Understanding Semi-Oxidized Tea: A Guide to its Features, Types, and Process

Tea is a popular beverage that has been enjoyed for centuries. It comes in various types and flavors, each with unique features that make it special. One way to classify tea is according to its fermentation or oxidation degree, which gives rise to four categories: unoxidized tea, semi-oxidized tea, oxidized tea, and fermented tea. In this article, we’ll explore semi-oxidized tea, which is often the least talked about.

What is Semi-Oxidized Tea?

Semi-oxidized tea, as the name suggests, is tea that has been oxidized halfway. Oolong tea is one of the most well-known examples of semi-oxidized tea. It sits in the middle ground between black tea (fully oxidized) and green tea (unoxidized). In Japan, oolong tea used to be the only semi-oxidized tea, but in recent times, some farms have started producing an unusual semi-oxidized Hōjicha (roasted green tea) that has become a hot topic. In China, the birthplace of tea, semi-oxidized tea is further classified into three types based on the degree of oxidation.

Features of Semi-Oxidized Tea’s Flavor, Aroma, and Color

Semi-oxidized tea has a pleasant aroma that is more aromatic than green tea. It is slightly bitter but has a deep, savory flavor. The refreshing tea is often preferred after a heavy meal with a strong taste, such as meat and Chinese food. The oxidation process yields aromatic components that make aromas and pigment components that make colors. Catechin is a component that influences the color of tea. As oxidation turns the liquid color (the color of brewed tea) redder, black tea, an oxidized tea, has a red liquid color. In the case of semi-oxidized tea (oolong tea), which is oxidized only halfway, the liquid color stays brownish, halfway between green and red.

Features of Semi-Oxidized Tea’s Ingredients

Tea leaves contain various ingredients. The process of oxidation yields aromatic components to make aromas and pigment components to make colors. Catechin is a component that influences the color of tea. As oxidation turns the liquid color (the color of brewed tea) redder, black tea, an oxidized tea, has a red liquid color. In the case of semi-oxidized tea (oolong tea), which is oxidized only half, the liquid color stays brownish, halfway from green to red.

Features of Semi-Oxidized Tea Process

The manufacturing process of semi-oxidized tea starts with sun-drying fresh leaves. They are then spread and roasted for some time in a room. The roasted tea leaves are put in a cloth bag for a while. After kneading and drying, the tea is ready. While oxidized tea is placed in a humid room to be fully oxidized, semi-oxidized tea undergoes roasting to halt oxidization.

Types of Semi-Oxidized Tea

In Japan, semi-oxidized tea is rare, but in China, it is further classified into three types based on the degree of oxidation:

White Tea (Bai Cha)

White tea is the least oxidized semi-oxidized tea and is also known as “weakly oxidized tea.” Its manufacturing process does not include kneading.

Blue Tea (Qing Cha/Oolong Tea)

Oolong tea is a type of blue tea. Its degree of oxidation varies widely by type, but blue tea is the most common semi-fermented tea.

Yellow Tea (Huang Cha)

Yellow tea has undergone a special heating treatment. After ripening the half-oxidized leaves, the liquid color becomes yellow, as its name suggests.