Oolong Tea Processing: Roasting/Baking Technology in Production

March 2, 2016 6247 view(s)
Oolong Tea Processing: Roasting/Baking Technology in Production

When it comes to the processing of oolong tea, there are many similar steps overlapping with other types. Still, oolong tea is in itself a very unique category, because of the baking/roasting technology applied. This processing step is important as it significantly affects the final taste, aroma and appearance of oolong tea. That’s why we’re dedicating a whole article to only this step based on the knowledge shared by farmer Qin who has 32 years of experience in the production of Da Hong Pao.

The Purpose/Effects of Roasting Oolong Tea

  • Reduce 
Water Content: Roasting will reduce the water content of oolong tea. Keeping water content between 4-6% can prevent the tea from deterioration in order to prolong storage life.
  • Remove Raw Smell: Another purpose is to remove the raw smell of the tea. By heating and dehydrating, the amino acids and sugars in the tea leaves will turn into chemical components that result in a more pleasant and richer aroma, when the leaves are steeped.
  • Stop Oxidation: At last, this step also stops the oxidation of leaves and allows the tea to be in the best condition for further ripening when stored properly.

Control Factors & Considerations

Water content

The main priority of roasting is to reduce the water content in the tea leaves to a proper range (4-6%) and to slow down oxidation of the leaves. This process will prolong the storage life of the tea.

Tea leaves with different water content have different roasting conditions. There are no high tech measuring tools used. The tea master will judge based on experience how much water content is left in the tea. When the water content of the tea is above 8.8%, mold will appear; when it’s at 12% or above, tea leaves will gradually deteriorate.

Generally, for tea with high water content, the roasting temperature should be 95 ℃ to 100 ℃ and with extended time at the initial stage of the roasting; If the roasting continues for more than 3 hours, the temperature must be lowered to 85 ℃ or so, to let the slow heat bring out the nice and rich aroma of the tea. There are however other factors that the tea master needs to consider, which are discussed further below.

Tea leaves with high water content should be spread out thinly, otherwise the leaves will suffer from improper ventilation and compromise the quality of the tea.

Tenderness of raw tea leaves

Roasting thicker and older tea leaves requires medium temperature (85-90 ℃), roasting time ranges from 4 to 10 hours depending on the demands of different types of tea leaves. For example, roasting time should be shortened for thick and old tea leaves with less fragrance. Tender tea leaves requires higher temperature than the old ones, the roasting starts with medium to high temperature (90-100 ℃) for 4 to 10 hours, then the temperature should be lowered to 80-85 ℃ for 2 to 4 hours. This procedure ensures that the beverage tastes good without bitterness and retains the fragrance and character of the tea leaves.

Shape and tightness

Tea leaves with tight shape are more resistant to heat. The roasting temperature should be lower at 85-90 ℃ with longer hours. As for loosely shaped tea leaves, appropriate roasting temperature should be 100 ℃ and for a short time.

Aromas

The aroma of oolong tea is what makes this category so special. However, it's also the most difficult to control. Slight differences in processing can have a big impact on the aroma. The end result is therefore extremely volatile. Delicate aromas can easily to escape during the roasting process, when the temperature and baking duration isn't well controlled.

See below a list of fire levels and the related scent that the farmer wants to obtain as an end result.

  • Low fire: great to obtain a flowery scent. The resulting tea will steep a light yellow liquor. The leaf appearance after steeping is green with red edges.
  • Medium fire: suitable for leaves that can obtain a fruity scent. The liquor will be gold yellow.
  • High fire: results in a caramel like scent. The liquor will be dark yellow or orange.

Generally, it's suggested to use low temperature and short roasting time for tea leaves with fresh scents and good quality. For tea with less fragrance and lower quality, it is suggested to use high temperature and long roasting time to cover the lack of quality. In the latter case, the tea master will still try to make the best of it. The priorities are to remove the unpleasant scent and to lower the water content. They should be first roasted at high temperatures for a short time, then followed with roasting the next day in this order: 80℃ for 2h → 90℃ for 2h → 100℃.

At last, it's important to note that the level of roasting will depend on the consumer demands. It's generally known that Guangdong tea drinkers like a darker roast than other parts of China (and outside of China).

For lighter oolongs, in order to maintain the green color and strong aroma, the roasting temperature should be low (60 ℃ - 70 ℃) and the duration will be controlled until the water content is from 5% to 6%. Unlike dark oolongs, green oolongs should be vacuum packed in time to avoid aroma loss.

Flavors

If the tea leaves are sweet and mellow in flavor, they should be roasted first at a medium temperature of 80-85 ℃) for 4 to 6 hours, then at 75-80 ℃ for 2 to 3 hours the following day. Avoiding high temperature will prevent the tea from tasting ripe or bitter and maintain the quality of the tea.

Heat control

Heat control dictates the levels of chemical and appearance change to the tea leaves during roasting. It effects the tea leaves in shape, in color before and after brewing, as well as the color of the brew. Appropriate heat control can make up for some deficiencies of the tea quality.

On the other hand, improper control will lower the quality. For some special types of tea, if the heat control is correct, it will bring out the nuances in aroma and flavor. Different types of tea have different levels of heat resistance. Tieguanyin and large leaf oolong are more resistant to the heat; teas with richer aromas like Huangdan, Qilan are less resistant to the heat.

Comments
Leave your comment
Your email address will not be published
What's this? Check "Remember Me" to access your shopping cart on this computer even if you are not signed in.