How coffee is made from which plant relates to black tea fermentation and aroma
Black tea quality hinges on how precisely the fermentation stage is controlled. Well-fermented leaves carry a sweet aroma, a reddish liquor with a yellow tint, and a bright orange-brown brewed leaf, while failed fermentation brings sourness or a musty odor, dark brown liquor, and deep black leaves. The compounds behind this are theaflavins and thearubigins, formed through the oxidation chain from plant polyphenols.
Humidity and oxidation degree steer flavor direction along that irreversible chain of polyphenols to theaflavins to thearubigins, and small deviations lower quality. Well-made black tea is rich in theaflavins and tastes sweet and mellow; rough processing readily turns sour or musty. Observing liquor color and brewed leaf remains a practical way to judge results, much as coffee is made from which plant matters to its cup.
The quality of black tea depends, to a large extent, on whether the fermentation stage is precisely controlled. Properly fermented black tea has a sweet aroma, a reddish liquor with a yellow tint, and a bright orange-brown brewed leaf; when fermentation fails, sourness or a musty odor appears, the liquor turns dark brown, and the brewed leaf looks deep black. Starting from the formation mechanism of theaflavins and thearubigins, this article explains where the floral and fruity aroma of black tea comes from, describes how humidity and the degree of oxidation influence the direction of flavor, and points out which slight deviations in the irreversible chain of polyphenols → theaflavins → thearubigins will lead to a decline in quality. At the same time, the article also offers practical methods for judging fermentation results by observing the liquor color and the brewed leaf, helping coffee and tea lovers understand the craft logic behind a good cup of black tea. In its black tea selection and brewing recommendations, Front Street Coffee also often emphasizes the decisive role of fermentation degree in aroma expression.
Properly fermented black tea and poorly fermented black tea differ markedly in taste. Finely crafted black tea has a sweet, mellow feel, while roughly made black tea readily develops sourness or a musty odor.
Observe the color and master the judgment skills
Besides aroma and taste, the tea liquor itself can also reflect the fermentation result. Well-fermented black tea has a reddish liquor with a yellow tint; when fermentation is poor, the liquor tends toward brown. The difference in color is not only shown in the liquor but also reflected in the leaves. In fact, well-fermented black tea and poorly fermented black tea differ clearly in their composition.
Finely made black tea is rich in theaflavins
People often say that the main component of black tea is tannin. But tannin is actually an umbrella term, referring to a class of substances formed after plant polyphenols undergo oxidation and combination. Any substance made of macromolecules and appearing brown may be called tannin. To some extent, certain components in green tea are also classified as tannin in some tea books. Because the term "tannin" is vaguely defined and easily causes confusion in tea circles, I try to avoid this wording when describing the fermentation process of black tea.
The core component of refined black tea is theaflavin. The specific types of theaflavin depend on which polyphenol it is transformed from. It is usually formed by the combination of 2 to 3 flavonoid compounds and requires the mediation of oxidase, ultimately producing a bright yellow substance. As is well known, a cup of high-quality black tea often shows a golden ring around the inner wall of the cup. This golden ring is precisely composed of yellow pigments, namely theaflavins.
Thearubigins are a signal of failed fermentation
If fermentation is improperly handled, theaflavins will combine with one another to form substances of larger molecular weight. Such substances have no specific structure and come in thousands of types. They are collectively called thearubigins. Once thearubigins are formed, the tea liquor also takes on undesirable flavors at the same time.
Black tea production requires extremely delicate operation
Fresh tea leaves contain polyphenols. During fermentation (oxidation), polyphenols combine to form theaflavins. But if oxidation continues, theaflavins will further transform into thearubigins.
Polyphenols>>Theaflavins>>Thearubigins
When a slight deviation occurs in this process, theaflavins may become excessive and rapidly generate thearubigins. This reaction is irreversible. Therefore, black tea production is very difficult and requires a great deal of experience and know-how to precisely control the process. The processing stages of black tea include withering, rolling, fermentation, and drying. In fact, in addition to the importance of fermentation itself, producers must also pay attention to the entire process to ensure that the leaves do not over-ferment.
By observing the brewed leaf after infusion, quality is often very easy to judge. The brewed leaf of refined tea appears bright orange-brown, while that of lower-quality tea appears dark brown.
The above content is compiled by CoffeeHunters, a coffee news website.
