In vitro Polymerisation of High and Low Molecular Weight Glutenin Subunits with Molecular Oxygen

Abstract

None of the oxidation conditions in previous work on polymerisation of wheat glutenin subunits with inorganic oxidants allowed for complete polymerisation. We here investigated the polymerisation efficiencies of molecular oxygen (slow-acting oxidant), and potassium iodate (fast-acting oxidant). On a small scale, both polymerised the glutenin subunits very efficiently under the conditions used. Only low levels of residual monomer were left in polymerised glutenin subunit mixtures and the resulting polymers were almost exclusively of very high molecular weight. Oxygen was used in further preparative scale polymerisation. Up-scaling lowered the polymerisation efficiency and also resulted in the formation of lower molecular weight polymers. Similarly to observations in small scale polymerisation, low molecular weight glutenin subunits polymerised more efficiently than high molecular weight glutenin subunits. Preparative scale polymerisation of high and low molecular weight subunits and subsequent addition of the resulting mixture to a base flour decreased both maximum resistance and extensibility. Because the oxidised subunits contained a high level of insoluble polymer, the decrease in maximum resistance upon polymer addition was unexpected. A well-defined reason for the dough weakening effect of the polymer cannot be given.