Caffeine


Lichee Black TeaA hot cup of tea. That’s the basic, right? You take your tea leaves, you soak them in boiling water until a reasonable amount of caffeine has come out, and you inhale that sucker as soon as it cools enough not to scorch you. Then you stare at the computer screen, decide you still don’t feel awake, and repeat the process. Wait, is that just me?

OK, I don’t do that (always). Being the cultured tea snob that I am, I would of course never put boiling water on a delicate tea leaf. Near boiling, perhaps, for a hearty black, but that’s all. And for your more delicate greens, water down to 160 or even 140 degrees might be wise. And then if you want it iced, which you probably do in the summer heat, you drop ice in until it’s cold. But does the water have to be that hot? As you’ve probably guessed, I wouldn’t have asked the question if the answer was yes.

Heat speeds up and strengthens chemical reactions. So heat in your water makes your tea steep faster, and it lets the water drag some larger molecules out of the leaf, but the action will still happen, even with quite cold water. Here at the tea shop we need things to happen fairly quickly, since people are lining up at the register, so we usually make iced tea by making a normal pot of tea and then applying ice and refrigerators until it’s at proper iced tea temperature, but at home I usually make my iced tea by putting leaf in room temperature water, then putting it in the fridge to steep overnight. This is called cold-brewing. My mother has a middle approach; she puts the leaf and water in a large clear jug out in the sun all afternoon, so the water is warmed up by the sun, and making what is called ‘sun tea’, but doesn’t get up to normal steeping temperatures unless you live in a seriously toasty climate. All three approaches make very tasty and very different cups of tea.

There are two things that change when you change your brewing temperature:

First, is time needed. You exchange water heat for steeping time. So tea brewed with boiling water is done in three minutes, my mom’s sun tea is done in four or five hours, and I pour a glass of my fridge tea after eight to ten hours (although some people will cold brew for as few as four and like it that way. Experiment and see what you like). If you want to try cold-brewed tea, you must plan ahead of time!

Second, the flavor changes. Cold water can’t get the big molecules loose from the tea leaves, so the tea you end up with tastes different. The most distinct change is that cold-brewed tea is less bitter than normally brewed. Less of the caffeine is dissolved in the cold water and caffeine, a strongly bitter chemical, is the primary reason that tea has a bitter flavor. Cold-brewed tea is often comparatively sweet, and sometimes surprisingly floral. If you’re not sure you’ll like that, try the method on small batches of types of tea you haven’t tried it on before. Conversely, an already sweet tea will often make an excellent cold-brew, since it supports and emphasizes the flavor profile that the tea was designed for. This effect is also great for cheap tea, since any overwhelming bitter or sour flavors will be softened, giving you a fairly tasty and undemanding drink. My mother makes her sun tea with whatever bags are cheapest and come in the largest box at the grocery store, and it’s lovely, especially with a bit of fresh mint.

So, you can have your tea without having to turn your stove on in the middle of this summer’s ubiquitous heatwaves! At least, you can by tomorrow. Set it to steep now, and go see a movie in an air-conditioned theater, you’ll have tea when you get back.

Elizabeth, Teahouse Kuan Yin Staff

Nilgiri Black TeaAssam and Darjeeling are the big names in Indian tea; the one for quantity and the other for quality. They aren’t the only places that make tea there, though. The Nilgiri area has a healthy tea industry, and it’s clawing its way up in the world.

Nilgiri is a range of mountains way down in the southern end of India, at about the same latitude as Sri Lanka, which produces Ceylon tea. It mostly produces CTC tea (cut tear curl, that really finely chopped stuff that looks a little like coffee grounds) for blend, and when I drink a cup of pure high grade Nilgiri tea it reminds me of English Breakfast even more strongly than Assams and Keemuns do. You may not know the name Nilgiri, but the flavor will probably be familiar.

Their production system is kind of different. Only a third of Nilgiri tea is produced by huge plantations; most of it is grown on small farms, which then sell their freshly harvested leaves to processors. The processors have no problem putting out a consistent product, though, which in itself has been a bit of a problem for them. The thing is, when the USSR was buying massive amounts of tea in the 70s and 80s, they dominated the Nilgiri industry. Unfortunately, what the Soviets wanted to buy was leaf that looked pretty when the purchaser looked at it, which only has so much to do with the quality of the tea that results. After a few decades of making tea that the Soviets would buy, Nilgiri wasn’t putting out particularly good tea, and when the USSR collapsed, Nilgiri was left hanging.Decaf Organic Nilgiri Green Tea

They’ve retooled and rebuilt (we have the technology! </notentirelyrelevantreference>) by this point, so the Nilgiri tea industry is slowly getting healthier, and they’re producing some worthwhile teas. We have two, one basic black which is in the picture at the top of the article, and one really quite nifty decaffeinated organic green, fig. 2. The word that springs to mind is unexpected, and when we got it there was a lot of handing around a cup of it and saying “what? Decaf Nilgiri green?” It’s quite tasty, so if you’re looking for something that’s decaf and different, you should definitely try out the green, just like, if you’re looking for something quality and familiar, with a nice caffeine kick, you should try the black.

Elizabeth, Teahouse Kuan Yin Staff

We have an interesting new tea at the teahouse, a decaffeinated, organic, green Nilgiri. It’s very hard to find seriously upscale tea that’s decaf; our other decafs are both blends, English Breakfast and Earl Grey. They’re both quite tasty, but they’re blends of teas from all over the tea making world, generic and solid and not really that interesting. Great for first thing in the morning, or while you’re working on something else, but what if you want interesting tea that you can think about a bit but don’t want any caffeine? Hard to find, until we tracked down this nice Nilgiri. It’s also organic, like our other decafs, so there’s no need to worry about creepy chemical residues (check my article on decaffeination if you want to know more about that). And aside from the whole to-caffeinate-or-not-to-caffeinate issue, it’s special because it’s a green Indian tea. India got into the tea cultivation business to make black teas to ship to Britain, and to this day makes very little green, so this is a really uncommon tea. Surprisingly enough, it’s tasty, too. We try a lot of samples of weird tea that turn out to just be weird and not good, but this one is as tasty as it is interesting. Well worth a try.

Elizabeth, Teahouse Kuan Yin Staff

Up for more technical discussion of the chemical composition of tea? Of course you are! You aren’t going to find out how they get the caffeine out of tea leaves without vocabulary that I, at least, thought I had escaped when I fled my high school chemistry class. The story has a happy ending, though, at least for people who get their decaf tea from our tea shop, so you can read on with the same confidence that you go to a mainstream scary movie with, the pretty heroine will make it out alive, and without even drinking something called dichloromethane.

How Tea is Decaffeinated

Here’s the basic outline for how things are decaffeinated: first, the leaves are soaked in a little water if it’s been dried, so that the chemicals can move around properly. The point of drying them out in the first place is to stop chemical reactions from happening until you combine them with hot water to get them to react into a nice cup of tea, so this has to be undone first. Second, the leaves are exposed to a solvent that dissolves out the caffeine, hopefully leaving the rest of the chemicals in the leaves mostly alone. Then they re-dry the leaves, and voila! The decaf version.

Wait, solvents? Do I want to drink those?

That second step is dodgy, though. First, there is a selection of solvents. Once the solvent touches the leaves it never all comes off, so this is important to you, the decaf drinker, because you’re drinking your solvent, too. One, the dichloromethane from the first paragraph, also called methylene chloride, is such an effective solvent that it’s also used in paint stripper, degreaser, and dry cleaning solution. As you can imagine, it isn’t the safest thing ever ingested, and the US isn’t wild about letting producers put it in our tea. It’s still used in some countries, though, so there is a chance it could end up on your cheap decaf.

A second solvent, ethyl acetate, is found naturally in tea leaves, and so is often called “natural decaffeination.” There’s a lot more ethyl acetate left on a decaf tea leaf than there would naturally be, and it is derived artificially so they can have enough of it to be useful in industrial processes, so it isn’t really that natural. The third solvent is carbon dioxide, put under enough pressure that it’s almost a liquid. While carbon dioxide is bad for the atmosphere, it’s fine for people, so it’s the solvent you want.

Is the tea still healthy like all the articles say it is?

The other problem with the solvent step is that it’s hard to take out just the caffeine and not anything else. Ethylene acetate takes out a lot of the flavonoids, those anti-cancer chemicals, at least a third and usually more like 70%. There are some processes that can be used to filter the caffeine out of the stuff the solvent takes out and then the producers can try to get the rest of the chemicals to dry back onto the tea leaves, but they don’t work that well for tea. Luckily, carbon dioxide is much better about leaving the other chemicals alone, stripping away only about 5% of the flavonoids.

Here’s how that works: Caffeine molecules are smaller than most of the other molecules that make up a tea leaf, so they’re easier for a solvent to move, and since the carbon dioxide is a gas under a carefully calculated amount of pressure rather than a liquid, it can be calibrated to be just dense enough to be able to carry off the caffeine and not enough to take the bigger molecules. Decaffeination with carbon dioxide is technically called “supercritical fluid extraction,” because the carbon dioxide under pressure is called a supercritical fluid, ie a gas put under so much pressure it passes a critical point and starts to behave kind of like a liquid, doing things like dissolving caffeine. Does anyone else want to burst into “She Blinded Me with Science“?

That was a lot of words, and most of them were really long. What should I actually drink?

So carbon dioxide is definitely your best bet, right? Not poisonous, doesn’t take out all the really healthy chemicals, involves awesome and unlikely states of matter. But how can you tell? No one would put any of these words on packaging. There’s a code, though: in the US, and probably most other countries with strict health laws, you shouldn’t run into methylene chloride. As I said above, naturally decaffeinated usually means they used ethyl acetate, and since it’s cheap, it’s generally the default approach. And finally, if your tea is organic, the only way it can be decaffeinated is with carbon dioxide. So! For maximum healthyness of decaf tea, buy it organic. Makes sense anyway, right? All the decaf tea at Teahouse Kuan Yin is certified organic, and we never even thought about it until this afternoon. I love happy endings!

Elizabeth, Teahouse Kuan Yin Staff

Assam HalmariThe mythology about caffeine in tea rivals the Greek pantheon. A lot of people have gone into chemistry labs with a supply of tea to attempt to figure out what’s going on in these leaves and they’ve come out with a lot of information, and everyone siezes their favorite piece and flings themselves into the argument with zeal. After careful research, I have determined that most of the information floating around out there is actually perfectly consistent, it just sounds like it isn’t when you’re having a good time arguing. So! I’m going to write down how it seems to line up to me, and see if it makes any more sense written down together like that.

How much caffeine is in tea?

The basic answer to “how much caffeine is in tea?” is that black tea has half the caffeine of coffee, and oolong has less than black, green less than that, and white less than that. This seems logical, and you drink a cup of black tea and you do feel less stimulated than after a cup of coffee and more than after a cup of green tea, so either it’s right or the placebo effect is in full force. Except there are a lot of people who insist that all types of tea have the same amount of caffeine, and some people will tell you that there’s less caffeine in coffee than in tea, and there’s more caffeine in tea buds than in full grown leaves so white tea ought to have the most caffeine, right? Right!?!Ti Kuan Yin

Leaves and Water

First, it’s important to be precise here. There is more caffeine in tea leaves than in coffee grounds, but there’s more caffeine in a cup of coffee than in a cup of tea. More coffee grounds are used for each cup of coffee than tea leaves for each cup of tea, and because coffee is more finely ground, more of the caffeine is extracted in the brewing process. Roughly the same problem plagues us when we ask how much caffeine is in each kind of tea. Not only are black teas more likely to be cut up into small pieces than other kinds, but they’re also brewed with hotter water. That means more caffeine in your drink! The hotter the water is, the more caffeine is in the final drink. So tea buds can have all the caffeine they like, but unless someone pours boiling water all over defenseless delicate white tea leaves, the final white tea drink is not going to have as much caffeine as black tea does. So if you want tea with less caffeine in it, brew it with cooler water.

What’s in a leaf?

Long Jing (Dragonwell)Another imporant thing to remember is that absolute amounts are not as relevant as percentages. I know, that’s not a very informative sentence, but bear with me, I’ll explain. When a tea leaf is picked, it has a certain amount of caffeine molecules in it, and those molecules are pretty much going to sit around playing poker and chatting until you plunge the leaves into hot water. I mean they aren’t going anywhere, not breaking down or anything. But during oxidation other parts of the tea leaf break down and condense until that caffeine makes up a much larger part of the resulting black tea leaf. So it’s not so much that green tea has less caffeine, it’s that it has more other compounds. I think. I’m going to admit that I’m not entirely sure of this stuff, because I can’t find a study that addresses this exact question, so this is just what I conjecture from what information I can find. Anyone else out there know more about this?

Other factors

Now, there are a lot of other things that have some effect on caffeine content, including, but not limited to: particle size (how finely the leaves are cut up), varietal (assamica has more than the basic variety), position on the plant (buds and new leaves have more than old leaves), the soil the plant grew in, the altitude, whether the plant was grown from a cutting or a seedling, how the plant was fertilized, and what time of year the leaf was picked. These have smaller effects, though, so unless you feel moved to hire private investigators and send them over to Asia with detailed spreadsheets to fill out, it isn’t worth your time to worry about them.Silver Needle

In the end, the black>oolong>green>white hierarchy does hold up. Water temperature is a major reason for this, and I’m pretty sure there’s something going on with the chemical composition of the leaf, but I need my own lab to make sure, and I’ve got a small teahouse and a laptop. Brew your teas at the recommended temperature, and you’re set.

Elizabeth, Teahouse Kuan Yin staff

A few links with more detailed information:

Oxidation and Fermentation in Tea Manufacture is an excellent explanation of oxidation.

Caffeine and Tea focuses primarily on debunking the myth that a brief initial steeping gets rid of most of the caffeine, but it’s full of data that’s both carefully collected and can tell you a lot of different things about caffeine and tea.

The Wikipedia article on caffeine and the Britannica one both help you understand caffeine enough that the explanations of what it does in tea make more sense.