Abstract
The effects of L-ascorbic acid (L-AsA) and sodium D-isoascorbate (D-AsA-Na) as an improver for breadmaking on the physical properties of wheat dough and starch were studied with use of a domestic breadmaking apparatus. D-isoascorbic acid (D-AsA) was oxidized to its dehydro-form in a yield of 50% by AsA oxidase in a neutral buffer solution, while L-AsA was about 90%. After addition of D-AsA or L-AsA (100 ppm) to the ingredients for breadmaking, D-AsA remaining in the dough during the mixing for 30 min was about 10%, while that of L-AsA was only 4%. Addition of 20 ppm D-AsA-Na to the ingredients for breadmaking increased the specific volume of the bread, while lower and higher concentrations gave a decrease. The addition of 50 ppm D-AsA-Na to the wheat flour increased the mechanical stability of dough during mixing as compared to that of the control or D-AsA, by farinography. Also, addition of D-AsA-Na in the dough showed filamentous and viscous states intermediate between those of L-AsA and control, respectively, as evaluated by scanning electron microscopy. Furthermore, the gelatinization temperature of starch in the dough containing D-AsA-Na (50 ppm) after mixing for 25 min decreased to about Sit which is intermediate between that of L-AsA and control. The results suggested that D-AsA-Naoxidized the SH groups of gluten mildly, followed by SS-cross linkage which changed the wrapping of the starch granules, thereby causing a decrease in the gelatinization temperature.
