Effect Of Tannic Acid On Dough Rheological Property And The Study Of Its Mechanism

From this study to improve the quality of wheat flour point of view, wheat flour with low gluten content was used to explore the action mechanism and effect of tannic acid. Farinograph, Extensograph , scanning electron microscope(SEM) and other analytical tools were used to study the effects of tannic acid on the rheological property and bread quality.In order to investigate the effects of tannic acid on the flour quality, three concentrations of 0.1%, 0.2% and 0.3% of tannic acid were added to the flour. The results of Farinograph date showed that the water absorption, dough stability time and developing time of wheat flour with low gluten content were increased with the increasing added amount of tannic acid. Tannic acid has a good effect to improve the dough rheological property. And the results of Extensograph date of area of the tensile curve, the tensile resistance, the greatest degree of stretch resistance and extension were all increased when tannic acid increased. Tannic acid can also improve the microstructure of dough. And the bread volume is increased too.The activity of flour polyphenol oxidase which negatively related to the bread color were increased because of tannic acid added. The experiment of disulfide bonds and free amino groups content determination showed that the content of disulfide bonds were reduced while the free amino groups decreased with the amount of tannin added increased in dough.Tannic acid's phenolic hydroxyl group combined with gluten and non-gluten protein's free amino groups. And we believed that this new cross-linked formed to enhance the rheological property. Experiments had also proved that this network forming process occurred before the fermentation process. No matter before or after the fermentation, disulfide and free amino group content of the dough was almost unchanged, so the result can prove that this network forming process occurred before the fermentation process.The purpose of this thesis was to propose a new flour redox agent– tannic acid, which put forward a new idea to develop the new flour quality improve agent. It was considered that not only the disulfide bonds but also other covalent bonds can enhance quality of flour.