Recently, I was at a friend’s wedding when I started talking about tea (no big surprise). I said something along the lines of “white teas and green teas have more caffeine”, which my seatmate disagreed with heartily. A quick google search proved me wrong, but I was really confused as to why I had that idea in my head, so I embarked on a mini-search to find out where caffeine in tea comes from.

As it turns out, the caffeine content in tea is affected by many things such as:

1. The variety of tea

According to Astill, Conrad, et al. (2011) fresh leaves from the Assam tea leaves (camellia sinensis var. assamica) contain more caffeine than fresh leaves from the Chinese version (camellia sinensis var. sinensis) – 4.01% caffeine compared to 3.11%.

2. The way it’s processed

Also according to Astill, Conrad, et al. (2011), the making of green tea results in more caffeine than black tea. This was a surprise because my seatmate claimed that the processing was the reason for higher caffeine in levels for black tea. But while the caffeine content does rise during withering, it falls when the tea is fermentation and withering stages. This makes sense to me, since puer is lower in caffeine and it undergoes post-fermentation.

I also learnt that black tea made using CTC (which is what you’ll find in most tea bags) has more caffeine than black tea made using the orthodox method.

3. The leaves used

What I learnt (and what made me think that white – and for some reason, green – teas had more caffeine), is that the buds and young leaves of the tea bush has more caffeine. This is because caffeine is a natural insecticide, so that plants sends more caffeine to the buds to protect them. And since white tea is pretty much made of buds, it should have quite a high proportion of caffeine. The findinds of Lin, Yung-Sheng, et al. (2003), which notes that “The level of caffeine in all old leaves (fifth to seventh leaves) was less than that in young leaves (apical bud and the two youngest leaves)“

There’s also less caffeine in the stems of the leaves, which means that teas like kukicha, which are made from the stems, have less caffeine.

4. Location (maybe?)

I couldn’t find a source for this, but what I’ve been told by quite a few people is that the location of the tea makes a difference. High mountain teas are said to be higher in caffeine because of the harsher environment, making growth slow but resulting in a more flavourful (and caffeinated) cup of tea. I suppose this is like the concept of gyokuro and matcha, where the tea bush is shaded before plucking. Not coincidentally, these two teas are the green teas with the highest caffeine.

Overall, it seems like there are a lot of things that affect the caffeine level in a tea. It depends on what variety the tea is, how it was processed, which part of the plant it was from, and maybe even where it’s grown.

Addendum
This didn’t make it into the main post but while I was reading through the different studies, one by Zuo, Yuegang, Hao Chen, and Yiwei Deng (2002) caught my eye. They compared the levels of catechins, caffeine, and gallic acids in different Chinese teas and found that the green teas had the highest level of caffeine (with the Hangzhou Lung Ching coming in first), while the Oolongs had the least amount of caffeine (Fujian Oolong ended up with the lowest levels). Black tea (Fujian black tea), ranked somewhere towards the end, right after Puer (which came as a surprise).

Perhaps I was thinking of Chinese teas when I made my claim?

Sources
Zuo, Yuegang, Hao Chen, and Yiwei Deng. “Simultaneous determination of catechins, caffeine and gallic acids in green, Oolong, black and pu-erh teas using HPLC with a photodiode array detector.” Talanta 57.2 (2002): 307-316.

Astill, Conrad, et al. “Factors affecting the caffeine and polyphenol contents of black and green tea infusions.” Journal of agricultural and food chemistry 49.11 (2001): 5340-5347.

Lin, Yung-Sheng, et al. “Factors affecting the levels of tea polyphenols and caffeine in tea leaves.” Journal of agricultural and food chemistry 51.7 (2003): 1864-1873.

Featured Image: Photo by Me