Cereal Chem 42:86 - 96.  |  VIEW ARTICLE

The Improving Mechanism of Ascorbic Acid.

C. C. Tsen. Copyright 1965 by the American Association of Cereal Chemists, Inc. 

The improving action of ascorbic acid (AA) is due to the oxidation of -SH groups in dough by dehydroascorbic acid (DHA), an oxidation product of AA, as shown in this study. When flour [is] treated with DHA, isoascorbic acid (IAA), or AA and mixed in nitrogen, only DHA-treated doughs show a significant decrease in -SH content. The -SH oxidation is closely associated with the improving effect of DHA on dough, proving that DHA has the typical action of a flour improver. DHA does not react with -SH groups in dough as fast as iodate or azodicarbonamide, but it reacts faster than bromate. The IAA-treated doughs, whether mixed in nitrogen, air, or oxygen, do not show any significant differences in -SH content from the controls. The inactivity of IAA reveals the specificity of the enzymatic system. AA is effective for the -SH oxidation in the presence of oxygen, indicating that AA should be oxidized to DHA first to exert its improving action. For a mixing process where the oxygen supply is limited, the use of bromate or air can accelerate the action of AA by oxidizing AA chemically rather than enzymatically. In addition, bromate can supplement DHA to oxidize -SH groups in dough to enhance the improving effect.