The taste of Tieguanyin with light fermentation and heavy fermentation has always been a hot topic of online discussion. Some people prefer lightly fermented Tieguanyin, while others prefer heavily fermented one, which can be said to be a matter of personal preference. In fact, the degree of fermentation of Tieguanyin is determined by many factors, including market factors and raw material factors. If we delve into its biochemical essence, we may have a more adequate understanding of the differences in the degree of fermentation.
One, Shape:
The difference in the appearance of Tieguanyin is mainly caused by physical differences. Modern processes are highly mechanized, with greater mechanical strength in shaping, resulting in granular dried tea.
Traditional process: higher humidity during wrapping and rolling, advocating hot rolling, higher capillary water content in cellulose, better toughness, higher pectin content, better adhesion, easy to wrap and shape.
Modern process: drying, low-temperature wrapping and rolling, just opposite to the traditional process, tea is easy to break, less pectin exudes, poor viscosity, difficult to shape, can only rely on mechanical repeated wrapping and rolling.
Two, Color:
Richly fragrant Tieguanyin: Due to varying degrees of oxidation of polyphenols and other substances in the leaf heart, edges, and stems during the Qing-making process, it exhibits a clear phenomenon of green stems, green belly, and red edges. Chlorophyll, through enzymatic or non-enzymatic pathways during the Qing-making, killing-green, prolonged wrapping and roasting processes, most has decomposed into de-magnesium chlorophyll esters, then combines with other pigments to form lustrous dry tea color. Water-soluble flavonoids partially oxidize, causing the tea soup to appear orange-yellow or brown-red.
Freshly fragrant Tieguanyin: The above color substances have undergone less oxidation and transformation, with less damage to chlorophyll. Due to less de-magnesium chlorophyll ester formation from low-temperature re-firing, it achieves the modern Tieguanyin's "three greens (green leaves, green soup, green bottom)."
Three, Aroma:
The aroma of Tieguanyin is mainly composed of alcohols, esters, aldehydes, ketones, and other aromatic substances. They partly come from fresh leaves, partly result from enzymatic reactions during the Qing-making period, and partly are formed by physicochemical reactions induced by thermal effects during baking and re-firing processes.
Richly fragrant Tieguanyin: Moderate enzymatic oxidation of polyphenols, along with the degradation of some amino acids and fatty acids within the leaf tissue, forms traditional Tieguanyin aromas dominated by components such as geraniol, indole, and ionone. Among these, geraniol and indole are particularly prominent.
Freshly fragrant Tieguanyin: The oxidation of polyphenols and the transformation of other aromatic substances are not as complete. However, during the long cooling Qing-making process, aromatic substances undergo slow transformation, followed by high-temperature killing-green, allowing low-volatility substances like grassy-smelling cis-3-hexenol to volatilize. Partial degradation and transformation of amino acids and fatty acids form the unique fresh and sharp aroma of Tieguanyin made with new techniques.
Four, Taste:
The taste of Tieguanyin is a coordinated complex of multiple flavors. The main contributors include the sweetness of soluble sugars, the astringency of tea polyphenols and their oxidation products, the freshness of amino acids, and the bitterness of caffeine. Various taste-contributing substances interact antagonistically and synergistically.
Richly fragrant Tieguanyin: During the Qing-making process, with partial evaporation of water and damage to leaf cells, internal substances undergo a series of oxidation and hydrolysis reactions. The content of bitter and astringent tea polyphenols decreases, while the content of sweet-tasting soluble sugars and soluble pectins increases. The content of fresh and sweet amino acids such as theanine and glutamic acid also increases, and the content of bitter caffeine slightly decreases, thus forming a rich, fresh traditional tea flavor.
Freshly fragrant Tieguanyin: There are also a series of changes and transformations in the traditional process during Qing-making, but the extent and direction of these changes and transformations are not entirely consistent. The main difference lies in the lighter oxidation of polyphenols under the new process, resulting in fewer oxidation products such as theaflavins, thearubigins, and theabrownins, making the tea soup less concentrated. However, due to protein conversion producing amino acids and less degradation and transformation of amino acids, the tea appears clearer, purer, and fresher.