Effect Of Tea Polyphenol On The Slow Digesting Properties Of Starch And The Mechanism

The research is on the influence and mechanism of tea polyphenol on postprandial glycemic response in the presence of starch with different structures, the results may provide a significant way to make use of starches and may be beneficial to prevention of diabetes using appropriate carbohydrates with tea catechins.The main research contents are as follows:A suitable way to detect glucose in the presence of tea catechin was chosen through comparison of results measured by the tradition methods with the actual content of glucose in the system. The Hexokinase (HK) method is proved to be the proper way to detect glucose in the presence of tea catechin compared with the DNS and GOPOD method. In the in vivo experiment, Kunming mice were fed with different starches in which tea polyphenols had been added, and the concentration of postprandial blood glucose was measured. The results using starch with different structures showed different effects on the postprandial glycemic response in the presence of tea polyphenols. Specifically, the glycemic response was decreased when normal corn and waxy corn starch were used with tea polyphenol while high amylose starch produced a higher glycemic response in the presence of tea catechins. Furthermore, Mice were fed with high amylose maize starch in which tea polyphenol had been added at different time and in different doses. The effect of tea polyphenol on the second meal of mice was also detected. Gelatinized high amylase starches in the presence of tea catechin at different time and in various doses showed some slowly digestible effect, the best of which is high amylose starch with 5 %/5 % tea catechin before and after gelatinization respectively. All of the starches and starches-tea catechin system have no effect on the second meal of mice.The inhibition kinetics of tea polyphenol on the in vitro digestion of starch was studied. The maximal inhibition rate is 50 % as the concentration of TPLs reached 12.5 %. And the inhibition rates are depended on the content of tea catechin.Besides, tea catechin was added in starches to observe the effect on the retrogradation of starched with different structures. The DSC and XRD were carried out to detect possible interactions between starch and tea catechins. The tea catechin postponed the retrogradation of starches with different degrees depending on the content of tea catechin, structure of starch and retrogradation time. The DSC results indicate that the tea catechin can reduce the retrogradation enthalpy while the XRD analysis showed a decrease of crystallinity. At the same time the addition of tea polyphenol can cause the congregate of starch molecule. The laser differaction analyzer were used to detect the chages on particle diameter of starches after the addition of tea polyphenol, and it proved to increase the particle diameter of starch. The starch and tea catechins composite with the best slowly digested effect obtained in the study was also used to study its effect on the aging process of mice induced by injection of D-galatcose. The results showed the protection effect of slowly digested starch on the aging of mice.In a word, Tea polyphenol may be combined with the starches to affect the postprandial glycemia response of starches with different structures. The high amylose starch-tea catechin system can be manipulated to have a slowly digestible effect, which might protect the aging process of mice caused by the D-galactose.