【作者】 李钊；

【导师】 夏涛； 高丽萍；

【作者基本信息】 安徽农业大学 ， 食品科学， 2010， 硕士

【摘要】 绿茶汤色极易受到光照、温度、湿度和氧气等因素影响而发生劣变,从而对绿茶的品质带来不良影响。绿茶中呈色物质很多,且极性分布不一。本研究试采用系统溶剂分离法对绿茶茶汤中呈色物质进行分离,并研究不同温度贮存条件下,绿茶汤色呈色物质的变化情况;采用脱除茶汤儿茶素和黄酮醇的方法,进一步研究导致绿茶汤色劣变的主要因子;通过添加PVPP和β-CD两种护色的方法,研究绿茶汤色劣变的调控。得出的主要结论如下:1、采用系统溶剂分离法,依次用有机溶剂石油醚、无水乙醚、乙酸乙酯和正丁醇萃取茶汤,色差分析和HPLC分析结果显示,茶汤中呈色物质主要富集在极性较大的正丁醇相和水相中,正丁醇相主要是黄酮醇类的物质,水相物质成分有待进一步确定。2、绿茶茶汤在贮存进程中会发生褐变反应,且随着贮存温度的升高,茶汤颜色的劣变加剧。引起汤色劣变的物质主要分布在正丁醇相和水相。在绿茶汤色劣变过程中,儿茶素类物质含量明显下降,可能发生了降解、氧化、脱没食子化和异构化反应从而影响汤色变化;观察到黄酮醇苷类物质的水解反应,但并没有发现黄酮醇类物质含量的明显上升或下降。3、脱除儿茶素类物质的茶汤,其汤色劣变仍然较为明显,推测可能存在黄酮醇类物质的氧化降解;脱除儿茶素类和黄酮醇类物质的茶汤,其汤色则未发生明显改变,推测茶汤中除了儿茶素和黄酮醇类物质外,其他物质对汤色劣变的影响非常小。4、与正常茶汤相比,加入PVPP后的茶汤,由于PVPP的吸附作用,其酯型儿茶素含量下降;其汤色劣变有所减缓,但黄酮醇苷类物质含量下降较快。与正常茶汤相比,加入β-CD后的茶汤,其汤色劣变也有所减缓,并抑制了儿茶素和黄酮醇类物质的降解。5、去除儿茶素和黄酮实验、添加PVPP实验结果均说明儿茶素的氧化还原电位高于黄酮类物质,当儿茶素被吸附后,黄酮失去了儿茶素的保护而迅速被氧化。更多还原

【Abstract】 Green tea is vulnerable to various influencing factors, such as light, temperature, humidity and oxygen, which will exert negative influence on its quality. There are diversified chromogenic substances with different polarity distribution in green tea. This study aimed to separate chromogenic substances in green tea infusion by Systemic Solvent Segregation, found out the change of these substances under different temperatures. By depriving tea infusion of catechins and flavonols, dominant factors leading to the degradation of tea infusion color were further analyzed, and through adding PVPP andβ-CD, measures of keeping green tea infusion from degrading were studied. Following conclusions were obtained:1. By applying Systemic Solvent Segregation, organic solvents such as petroleum ether, anhydrous ether, acetic ether and n-butyl alcohol were respectively used for green tea infusion extraction. Results of color difference analysis and HPLC analysis showed that chromogenic substances in tea infusion mainly concentrated in N-Butanol phase and aqueous phase with relatively greater polarity, and there were mostly flavonols in N-Butanol while substances in aqueous phase to be further analyzed.2. Green tea infusion turned red and brown in the process of storage, and with the rising temperature, degradation of tea infusion color was aggravated. Substances leading to color degradation were mainly in N-Butanol phase and aqueous phase. In the degradation process, the concentration of catechin substances largely decreased, which might be caused by degradation, oxidation, gallic acid removal, or isomerization, and further led to the change of tea infusion color. Hydrolysis reaction was found among flavonol glycosides, but there was no obvious increase or decrease in the concentration of flavonols.3. After being deprived of catechins, color degradation of tea infusion was still obvious, it was inferred that there might be oxidation of flavonols. Being deprived of catechins and flavonols, color of tea infusion changed slightly which indicated that substances other than catechins and flavonols had only subtle influence on the color degradation of tea infusion. 4. Tea infusion with PVPP had less catechins than normal tea infusion did due to the absorption effect of PVPP, its color degradation rate was also reduced, but flavonols concentration decreased quickly. Tea infusion withβ-CD had slower color degradation, and the degradation of its catechins and flavonols was also restrained.5. The flavonols were oxided quickly after removing catechins because the redox potential of catechins is higher than that of flavonols.更多还原