2021 年 38 巻 p. 40-43
To confirm the effect of black tea on manganese intake, the extraction of manganese from black tea leaves to the tea infusion was examined. Thirty-one tea leaf samples (black tea, 22; flavored black tea, 5; Chinese Puar tea, 1; Louis Bosti, 2; herbal tea, 1) were collected. An infusion was prepared by adding 160 mL of boiling water to each 3 g of leaf sample and allowing it to stand for 3 minutes. The manganese concentration of tea leaves was measured by fluorescent X-ray analysis, and that in tea infusion was measured using an atomic absorption spectrophotometer. The manganese concentration of 28 samples using leaves of Camellia sinensis was 684 (257 to 2259) µg/g, which was significantly higher than that of 84 (58 to 131) µg/g for Louis Bosti or herbal tea without leaves of Camellia sinensis. The manganese concentration in the infusion of 28 samples was 1.64 (0.34 to 6.74) µg/mL, and a significant correlation (R2 = 0.75) was observed with the concentration in tea leaves. The manganese extraction rate of 28 samples into the infusion was 12.4 ± 4.8 %. Comparing the extraction rates for each shape of black tea leaves, the values of the tea leaves that were cut and crushed by a machine and then shaped into a round shape were significantly higher than those of needle-shaped elongated large leaves or finely cut leaves. Since it is calculated that nearly 1 mg of manganese can be ingested by drinking 3 teacups of black tea infusion, habitual drinking of black tea is a factor that significantly increases manganese intake.