Studies on the After-Ripening of Black Tea

Abstract

The changes of chemical constituents and qualities of black tea during storage were studied. Two kinds of black tea were prepared, namely one was fermented for 45 minutes, the another for 90 minutes. And these teas were stored in a factory room or in a refrigerator (3°-5°C) for one year. The following results were obtained after storage. The changes of the water content, the colour and pH of liquor were tested on every three months. The water content under room temperature varied more widely than under cooling. Though the colour of liquor was lighter under cool temperature than under room temperature, it grew more deeper with the storage.On the pH of liquor a distinct influence was not observed by the storage.The changes of tannin, total nitrogen, and soluble nitrogen content were tested on every six months, but all these substances did not show apparent tendency with the storage conditions.Further, the black tea under one-year storage was tested in detail. The infusion was dialyzed through a cellophane membrane in distilled water. And the presence of saccharides and nitrogen in the non-dialyzed portion was tested, for considering whether melanoid pigment was made or not during the storage. As a result, saccharides did not present, but nitrogen a little. Polymerized tannins were contained in the following order : i. e. 90 minutes fermentation-room temperature storage, 45 minutes room temp., 90 minutes-cooling and 45 minutes cooling.The gallic acid content was arranged in the same order.By the paper chromatography of phenolic substances developed with phenol containing 25% water a narrow fraction on the original line was observed, and it was presumed to be polymerized tannins.On the flavor, colour, and strength of liquor by sensory testing, all items under the room temperature storage were superior to those of under cooling storage.