11

I have a lovely black tea that is fairly high in caffeine, which I'd like to keep.
Unfortunately though, I'm not a fan of the bitterness caused by tannins, and I'd like to remove them if possible without leaching the caffeine as well.
I was thinking pre-rinsing the leaves with cold water for example, considering the solubility figures below:

Tannic acid solubility at 25 degees C: 2850 g/Ll
Caffeine solubility at 25 degrees C: 20 g/l
Caffeine solubility at 100 degrees C: 660 g/l

Are there any experimentally verified methods of doing this?

  • I assume you're set on removing the tannins somehow, rather than masking them or minimizing their taste? – logophobe Mar 17 '16 at 14:28
  • Are you talking about bitterness or astringency ? I cannot imagine a really bitter black tea, however about astringency, I would advice to 1) increase tea quantity 2) lower water temperature 3) shorten infusion time. – TZDZ Mar 17 '16 at 14:33
  • @TZDZ I'd call it bitterness... I can't let tea steep for more than a minute or two without it becoming too bitter to drink without watering down. Some people are more sensitive to this than others (I don't like red wines or hoppy beers, either). – Catija Mar 17 '16 at 23:25
  • 1
    The correct solution to your problem is certainly to find a tea with similar caffeine content, but less bitter taste. There's really an amazing variety of teas; if it's the tannin which bothers you then check out some oolong or green teas. – leftaroundabout Mar 18 '16 at 23:28
  • Caffeine itself is bitter, so you won't be able to remove all the bitterness from tea without also removing all the caffeine. – Ross Ridge Feb 7 at 8:19
10

Adding a 1/4-1/2 teaspoon of gelatin powder dissolved in the boiling water should do the trick. I fermented some arizona and used gelatin to remove the remaining yeast, only to find it removed the tannins as well, yielding a relatively clear liquid with a dark brown sediment at the bottom. I can't guarantee that it won't touch the caffeine, but i see no reason it would chemically.

14
+50

In response to the answer posted by @James, I've run the following experiment:

Ingredients:

  • Black tea by "Tea Merchant", flavor = "Ship Ahoy"
  • Colorless and flavorless gelatin powder, bought from the baking isle in a supermarket.

Process:

1) I made 4 cups of tea, each with 1 tea spoon of tea leaves straight into the cup:

  • Control cup, no addition
  • 1/4 teaspoon of gelatin powder
  • 1/2 teaspoon of gelatin powder
  • full teaspoon of gelatin powder

2) I thoroughly stirred the tea and left the cups to sit for 4 minutes.

3) Poured each cup through a strainer into a fresh receptacle to remove the tea leaves.

4) I left the tea to cool, such that I could take large gulps at a time in order to maximize tannin taste.

Results:

a) The colour was noticeably lighter the more gelatin was added. Below is a photo, where each label indicates amount of gelatin in each cup (as fractions of a teaspoon, where left is full spoon, right is control).

Gelatin contents

b) A large gulp of the control tea was unpleasantly bitter.

c) Each subsequent concentration removed more bitterness, indicating that a relatively large amount of gelatin is required to completely remove all tannins.

d) 1/4 teaspoon was sufficient to remove the unpleasant sharpness

e) The full teaspoon removed most of the tanniny flavor, allowing the more subtle flavors to be tasted.

f) Although I find the full teaspoon left the tea a bit bland as well. I prefer the 1/2 teaspoon ratio.

g) I am slightly disappointed that I did not create tea-jelly. Will just have to add more. For science.

h) I cannot comment on the effect of gelatin on the caffeine levels since I am quite caffeine insensitive.

Conclusion:

Gelatin definitely reduces tannin concentrations which removes the sharpness out of black teas.
I am unable to comment on caffeine levels from "feel", however, this paper models caffeine release from a gelatin matrix. I only gave the paper a quick scan, and I find no mention of gelatin reacting with the caffeine in any way.


EDIT:

Over the course of the weekend I was able to feed a caffeine sensitive friend some tea. Everyone was weirdly suspicious.

Process:

5) I created two 1l batches containing 3 teaspoons of tea leaves, soaked for 10 minutes. The control batch was left untouched and gelatin batch contained 10g of gelatin.

6) Saturday morning at 10 am the subject was given the control tea. He finished it by 10:45, and by 11 am his symptoms were: Elevated heart rate (110 bpm compared to 60 at rest), headache, shakiness and a general feel of ill ease. By 11:30 the symptoms seemed to have passed.

7) Sunday morning at 10 am the subject was given the gelatin tea. To my great pleasure the tea had partially jellified. The subject was not pleased. He finished the tea by 10:45 and reported no symptoms at all, apart from feeling "a bit better". It seems that the subject had somehow ingested some alcohol the previous evening, thereby bringing these results into question.

Results:

f) The gelatin heavy tea didn't really taste that great. The control was expectantly very bitter.

g) We created tea-jelly!

h) Based on the results from subject Friend, gelatin does in fact seem to lower the caffeine levels. Although it may be possible that the jelly caused the caffeine to be released slower (or something). Will have to repeat with much less gelatin, and again with much more gelatin.

i) This would make a really good masters research project.

  • 2
    Do you have access to a lab (e.g. job or university) or lots of money? If so you can do some precision caffeine content analysis. There's a number of methods, if you have access to chloroform, or lead acetate, or benzene and sulfuric acid, or HPLC equipment, or a few hundred dollars to spend. If not, there's also cheap and not too accurate test strips and kits available, which could be a fun test regardless, but their range and precision may not be good enough to tell the difference to you, worth a shot though, may at least give you relative concentrations if the differences are large enough. – Jason C Jan 15 '17 at 14:40
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    @JasonC I was actually just thinking of feeding lots of tea to a caffeine sensitive person until they start shaking. Then repeat a few days later with gelatin added in :) – Roman Jan 15 '17 at 15:28
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    "Drink this. For science." – Jason C Jan 15 '17 at 15:49
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    g) change from gelatin to agar-agar. For science. – Ecnerwal Jan 16 '17 at 0:33
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    @JasonC, See edit :) – Roman Jan 23 '17 at 6:02
7
+25

Usual method of tannin removal is anion exchange chromatography. Linkage:

The primary tannin removal technologies of the past were carbon- and styrene-based ion exchange resin. More recently, acrylic-based and high water retention/low crosslinked styrene-based anion exchange resins have surfaced into the residential water treatment market and seem to outperform the traditional ion exchange resins used for tannin removal. Although no resin is 100 percent effective, success has been greatly increased with these resins. If you haven't tried treating for tannins recently you may want to give it another try.

I have not tryed this with tea, but I have used it on coffee. The result is a clear liquid without much of the bitter taste of cheap coffee. Still tastes like coffee, just better coffee. Not being charged, the caffeine comes straight through, so you still catch a buzz from it. Looks like anion exchange resins are easily available online. You'll probably want food, or at least water system grade. This method will likely work better for some teas than for other. I've no idea what the charge is on the bergamot flavor in Earl Grey, but if it's acidic, it won't make it through the column. Cardamom flavor might make it through. You can either look up the structures of the relevant flavor molecules, and go from there, or just give it a try and see if it works to your satisfaction.

5

I just took an hour finding a solvent that removes tannins and leaves the caffeine behind and yes, it can be done, but no, the remaining tea will be highly toxic.

So unless you're trying to kill your awful in-laws with a de-tanninised black tea high in caffeine, no it cannot be done.

Sorry to be the harbinger of bad news

  • E.G. 200° proof ethanol washes away the tannins too, but also 90% of the caffeine (and probably 100% of the taste). – Fabby Mar 17 '16 at 23:23
  • May I at least know what that solvent is? You know, for science! – Roman Mar 18 '16 at 5:02
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    No need to retrace your steps if you can't remember the solvent. I was just curious. Was just waiting on accepting in case there was a late entry. Thanks for the effort! – Roman Mar 22 '16 at 7:32
  • 1
    I remember it was a complex one: not something simple like Chloroform or Ethanol... – Fabby Mar 22 '16 at 7:41
2

I learned this from a southern friend who took the bitterness out of her tea by adding a pinch of baking soda, so I tried it with every tea I could get store-bought (particularly high-caffeine black tea) and it takes the bitterness right out of it.

Best i can figure the baking soda is neutralizing the tannic acid, though I'm unsure on whether it affects the caffeine content as well.

  • Unsure about the tannins and caffeine, but I read somewhere that it adds electrolytes. Might be why so many in the south do this.... – elbrant Feb 7 at 2:28
1

I use an old trick learned from the deep south (of the US) to make iced tea. The tannins in tea turn cloudy when poured over ice, so many would use a pinch of baking soda during the brewing. The resultant strong hot tea could then be poured over ice and would not turn cloudy from the tannins. I still use this trick on some black teas that I like since I am more sensitive to bitter than most.

Call it about 1/4 teaspoon per cup.

1

Add a little lemon juice to your tea and it neutralizes the tannins. You can also use soy sauce, but the flavour may not be so great afterwards.

  • You just threw so many concepts in here that sound interesting. Please will you unpack everything a bit more (and to stay on topic, especially go into your experiences regarding sensitivities to tannins and caffeine)? – Roman Feb 7 at 17:01

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