(1)Observe the color: green tea will turn from emerald green and fresh to yellow and dark, and some teas with higher fermentation, such as black tea, will become as if covered with ash.
(2) Smell the aroma: of course, the changing trends of different teas during storage are different. Under good storage conditions, white tea and black tea are easy to develop pleasant aromas such as jujube, medicine, fragrant wood and so on. However, green tea, white tea, yellow tea, and lightly fermented oolong tea may have a stale taste, and the original aroma may become light and not lasting. Often times, there will be an oily smell in the aged Longjing, and some teas also absorb other odors during storage. After all, "tea is easy to dye", in short this is mostly unpleasant.
(3) Taste the flavor: green tea will lose its original freshness, and black tea may become sou.