Taste of tea

The oxidation products such as theaflvins and therubigins contribute to tea color and taste of the black tea. Moreover, tea quality is also determined by the processing techniques employed. The three basic types of tea; green, oolong and black have different quality characteristics, including aroma, taste and color, and appearance.

Compounds which contribute to characteristic tea taste are poly‐phenolic compounds, amino acids, caffeine, etc. Very complicated mixtures of volatile compounds, such as terpenoids, alcohols, carbonyl compounds, etc., contribute to characteristic tea aromas.

Taste of food is mainly composed of five basic sensations; that is, sweetness, astringency, sourness, bitterness and umami . A delicious cup of tea infusion is an ingenious balance of various taste sensations.
*Astringency is a drying, puckering sensation in the mouth that affects the whole of the tongue more or less uniformly. Tannin has a strong astringent or pungent taste. Tea has high tannin content. It congeals proteins on the top of the mucous membrane layer of one’s mouth and makes the tissues contract.
* Bitterness is usually unpleasant, but sometimes desirable in moderate amounts, and is perceived predominantly at the back of, and sometimes along side of, the tongue. Caffeine is the stimulant in green tea. Caffeine possesses a bitter taste, and the detection threshold is 3 ppm in water, which is 0.0003% .It, is important in tea flavor and briskness.
* The umami is a Japanese term, it is similar to the “meaty” taste or “brothy” taste.

Besides catechins and caffeine, some amino acids (such as arginine, alanine, etc) also contribute to the bitterness of green tea infusion. The amino acids in green tea area major factor in its quality, with about 20 different amino acids contributing to the overall content. Theanine accounts for more than 60% of the amino acids; theanine, glutamic acid, asparagines, arginine, and serine account for about 90% of total amino acids. Amino acids are mainly responsible for brothy taste. The umami taste of green tea infusion was shown to be due to some amino acids such as theanine, serine, etc and the sweetness to sugars.

Taste of tea

Taste of tea

Besides the aroma, the taste quality is also one of the key criteria used by tea tasters to describe the quality of tea liquor.

Green tea, oolong tea and black tea all have their own distinctive flavors. Its taste is at first bitter and astringent and then sweet.

The balance of astringency, bitterness and brothy taste is important to the characteristic taste of tea; catechins and caffeine are counted as the major contributors to astringency and bitterness.

The major catechins in green tea are EGCg, ECg, EGC, and EC, which are classified as either gallate-type catechins (EGCg and ECg) or non-gallate type catechins (EGC and EC) by the presence of galloyl group on the oxygen atom at the C3 position.

Human perceive the taste of the gallate-type catechins to be more bitter astringent than that of the non-gallate type catechins.

Black tea and green tea are different in flavor due to the fermentation process during production of black tea, in which catechins are oxidized and polymerized to form theaflavins; and consequently the astringent taste of green tea is replaced with more complex astringent taste.

Theaflavin constituting about 0.3 – 1.8% of black tea dry weight and 1- 6 % of the solid in tea infusion. It contributes significantly to the bright color and brisk taste of tea infusions.

During a few minutes infusion, catechins from tea leaves are not fully extracted. The preparation method will affect the extraction efficacy and consequently the content of polyphenols in the cup.
Taste of tea