Abstract:

The stability of tea polyphenols in aqueous solution as a function of concentration and temperature was
investigated with respect to the changes in color difference, transmittance, absorbance, pH values, zeta potential and
catechins contents. The results showed that the stability of tea polyphenols greatly varied with different concentrations
and temperatures. During the sterilization and storage, aqueous solution of tea polyphenols exhibited a gradual decrease
in lightness and transmittance, a darkened color appearance and consequently an increase in absorbance at 425 nm,
and a considerable reduction in catechins contents and pH. These changes were more marked at higher concentrations.
Significantly higher changes in color different, transmittance, absorbance, pH and catechins contents were observed when
stored at 25 ℃ than at 4 ℃. The zeta potential was negatively related to the concentration of tea polyphenols, suggesting that
these compounds were more stable at lower concentrations. Based on the above results, we conclude that tea polyphenols in
aqueous solution at concentrations between 400 and 800 mg/L are relatively stable when stored at 4 ℃.

Key words: tea polyphenols, stability, concentration, temperature