Redox Reactions in Wheat Dough as Affected by Ascorbic Acid

Dough rheology and bread quality of supplemented flours Reología de la masa y calidad del pan de harinas suplementadas

“…The larger W and P changes occurred into samples added with glutathione at the highest concentration. These results were to be expected since glutathione behaves as a reducing agent and is able to cause ruptures of disulfide cross-links by SH/SS interchanges (Grosch & Wieser, 1999), thus reducing the mean molecular weight of glutenins and inducing changes in the gluten structure and in the balance between viscous and elastic properties (G 0 decreases more rapidly than G 00 ) (Berland & Launay, 1995). The addition of both an oxidative enzyme, such as glucose oxidase and the ascorbic acid determined the opposite effect.…”

“…The strengthening action of glucose oxidase (especially at the highest concentration) was related to the hydrogen peroxide produced during reaction that promoted the formation of disulphide linkages in gluten protein (Poulsen & Hostrup, 1998). The mechanism proposed for the improver action of the ascorbic acid (L-threo-ascorbic acid, in particular) is based on the assumption that the dehydroascorbic acid formed inhibits the cleavage of the intermolecular SS bonds of gluten proteins that happens in presence of reduced glutathione (Grosch & Wieser, 1999). The rate of L-threo-ascorbic acid oxidation in dough depends on the amount of oxygen kneaded into dough.…”

“…In particular, the improver action of the ascorbic acid is due to its oxidation by gaseous oxygen to dehydroascorbic acid which determines the rapid oxidation of glutathione present in flour thus minimizing the SH/SS interchange reactions of reduced glutathione with intermolecular SS bonds of gluten molecules. These interchange reactions would depolymerise gluten proteins and weaken the dough (Grosch & Wieser, 1999).…”

Production of Thiyl Radical on Soluble Glutenin by Superoxide Anion Radical

“…While it is necessary to bear in mind that a real dough sample is a very complex system and contains several low molecular weight thiols like GSH. Consequently, the possibility that such thiols provide the same products by AsA via recombination of glutathionyl radicals to oxidized glutathiones (Grosch and Wieser, 1999) cannot be ruled out. However, the observed occurrence of S• (induced by O 2 − ) in soluble glutenin can be extrapolated to wheat protein in real dough samples, resulting in the formation of SS bridges between wheat proteins.…”

“…In this process, DHA is reduced back to AsA by glutathione dehydrogenase in conjunction with the oxidation of reduced glutathione (GSH). It is precisely oxidized glutathione that, in turn, increases the formation of disulfide (SS) bridges in wheat proteins through a SS-sulfhydryl (SH) exchange reaction, generating a network structure in the dough and an improvement in loaf structure as a result (Sarwin et al, 1993;Hahn and Grosch, 1998;Grosch and Wieser, 1999;Koehler, 2003).…”