Studied On The Color Variation Of Green Tea Infusion

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.