Cereal Chem 40:1 - 9.  |  VIEW ARTICLE

Modification of Flour Proteins by Dough Mixing: Effects of Sulfhydryl-Blocking and Oxidizing Agents.

D. K. Mecham, E. G. Cole, and H. A. Sokol. Copyright 1963 by the American Association of Cereal Chemists, Inc. 

Part of the protein in wheat flour cannot be extracted with 0.01N acetic acid, but is converted to an extractable form by dough mixing. Both the rate and extent of this conversion are increased by adding the sulfhydrylblocking reagent, N-ethylmaleimide (NEMI), to doughs. Doughs from six flours (5 HRW, 1 HRS) were mixed in a farinograph in air and freeze-dried. In the absence of NEMI, maximum conversion of protein required about 20 minutes of mixing, or longer. With additions of NEMI equivalent to the sulfhydryl contents of the flours, maximum conversion was reached in 5 to 10 minutes. In the absence of NEMI, maximum extractable N ranged from 76 to 94% of total flour N; with NEMI added, maximums ranged from 90 to 96%. Potassium iodate produced smaller change than NEMI. Rapid modification of protein solubility properties by NEMI (and potassium iodate) begins as soon as dough mixing starts, although changes in farinograph mixing curves are large only after doughs have reached maximum resistance to mixing. With one of the flours, dough mixing in the absence of NEMI produced little change in the amount of N extractable by 5% sodium chloride, water, or 60% ethanol. In the presence of NEMI, the amounts extractable with 60% ethanol increased with dough mixing as with 0.01N acetic acid, but with water they decreased slightly.