Cereal Chem 38:438 - 448.  |  VIEW ARTICLE

Accessible Sulfhydryl Groups in Dough.

W. Bushuk. Copyright 1961 by the American Association of Cereal Chemists, Inc. 

The rapid reaction of iodate ions with sulfhydryl groups was applied to the determination of the accessibility of these groups in flour-water doughs. The maximum amount of iodate that reacts in a dough was obtained graphically, from amperometric titrations of residual iodate, by plotting residual iodate vs. iodate added and extrapolating to zero residual iodate. Reasonable agreement with calculated values for the number of sulfhydryl groups was obtained for doughs which contained added glutathione or thiolated gelatin, and no reaction with iodate was obtained when sulfhydryl groups were blocked with N- ethylmaleimide. Increases in accessible sulfhydryl groups were obtained for doughs prepared from flours of decreasing particle size, doughs subjected to prolonged mixing, and doughs treated with guanidine hydrochloride to break hydrogen bonds. These results indicate that iodate ions react primarily with accessible sulfhydryl groups. Illustrative results for doughs from eight different flours ranged from 4.0 to 7.5 microequivalents per g. of protein. Within a single class of flour, the number of accessible sulfhydryl groups increased with increasing protein content. The method was also used to determine the number of accessible sulfhydryl groups in flour-water slurries for one sample of flour.