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[2Bp-06] Changes in color and composition of green tea due to light irradiation
Keywords:green tea, chlorophyll, color, light, catechins
【Purpose】 Green tea beverages in PET bottles are known to discolor after long-term storage. One of the causes of this discoloration is known to be light fading of chlorophyll, a green pigment in green tea. We have previously shown that a low-concentration alcohol-water solution or emulsifier can suppress the light fading of chlorophyll1-2). However, the detailed mechanism of green tea discoloration. Therefore, the purpose of this study was to investigate the effects of light irradiation on the color of green tea and its components such as catechins.
【Methods】 Chlorophyll was dissolved using sucrose fatty acid esters (SE) as an emulsifier. Ethanol and the surfactant Triton X-100 (TX) were used as a comparison. The sample solutions were irradiated with LED lights, and color difference, UV-Vis and fluorescence spectra were measured. The same experiment was also conducted with a green tea solution using matcha. The analysis of catechins and other components was performed by HPLC.
【Results】 Chlorophyll in ethanol and TX solutions turned from green to brown when exposed to light, while the green color was retained in SE. The Soret and Q bands of chlorophyll decreased with light irradiation, but the peak at 540 nm increased, suggesting that this peak is responsible for the color change. On the other hand, in green tea solution, light-induced discoloration could not be suppressed even with SE, and catechins also decreased. From the above, it was inferred that the light-induced discoloration of green tea was due to the decomposition of chlorophyll and the formation of components by the interaction between chlorophyll and catechins.
Yasuda M., et al. Food Chem., 277, 463-470 (2019)
Yasuda M., et al. J. Food Chem., 86, 3033-3045 (2021)
【Methods】 Chlorophyll was dissolved using sucrose fatty acid esters (SE) as an emulsifier. Ethanol and the surfactant Triton X-100 (TX) were used as a comparison. The sample solutions were irradiated with LED lights, and color difference, UV-Vis and fluorescence spectra were measured. The same experiment was also conducted with a green tea solution using matcha. The analysis of catechins and other components was performed by HPLC.
【Results】 Chlorophyll in ethanol and TX solutions turned from green to brown when exposed to light, while the green color was retained in SE. The Soret and Q bands of chlorophyll decreased with light irradiation, but the peak at 540 nm increased, suggesting that this peak is responsible for the color change. On the other hand, in green tea solution, light-induced discoloration could not be suppressed even with SE, and catechins also decreased. From the above, it was inferred that the light-induced discoloration of green tea was due to the decomposition of chlorophyll and the formation of components by the interaction between chlorophyll and catechins.
Yasuda M., et al. Food Chem., 277, 463-470 (2019)
Yasuda M., et al. J. Food Chem., 86, 3033-3045 (2021)