About "Essence and Influencing Factors of Tea Color and Fragrance". Professor Cheng gave a systematic introduction from the following four aspects:

1. The Essence of Tea Color

Tea color includes three aspects: dry tea color, soup color and tea dregs color. The color of tea varies greatly depending on the type, age and production process of tea.

The dry tea color of green tea is mainly formed by chlorophyll, lutein, carotene and tea polyphenols with different degrees of oxidation. The dry tea color of black tea is generally dark black to brown, this color is the oxidation product of chlorophyll, pectin, protein, sugar and tea polyphenols in black tea attached to the surface of the leaf, and it appears after drying.

The color of tea soup varies greatly depending on the type of tea. The color of black tea is red, and the color of green tea is green-yellow. This is determined by the characteristics of the respective tea making process. Although the substance that forms the soup color is very complicated, in essence, it is mainly caused by the types of tea polyphenols and their different degrees of enzymatic oxidation and automatic oxidation. Although other plant pigments are affected, they are of secondary importance and have little effect.

2. The Essence of Tea Aroma

There are various types of tea aroma, so-called "clear fragrance", "fresh refreshing", "floral fragrance", "fruity fragrance", "sweet fragrance", "grassy fragrance", etc. are all people's sense of smell and taste organs, a comprehensive response to various aroma substances. In essence, all types of aromas have a material basis.

The aroma of tea is not determined by one or two substances but is often composed of dozens or even hundreds of aromatic substances mixed in a certain proportion. When some substances occupy a place, they show a certain aroma. For example, floral fragrance: phentlethanal, geraniol, nerol, citronellol, geranyl acetate ester (rose), orange blossom acetate (rose), jasmone (jasmine), benzene methyl acetate (jasmine), phenyl propanol (daffodil), linalool, etc.

The aroma of oolong tea is mainly caused by the withered leaves in the process of repeated shaking. Terpene alcohols such as neroli terpene alcohol, the main component of the oolong tea aroma, are often present in the form of glycosides in fresh leaves. After shaking, under the action of glucosidase, the terpene alcohol glycosides are decomposed, so that the terpene alcohol becomes a free state, thereby exuding a rich floral fragrance.

3. The Essence of Tea Taste

The taste of tea is very different due to the type and quality of tea. Taste is the comprehensive reaction of people's taste organs to the taste components in tea. The taste components in tea are relatively complex, as many as dozens, and changes in their types, contents and proportions have a profound impact on the taste of tea soup. The pungent astringent substances in tea soup are mainly tea polyphenols (mainly catechins), the bitter substances are mainly caffeine, anthocyanins and tea saponins; the umami substances are mainly amino acids and the sweet substances are mainly soluble sugar and some amino acids, sour substances are mainly organic acids and some amino acids; fresh substances are mainly complexes of amino acids, catechins, theaflavins, and caffeine.

The ratio of tea polyphenols to amino acids is 2~3 : 1 in Angie White Tea, and 6~9 : 1. When the ratio is high, the bitterness is heavy, the mouthfeel is rough.

4. Factors of the Color and Aroma

Many factors affect the color and aroma of tea, such as latitude, altitude, season, light, temperature, moisture, soil, cultivation technology, variety, tea tenderness, processing technology, storage conditions, etc.

The obvious difference in quality between spring tea and summer tea is mainly due to changes in the metabolism of tea trees caused by different temperatures. The relatively low temperature of spring tea is beneficial to the formation and accumulation of nitrogen compounds. Therefore, the total nitrogen content and amino acid content are higher, but for carbon metabolism, the temperature is lower and the metabolic intensity is lower, so the content of sugar and tea polyphenols converted from sugar is higher than that of summer with high temperature. Tea is correspondingly lower. The amino acid content of spring tea is much higher than that of summer tea. The amino acid content of late spring tea is higher than that of early summer tea. This is the main reason for the high quality of spring tea and the low quality of summer tea.

The original content is shared by Professor Cheng Qikun, Honorary Vice President of China International Tea Culture Research Association. Translated by Bonna Tea.