A: (1) color. Tea in the storage process, due to the role of oxygen and light in the air, so that the composition of the tea color of some pigment substances undergo slow automatic decomposition. Such as green tea in the chlorophyll decomposition results, so that the color from the new tea when the verdant green gradually become yellow-green withered gray. The oxidation of ascorbic acid (vitamin C), which is more abundant in green tea, produces pheomelanin, which makes the tea soup become yellowish-brown and unclear. The oxidation, decomposition and polymerization of fucoxanthin, which has a greater impact on the quality of black tea, as well as the result of the auto-oxidation of tea polyphenols, will make the black tea become grayish-brown from the darkness of the new tea.

(2) Taste. When shopping for tea, be sure to taste it yourself. The best tea can only be realized in the process of tasting and comparing. Stale tea due to the oxidation of esters in the tea produced a volatile aldehydes, or insoluble condensate, the result is that the soluble in water to reduce the active ingredient, so that the taste from mellow to become thin; at the same time, but also due to the oxidation of amino acids in the tea, so that the tea taste of freshness weakened and become dull.

(3) smell aroma. Stale tea due to the oxidation of aroma substances, condensation and slow volatilization, so that the tea from the fragrance becomes low turbidity. Scientific analysis shows that there are more than 300 kinds of components that constitute the aroma of tea, mainly alcohols, esters, aldehydes and other qualities. They are in the tea storage process, both volatile and slow oxidation. Therefore, with the prolongation of time, the aroma of tea leaves will become lighter, the aroma will become cloudy and low by the new tea when the fragrance fragrance.