The Effect Of Tannic Acid On Gluten Protein Structure, Dough Property And Bread Quality

In China, common wheat (Triticum aestivum L.) is one of the most important staple food crops and the cheapest source of calories and protein for local inhabitants. And China is the one of the most important wheat growing and consuming countries in the world. However, before the 1980s, flour milled from Chinese wheat had lower dough strength and poorer end-use quality even at a similar protein level to wheat from some other countries. China imports large amounts of wheat grain from western countries in order to meet the requirement for various foods such as bread, dumpling, noodles, steambread and cake.So the new, safty and efficient additives are needed to investigated.The effects of tannic acid, which is present in many plants, on the structure of gluten protein and the properties of dough and bread were studied.This thesis has two parts of research. First is about the impact of tannic acid on the rheological properties and breadmaking quality. And tannic acid gave a really good influence on the rheological properties. Second is about the effects of tannic acid on the gluten protein structure. Tannic acid is really different from other redox agents of gluten protein. The reduction agents can also act positive influence on gluten proteinTannic acid was added at 0.1%,0.2% and 0.3% respectively during dough making process. The tannic acid acted negatively on disulphide bond formation and can interact with gluten proteins by other covalent bonds as detected by UV-spectroscopy and dynamic rheometry. The rheological properties and texture of the bread were measured by a Farinograph, Extensograph and texture profile analyzer, respectively. Texture analysis indicated little change in adhesiveness and resilience of bread at three levels of tannic acid compared with the control, but the changes of hardness and chewiness of bread made with addition of tannic acid, indicated that tannic acid could delay the bread staling process. The effect of tannic acid on flour and dough is different from other flour redox agents. It broken down the disulphide bonds but also acted positive effects on dough property and bread quality. Disulphide bonds are always commonly considered as the most important factor to change the quality of bread. But this paper presents a new concept of some other covalent bonds can also improve the quality of flour and bread, and use this property to investigate the new, safety and efficient additives of flour.