Why Does Tea Need to be Fermented? What Changes Occur During Fermentation?

Tea fermentation refers to the oxidation of catechins, which results in the majority of the color and flavor, as well as the breakdown of related compounds into aromatic components. The primary purpose of tea fermentation is to improve the taste of the tea and to develop and enrich its aroma. So why does tea need to be fermented? And what changes occur during fermentation?

Why does tea need to be fermented?

Since fermentation is primarily for improving taste, the more polyphenols that give us a bitter taste are oxidized, the smoother the taste of tea will be. The rule is that the heavier the fermentation, the less bitter taste the tea will have; conversely, the bitter taste will be more pronounced.

• Green tea is unfermented

When we drink green tea, we are actually drinking the genuine taste of tea. Isn't the most prominent feeling of tea the bitter taste, especially for summer and autumn tea? If all teas were processed like green tea, it would not be good for those who do not like the bitter taste or have stomach problems to have a relationship with tea. However, the production of fermented tea was not originally created with a clear purpose. In fact, almost all fermented teas are directly or indirectly derived from failed green tea processing. In modern times, scientists have standardized them one by one according to different processing methods, fermentation levels, and quality characteristics, thus forming various tea categories.

• Yellow tea is slightly fermented

Under high humidity and high-temperature conditions, polyphenolic compounds undergo non-enzymatic automatic oxidation, producing yellow tea polyphenols - that is, a small amount of oxidized substances are produced by reducing polyphenols, which form the unique golden color and slightly mellow taste of yellow tea, compared to green tea.

• Oolong tea is semi-fermented

Its fermentation is mainly completed during the green-making process. Green-making causes enzymatic oxidation of polyphenolic compounds, generating more tea polyphenols, which form the rich floral aroma, strong taste of the inner substance, and the red edge of the green leaves. Compared with green tea, both the aroma and taste of tea have been significantly improved.

• Black tea belongs to fully fermented tea 

In theory, its full fermentation is completed during the entire process of withering, rolling, and redness, that is, its polyphenolic compounds are 100% oxidized by enzymatic and heat reactions, generating mainly theaflavins, with a small amount of tea polyphenols, making the tea soup mellow, sweet, not bitter, and the aroma is also sweet and rich. However, in production, fermentation cannot actually reach 100%, so there is usually a slight astringency, which is normal.

Tea fermentation is a process that has been used for centuries to produce a variety of flavorful and aromatic teas. But why does tea need to be fermented, and what changes occur during the fermentation process?

First of all, tea fermentation is primarily used to improve the taste and aroma of the tea. During fermentation, polyphenols in the tea leaves are oxidized, which results in a change in color, flavor, and aroma. The longer the fermentation process, the more the polyphenols are oxidized, and the darker the tea becomes. Green tea is an example of an unfermented tea. Because it is not fermented, the tea retains its natural flavor and aroma.

On the other hand, black tea is a fully fermented tea, which results in a rich, full-bodied flavor and aroma. Oolong tea is a semi-fermented tea, which means that it is partially oxidized. During the fermentation process, the polyphenols in the tea leaves are enzymatically oxidized, resulting in a floral aroma and a rich taste. The leaves of oolong tea are also partially green and partially brown, which gives the tea its unique appearance. During the fermentation process, the chemical composition of the tea leaves changes. The polyphenols are oxidized and broken down into new compounds, which are responsible for the color, flavor, and aroma of the tea. These new compounds also have health benefits, such as antioxidants and anti-inflammatory properties.

Tea fermentation is an important process that affects the taste, aroma, and health benefits of the tea. Whether it's green, black, or oolong tea, fermentation plays a crucial role in the development of these distinct tea varieties.

HSF Biotech in terms of enhancing the natural flavor of tea through microbial decomposition, recombination, and reduction, flavor targets can be set, personalized fermentation process control plans can be formulated based on the targets, and the path to achieving them can be established. Each step of the fermentation process can be finely quantified, and a series of key points can be accurately targeted for control and adjustment.