Effect Of Tea Extracts On The Bread Quality And Polyphenols Antioxidant Activity

Tea extract is extracted from tea materials, it contains some special functional compositions, such as tea polyphenols, tea polysaccharide, and the main component is catechins. Recently studies found that tea extract possess the features of antioxidant, hypoglycemic, lipid-lowering, anti-cancer, anti-bacterial and prevention of cardiovascular disease as well as other activities. Bread is one of the most popular staple food in the world. In view of the convenient and nutritive value of bread, which has become the basis of all civilizations’ diets. In this paper, the tea extract was added in bread staple food system, to study the effects of different amounts of tea extract on dough rheological properties, gluten and dough microstructure. Using those basic datas of macroscopic and microscopic research to explore the effects of tea extract on the dough processing quality, it would provide a useful guideline of relationship between polyphenols and gluten by meanings of analyzing the texture, sensory properties on the quality of bread, and then evaluating bread antioxidant property. Holistic study the effects of tea extract on the dough and bread quality. This research provided the instruction for preventing degenerated disease with the method of daily diet.The main research and results are as follows:(1) The dough development time, stability time, stretching resistance, distance, storage modulus(G’), loss modulus(G’’) and loss tangent(tan δ= G"/G’) of wheat gluten with different amount of tea extract addition at different frozen storage time were studied by using farinograph, texture analyzer and a rotational rheometer. The results showed that adding 1.5 ‰ tea extract in dough, development time and stability time were prolonged, stretching resistance and distance were increased, G’、G’’ of the dough was increased and tan δ was reduced. These results suggested that adding 1.5 ‰ tea extract enhanced dough gluten network structure and increased internal polymer content of the dough, which improved the processing properties of dough.(2) Microstructure and group changes of dough were analyzed by SEM、Tecan Sunrise. The results showed that with the increase of tea extract content, the content of sulfydryl increased and free amino groups decreased, EC/EGC- gluten protein interaction results further verified the non-covalent forces such as hydrogen bond is formed between the tea extract and the gluten. By SEM observation, the structure of starch- gluten become pyknomorphic after adding 1.5 ‰ tea extract. Gluten network connected with each other tightly and formed a fibrous gluten network structure.(3) Through the evaluation of bread quality, the study found that tea extract had no significant effect on the yeasts activity and specific volumes of bread. The analysis of structure characteristics suggested that 1.5‰ tea extract improved the quality of bread. In this condition, the bread had exquisite taste and flexible structure. Furthermore, compared with the control group, the bread which was added tea extract expressed better good water retention. Using Fuzzy mathmatics evaluation method to evaluate the sensory properties of bread, the study found that adding 1.0 ‰ and 1.5 ‰ tea extract bread score were higher than other three groups, which showed that this bread have satisfactory consumer acceptability, which has a certain guide significance in tea extract practical application.(4) By Measuring the total phenolic content, this study found tea extract had a high retention rate in bread. The retention rates of bread crust and crumb polyphenols substance were 95.67% and 92.00% respectively. In the crust, ABTS+, DPPH+ and ? OH radical-scavenging activity were increased by 26.68%, 69.85% and 33.62%, while, in the bread crumb, the three values were increased by 29.06%, 61.18% and 42.69%, which indicated that the tea extract bread had a strong antioxidant capacity. When the bread was storaged three days at room temperature, bread crust and crumb polyphenols substance loss rate reached 95.67% and 92.00% respectively. Indicating that with the extension of storage time, the bread polyphenols would lose activity, which meant that we had to eat bread within three days to prevent losing its nutritional properties.