Disulfide wheat dough

The peculiar viscoelastic properties of wheat dough are the result of the presence of a three-dimensional network of gluten proteins. The network is formed by thiol-disulfide exchange reactions among gluten proteins. Peptide disulfides can interfere in a thiol-disulfide exchange system by reacting with a protein (PR)-thiol to liberate a peptide (R)-thiol and form a mixed disulfide, as follows ... 

Figure 8-30 Schematic Diagram of Bonds Within and Between Polypeptide Chains in Dough. Solid lines represent covalent bonds, dotted lines other bonds. (1) Intramolecular disulfide bond, (2) free sulfhydryl group, (3) intermolecular disulfide bond, (4) ionic bond, (5) van der Waals bond, (6) interpeptide hydrogen bond, (7) side chain hydrogen bond. Source From A.H. Bloksma, Rheology of Wheat Flour Dough, J. Texture Studies, Vol. 3, pp. 3-17,1972.

The reducing capacities of sulfite should be emphasized as well. In fact, cleavage of S-S bonds by sulfite can be considered a reduction. This property of sulfite makes it useful as an additive to flour for biscuit making (Wedzicha, 1995). The cleavage of disulfide bonds in wheat proteins speeds up and facilitates the production of a satisfactory dough. 

Several models for the structure of wheat glutenin have been proposed. One of the earliest molecular models was that of Ewart [62]. He subsequently modified the model. Ewart s latest model shows one disulfide bond between two adjacent polypeptide chains of glutenins, which consist of linear polymers. Ewart pointed out that the rheological properties of dough are dependent on the presence of theologically active disulfide bonds and thiol groups as well as on secondary forces in the concatenations [63]. 

Wheat cultivars differ in the content of their thiol and disulfide groups (Table 15.40). This implies that the stabUity of a dough may be strongly influenced by a SH/SS exchange between a low molecular weight SH-peptide and gluten proteins. This also implies that a positive correlation... 

Refined soft wheat flours treated with chlorine. Chlorination breaks disulfide bonds, weakens the gluten, lowers pH, and bleaches the flour. Hours usually contain from 7.5% to 10% protein and, upon hydration and mixing, yield weaker gluten doughs compared to regular soft flours. 

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