Cereal Chem 40:314 - 322.  |  VIEW ARTICLE

Determination of Sulfhydryl and Disulfide Groups in Flour and Their Relation to Wheat Quality.

C. C. Tsen and J. A. Anderson. Copyright 1963 by the American Association of Cereal Chemists, Inc. 

A study has been made on the conditions for determining sulfhydryl (-SH) and disulfide (S-S) groups in flour using a rapid-dropping mercury electrode as indicator electrode and ethyl mercuric chloride as titrant. A flour sample of 0.2 g., or less, is dispersed in 8M area by means of continuous magnetic stirring in nitrogen. The sulfitolysis is carried out at 37 C. and pH 9.0 [NH(4)Cl-NH(4)OH] for 5 min. The amperometric titration is done at -0.75 v vs. Ag/AgCl reference electrode. The method gives accurate and reproducible results. For a sample of Thatcher flour, the mean value of S-S groups, based on nine determinations, is 16.12 plus or minus 0.06 microeq./g. -SH and S-S contents of representative varieties for three types of wheat flour have been determined by this method. The hard wheat flour contains the highest number of S-S bonds; the soft wheat flour, the least S-S bonds and -SH groups. On the protein basis, the soft wheat flour contains the highest and the hard wheat flour the lowest number of S-S bonds. The durum wheat flour, on the other hand, contains more -SH groups than the others. These findings provide an interesting clue to the "quality" differences among proteins in the three types of wheat flour.