If you put a pinch of tea leaves in 1 cup of water, do you get the same amount of caffeine as you would if you put it in 2 cups of water, or ½ the caffeine, or something in between? Assume a standard steeping time.
If you let the tea steep even longer does that have an effect on the answer or does virtually all the caffeine come out in the first go?
Caffeine is one of the quickest things to be dissolved in the tea leaf, so you can effectively decaffeinate at home by pouring a cup and then immediately replacing the water. There will still be some caffeine left, of course, but only a small portion of it.
The amount of caffeine present in the entire brew has to do with the amount of tea leaves, not the amount of water. So 2 cups will have the same caffeine as 1 cup when using the same number of leaves.
Now, I suppose it’s possible to reach some sort of caffeine saturation point where only by adding more water will you be able to increase the caffeine. But a pinch in 1 cup won’t come anywhere close to that level. That would probably happen when the water is so low, the leaves basically become one solid mass. But at that point, the problem becomes that you’re not effectively brewing your tea, caffeine be damned.
That raises the quesion – what IS the saturation point? If Chronos’s post is accurqte, the opposite has got to be accurate, too – you can get a hyper-caffeinated beverage by dunking several tea bags in hot water for several second apiece, then adding one final bag in for flavor.
A kind of silly nit pick, but the driving force for mass transfer is concentration gradient. What this means is that mass transfer occurs until the concentration is the same in all areas. So by doubling the water, you half the concentration in both the water and the tea leaves. Practically this means you will get a gnats fart more (mass) in the water. IE for 1 cup and 1 tsp (whatever those are) you might get a 50mg/L solution, you are throwing away 50mg/L in the tea leaves. For 2 cup and 1 tsp, you might get 25mg/L solution, but you are only throwing away 25mg/L in the tea leaves.
Somewhat more practically, this is why we use counter current decantation in leaching. My prof liked to use a coffee example for counter current decantation. Take fresh coffee grounds, and make coffee. There will be a lot of caffeine in the water, but there will still be some in the grounds, and we want that caffeine because that is how we make our money. So we can make coffee again using the spent grounds and fresh water, this will get a little more caffeine out. Now we have a normal strength solution of caffeine and a dilute strength. We don’t want this, we want one concentrated solution of coffee. What if we used the dilute strength on the fresh coffee grounds? The solution used to make caffeine with fresh grounds will always be at the highest possible concentration because it is in equilibrium with the highest concentration coffee; we want this because it makes the rest of the mill cheaper (less volume). The number of times you brew the coffee depends on practical considerations, but with about four to six stages you can get everything out.
Good answer.
Of course, caffeine isn’t the only psychoactive element in tea. There’s also theanine, theophylline and theobromine, all of which have some stimulating effects. Any idea how quickly they extract in water?
This is what “naturally decaffeinated” processes use.
Sorry, that’s not true. It is, however a common misconception.
Another message board I’ve been to referred to this article from this article debunking the idea that caffeine can basically be “rinsed out” of tea:
Here is a link to the actual study (abstract only, full text PDF purchasable). The article also mentions other studies that more or less confirm this data. (There is a lot of variability in how long it takes to tea to infuse, but nothing comes close to indicating that you can eliminate out most of the caffiene in just a short rinse.)
I wanted to say that Alan was wrong but I’ve done some research and he is right. The “caffeine affinity” explanation holds no water.
Thanks for the reference. I do note that this common misconception (I accept your reference) is repeated in Harold McGee’s “On Food and Cooking” [Scribner, 2004, p. 440]. So it is a popular idea.
I bought a package of Chinese tea once-- which had been packed in China-- and the directions said to pour hot water over it, dump that out, and then pour in more hot water to actually make the tea. I never found out why you’re supposed to rinse off Chinese tea leaves first. Maybe they have dust on them? Or it’s supposed to make a smoother flavor? Or is it to make a low-caffeine brew?
It’s definitely not for the caffeine. The main reason AFAICT is simply that everyone’s always done it that way. The main justifications seem to be cleanliness and flavor.
The cleanliness makes a certain amount of sense. Tea is an agricultural product that isn’t always processed in perfectly hygenic conditions. You wouldn’t eat fruit or veg without rinsing off the dirt and bug poop or cook bried beans or rice without looking for stones or other detritus, so why would you drink tea that way?
OTOH, neither the quick rinse most people give their fruit and veg nor the brief steep the Chinese give their teas is likely to actually remove much of anything. But at least it gives peace of mind. I’ve found some strange things in tea before (though I like pu erh tea, which is basically tea that’s been kept in a compost pile for a few months - no way I’ll drink that without rinsing it!).
The flavor argument is that the leaves are typically tightly rolled or twisted, and the rinse gives them a chance to open up and make the next infusion more flavorful. This is true (especially for green tea, oolongs, and pu erh), but I don’t know why you couldn’t just infuse for 30 seconds longer rather than pour out the water after thirty seconds. (ETA–or however long you rinse for. Times vary from as briefly as possible up to 30 seconds or more depending on the type of tea and personal habit.)
Note, however, that the Chinese typically brew in a small pot using a lot of leaves and then steep them several times. If you’re going to brew five or six cups of tea in succession, and the first cup is the least tasty, why not just throw it out? You’re still going to get your money’s worth from the tea.
Couple points:
If you remove the tea bag and then double the amount of water, the amount of caffeine will be halved. However, if you drink all of it, you will get the same amount of caffeine either way, which, if you wanted to reduce the amount of caffeine, the obvious answer would be to drink half as much of the original amount of tea.
There should be a point where a particular amount of water just can’t dilute any more of a substance. (Remember those elementary school science projects about growing sugar crystals?)
That’s true, but caffeine is very soluble, so that you can dissolve 2.17 grams per 100 mL of water at 25°. For comparison, a cup of coffee has something like 100 mg per 200 mL. A cup of cold saturated caffeine solution would give you the caffeine of 40 cups of coffee or 20 no-doz (!). At higher temperatures solubility is even higher, 67 g / 100 mL at 100° (!!!). So saturation isn’t preventing the caffeine from entering solution. I’m guessing that it’s just locked up fairly tightly in the tea leaves, even though it is ridiculously soluble. (though as Alan Smithee mentions it doesn’t dissolve as quickly as I thought. Ignorance fought!)