the degree of polymerization. Yield and molecular weight distribution of polymers were related both to the protein concentration and to the molar ratio of oxidants to thiol groups. Reoxidation with KBrO3 and oxygen proceeded much slower than with KIO3 and led to higher proportions of polymerized proteins. Obviously, more inter- and less intramolecular disulfide bonds were formed by oxidation with KBrO3 and oxygen compared with KIO3. The kinetics of reoxidation with the halates were independent of the pH values, whereas reoxidation with oxygen took place only at pH 8, and not at pH 2. The addition of urea did not affect reoxidation, whereas the addition of sodium dodecyl sulfate prevented any polymerization.

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