Impact of Redox Agents on the Extractability of Gluten Proteins during Bread Making

The gluten proteins gliadin and glutenin are important for dough and bread characteristics. In the present work, redox agents were used to impact gluten properties and to study gliadin−glutenin interactions in bread making. In control bread making, mixing increased the extractability of glutenin. The level of SDS-extractable glutenin decreased during fermentation and then further in the oven. The levels of extractable α- and γ-gliadin also decreased during bread baking due to gliadin−glutenin polymerization. Neither oxidizing nor reducing agents had an impact on glutenin extractabilities after mixing. The redox additives did not affect ω-gliadin extractabilities during bread making due to their lack of cysteine residues. Potassium iodate (0.82−2.47 μmol/g of protein) and potassium bromate (1.07−3.17 μmol/g of protein) increased both α- and γ-gliadin extractabilities during baking. Increasing concentrations of glutathione (1.15−3.45 μmol/g of protein) decreased levels of extractable α- and γ-gliadins during baking. The work not only demonstrated that, during baking, glutenin and gliadin polymerize through heat-induced sulfhydryl−disulfide exchange reactions, but also demonstrated for the first time that oxidizing agents, besides their effect on dough rheology and hence bread volume, hinder gliadin−glutenin linking during baking, while glutathione increases the degree of covalent gliadin to glutenin linking. Keywords: Bread making; wheat gluten; gliadin−glutenin interaction; protein extractability