How Much Caffeine is in Taiwan Oolong Tea
How much caffeine is in Oolong Tea or tea leaves in general isn't as cut and dry as many articles out there would have you believe. The majority of articles simply state how many milligrams of caffeine are in a cup of tea and ignore important factors like brewing temperature, ratio of water to leaves, brewing method, and the specific type of tea. Here, we look at the factors that affect how much caffeine there is Oolong Teas with a look at Taiwan Oolong Teas in particular.
Pure caffeine is a bitter and white crystalline solid at room temperature
Caffeine is a crystalline, white, bitter compound that is very soluble in hot water, and is one of the most influential substances determining the flavor of tea. Caffeine in plants helps deter pests and can keep competing plant seeds from germinating nearby. In dried tea leaves, caffeine can account for 2-5% of the leaf by weight. How much caffeine goes on to a cup of brewed tea depends on several factors.
The temperature of the brewing water is one of the biggest factors in determining the caffeine content of a cup of tea. Taiwan’s Tea Research and Extension Station (TRES) measured the caffeine content of a number of Taiwan teas after brewing at different temperatures. The teas were brewed using 3g of tea in 150ml water, using temperatures of 80°C, 90°C, and 100°C (boiling) water for 5-6 minutes. Only the first steeping of each was used to measure caffeine. The teas examined were as follows and the results plotted in Graph 1.
- Bilochun Green Tea, spring harvest, Qing Xin Gan Zai strain.
- Wenshan Baozhong Tea, fall harvest, Qing Xin Oolong strain.
- High Mountain Tea, fall harvest, Qing Xin Oolong strain.
- Dong Ding Oolong Tea, fall harvest, Qing Xin Oolong strain.
- Oriental Beauty Tea, summer harvest, Qing Xin Da Mao strain.
- Black Tea, fall harvest, Tai Cha #8 strain.
Graph 1. Caffeine Content vs. Steeping Temperature for Various Teas
Source: Taiwan Tea Research and Extension Station
As Graph 1 clearly shows, boiling water brew drew out the most caffeine for all types of teas. Incredibly, the caffeine released with boiling water was about double that of 80°C water for all tea types. Based on this information, an 8oz (240ml) cup of tea prepared with boiling water gives us the following figures.
Amount of caffeine in a cup of a variety of teas
Number of Steeps
TRES also examined the effect the number of steepings had on caffeine content. Graph 2 shows the caffeine content of different steepings of Green Tea (three grams of Green Tea brewed in 150ml of water) under different temperatures and times. The third steeping of the hot brew had only 30% of the caffeine content of the first brew, and the 4th brew (not shown) only had 9%.
Graph 2. Green Tee Caffeine Content vs. Brewing Method
Source: Taiwan Tea Research and Extension Station
Cold Brew for the Least Caffeine
Furthermore, Graph 2 shows that Green Tea brewed at 4°C for intervals of two and four hours, undergoing repeated brews for a second and third interval, showed a much lower caffeine content that the hot water brewings. This goes to show just how much caffeine is easily dissolved in hot water. So people who are sensitive to caffeine, but still enjoy drinking tea, may want to use the cold brew method, or opt to drink only the second or third steeping of tea in hot water.
Cultivar and Growing Conditions
The caffeine content in tea leaves is also influenced by the cultivar, the position of the leaf on the tree, the growing season, climate, and overall growing conditions of the tea trees. Different cultivars of tea leaves can vary significantly in their caffeine content, and young leaves have higher concentrations than mature ones.
The cultivar of the tea and the growing conditions affect caffeine content
Summer and fall growing seasons produce higher levels of caffeine content in the new leaves than spring and winter due to the more extensive growth during these seasons. More shaded leaves have relatively higher caffeine levels.
Caffeine crystals on a tea roasting oven
The heat of roasting tea leaves sublimates the caffeine, meaning it turns it directly into a gaseous form, releasing it into the air. This is evidenced by the crystallized caffeine that forms on the surfaces of the ovens and walls and ceilings of tea roasting rooms. Because of this, roasted teas, in general, will have less caffeine that unroasted teas. So if you’re looking for a robust flavor profile with less caffeine, explore the vast array of roasted Oolong Teas.
Tea aging in urns
Aging tea leaves results in mellowing their flavor profile, and brings forth a deep, rich, sweet character that is reminiscent of both preserved fruit and smoked food products. And while the science behind this effect is yet to be full researched, it stands to reason that the bitter flavor of tea that is mostly due to caffeine content is slowly being transformed into different chemical compounds that offer a milder, sweeter flavor profile. So again, if you are looking for full bodied, rich, complex flavors in tea, but don’t want the caffeine boost, Aged Tea is a good choice. And in this respect, the more mellow and smooth the flavor profile is, the more likely there is less caffeine content in the brewed tea!
So, as you can see, there are many factors that go into determining how much caffeine is in a particular cup of tea. Here’s a summary:
- Brewing tea at lower water temperatures releases less caffeine than boiling water.
- Repeated steepings having increasingly less caffeine content.
- Different cultivars and growing conditions have various influences on the caffeine content in tea.
- Summer and fall harvests have higher caffeine content than spring and winter harvests.
- Unroasted teas generally have higher caffeine content than roasted teas.
- Aging tea presumably reduces the caffeine content in tea by slowly breaking down the caffeine.
If you enjoyed reading this post, check out our piece on how Taiwanese Oolong Tea is made in which we delve into the details of what makes Oolong Tea special.
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