Studies On Effects Of Oxidized Starch On Dough Properties And Bread Qualities

In this paper, different oxidation degrees of oxidized starches were prepared, and their physicochemical properties were determined. Then oxidized starches were added to wheat flour, and the influences on dough rheological properties, gluten formation, and bread baking characteristics were studied. Besides, the effects of oxidized starches on the changes of bread properties during six-days storying time were studied. The following results were achieved.1. Six oxidation degrees of oxidized starches were prepared, the carboxyl content of the oxidized starches were0.07%,0.13%,0.27%,0.34%,0.40%,0.62%, respectively. The results of physicochemical properties showed that there was no significant change on the starch particle size distribution after oxidation. The paste transmittance and sedimentation were increased with carboxyl content, while the water separation rate was decreased. And after oxidation, the starches initial gelatinization temperature were reduced, paste viscosity were significantly reduced by the increasing of oxidation degree. Finally, the oxidation reaction improved the paste stability, decreased retrogradation values and weakened the gelation property. 2. When added5%oxidized starches, the influences on wheat dough rheological properties showed:oxidized starch which carboxyl content was0.27%could extend dough stability time to7.4min and reduce the soften degree to75FU. Oxidized starch within carboxyl content in the range of0.40%to0.62%made the dough farinograph characteristics deteriorated. Oxidized starch could improve the dough extenograph properties, the resistance force and extensibility of dough reached their maximum when added oxidized starch within carboxyl content of0.40%and0.34%, compared to the blank, they increased respectively35.70%and9.93%. The hardness, springiness and adhesiveness of the wheat dough were improved and the oxidized starches within0.34%carboxyl content showed the best, the hardness, springiness and adhesiveness of the dough with it could increased13.07%,2.78%,14.29%than control.3. Oxidized starch could reduce the content of free hydrosulfide group in gluten protein. When added5%oxidized starches, compared to the control, oxidized starches within0.27%and0.34%carboxyl showed the best. Free hydrosulfide group in unfermented and fermented dough were maximum reduced by19.87%and29.09%. Under the same condition, the result of SDS-PAGE electrophoresis showed this two degree oxidized starches made the gluten protein oxidized most significantly, the color of glutenin electrophoretic bands were deeper than other samples. The gluten quality was enhanced when added oxidized starches, and transmittance and swelling volume in gluten-lactate solution reached maximum of89.15%and22.95mL when added oxidized starches within0.34%and0.40%carboxyl content. Observed the dough microstructure, gluten film could package the starch granules better, and improved the organizational structure of the dough when oxidized starches.4. The influences of oxidized starches on bread baking characteristics showed:the bread specific volume with5%oxidized starch within0.34%carboxyl content was increased by8.7%compared with the control, but smaller than bread specific volume with glucose oxidase(13.6%). And the organizational structure of crumb was improved, and compared to sample within glucose oxidase, there was no significant difference. Besides, oxidized starch increased the whiteness of crumb, reduced hardness, increased springiness and cohesiveness, these improvements were better than glucose oxidase sample.5. During the storage, the increasing rates of bread hardness, gumminess, chewiness and the decreasing rate of springiness became slowly when added oxidized starches. After6days’storage, the aw values of bread with oxidized starch were reduced much slowly than glucose oxidase and control breads. Oxidized starch as a hydrophilic substance, would be better to lock the moisture and reduce it escape to the air.Summarizing the above conclusions, oxidized starch within0.34%carboxyl could be used as the component of bread improver, and the effects in respects of bread texture and color were superior to glucose oxidase.