Reducing caffeine (pre-soaking)

Caffeine - yes, up to 80% in those 30 seconds. Slows down considerably after that so there's no appreciable benefit in extending the time. I don't go over 40-45 seconds if I can help it because too much flavor is lost with black teas. Steep as usual except only for about 30 seconds and discard water. Add more water to steep for drinking.

Flavor - depends. Usually varying degrees of yes for black. You'll have to experiment because it depends on the tea. Since multiple infusions are more typical for green teas, not really.

This is wishful thinking and an oft repeated tea myth that could well do with laying. I reproduce below a posting I made on Teamail some years ago - but I have seen no data to the contrary since:

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After some intensive Internet trawling (nay, dredging) and poring over a mish-mash of half truths and myth (and some of my own caffeine data regurgitated without attribution or comprehension) I have now found the level of data that I was advocating earlier this week - a peer reviewed scientific paper recording precise time related extraction of caffeine from tea using a modern detection technique (HPLC). This paper "Tea preparation and its influence on methylxanthine concentration" by Monique Hicks, Peggy Hsieh and Leonard Bell was published in 1996 in Food Research International. Vol 29, Nos 3-4, pp.

325-330. (FRI is copyright of the Canadian Institute of Food Science and Technology).

In summary Hicks et al measured the caffeine and theobromine (total methylxanthine) content of six different teas (three bagged and three loose leaf, including black, oolong and green types). They measured caffeine extraction in boiling water at 5 minutes (69%), 10 minutes (92%) and 15 minutes (100%). They replicated all their extractions three times to eliminate error. Extrapolation of their data below 5 minutes gives the following caffeine extraction percentages (averaged over all tea types and formats; note while loose tea extracted marginally more slowly than teabag tea it made only a couple of % points difference):

30 seconds 9% 1 minute 18% 2 minutes 34% 3 minutes 48% 4 minutes 60% 5 minutes 69% 10 minutes 92% 15 minutes 100%

This is very much at odds with the mythical "30 or 45 second hot wash to remove 80% of the caffeine" advice - as a 30 second initial wash of the tea will actually leave in place 91% of the original caffeine!

I commend the paper to anyone seeking further data.

If anyone has better evidence (based on actual analysis) about the efficacy or otherwise of hot water decaffeination I would very much like to hear it.

Nigel at Teacraft

messagenews: snipped-for-privacy@a75g2000cwd.googlegroups.com...

those 30 seconds. Slows down considerably after

Thanks, Nigel, for taking the trouble to swat down this endlessly recurring rumor!

This may seem like a small point, but I wonder if "boiling water" here means water that was boiled or water that continues to boil for the duration. At 15 minutes that could make a big difference.

/Lew

Fascinating, thank you for the reference, Nigel. The paper itself has some interesting conclusion. In the following, I use "black tea" in its Western sense, as in the paper (these being the usual Kenyan/ Ceylon/Assam varieties used in Lipton blends).

- Wulong (Taiwanese) was found to contain more caffeine in typical brews than loose-leaf black tea. This was because the brewing parameters for each type of tea were taken from the tea packaging, and the wulong packaging suggested using more leaf. Personal experience supports this - I tend to use more wulong leaf than darjeeling/assam/ hongcha/pu'er (though you, of course, may not!).

- Caffeine-per-gram was highest in loose-leaf black and green teas (identical at 36.6 mg caffeine per g of leaf), with less in loose-leaf wulong (28.8 mg / g). This is supported by the oft-touted conventional wisdom that black teas contain high caffeine quantities - though I was surprised to see that the loose-leaf green (a "Korean") was similar.

- Bagged teas were seen to contain less caffeine than loose-leaf tea in the initial (5 min) infusion, rapidly tailing off to caffeine levels of bagged tea being *much* less than loose-leaf tea in subsequent infusions. However, the authors noted that the bagged tea only retained their flavour for the first infusion (heh).

- Wulong lost its caffeine the fastest of all the loose-leaf teas, but all teas had >65% caffeine left in the leaves after the 1st infusion.

Note that the brewing method was placing the tea into boiling water and infusing for 5 mins without keeping the water boiling! This was intended to simulate slower "Western" brewing.

Previous studies recommened drinking "10 cups of tea per day" in order to protect against cancer. This was recently echoed by the BBC in an article that I linked here. However, this is (as the authors state) quite misleading: if one takes 10 cups of tea brewed "Western" style, using teabags, and not re-using them, the caffeine intake is pretty huge. It's way over the 300 mg / day limit that induces "headaches, nervousness, irritation" and other health problems. Drinking 10 cups of reinfused loose-leaf tea did not result in such high caffeine intake (~

I think real world experience will vary. My basic brewing parameter is adding boiling water for three minutes in 1/2L pot for any tea. The first pot is the euphoric hum with an occasional oolong and green which might make a second pot tasting flat but no buzz. I think smaller pots saturate faster limiting extraction while I go for the gusto in the first pot. I know I don't leave 50 percent of the caffeine in the pot. Don't sip tea. Coat your throat and warm your stomach.

Jim

...I don't gamble in Lost Wages....

I think it's safe to say that this is because oolong is typically made from big, mature leaves. Caffeine content is higher the closer a leaf is to the growing tip. Decent greens and blacks are made with leaves close to the bud.

/Lew

I can't comment on the second sentence, because I'm not sure how the caffeine content in leaves varies from tip to "xiaozhong", but I don't know how safe it is to say that wulong is made from big, mature leaves

- there's a significant amount of "tippy" wulong for sale from the Usual Suspects that I rather enjoy.

I definitely agree that good greens and blacks are tippy - as long as we restrict our definition of "black" to the western definition. There are some great Mainland hongcha varieties that are large in size, and clearly pu'er can be very large (depending on which "colour" one assigns to pu'er!).

Most surveys quoted on this forum, and on other sites around t'Interweb lists green teas as being the "low caffeine" alternative. I was somewhat surprised to see the results shown in this paper, in which the "Korean" was almost exactly the same in caffeine concentration as the black leaves. Perhaps all that is needed is a larger sample size in this case. What say you? It certainly seems to fly in the face of received wisdom (and in the advertising of many tea merchants). :)

Addio addio,

Hobbes

I'm sorry if I left the impression that there'd be no exceptions.

Yes, but when you're talking about the Yunnan Da Ye cultivar, Tippy doesn't necessarily Small.

See, for example,

/Lew

Good point Lew. The Holy Mountain data shows just how flawed is the "received wisdom" on caffeine. Their data indicates it to be (on average) neither higher nor lower in white, green, black or pu'erh. Caffeine differences are principally due to genome (China type - tend lower, or Assamica type - tend higher) or to nutrition (N makes caffeine higher), to season (fast growth makes caffeine higher) and to manufacture (can manipulate it up or down) - all these inlences can act together or against each other .

If I may again quote from another posting I made on Teamail (30th July

2004) in reply to some muddled thinking.

Teamail Quote>>>>>>>>>>>>>>>

The subject of caffeine in various types of tea has come up again. Last time it surfaced I couldn't locate the data, but now here is what I have.

Experimental process runs (were) undertaken in the Teacraft ECM System for precision miniature tea manufacture "the tea factory in a box". This system allows any environmental variable to be controlled to a set value while the other variables are held rock solid - and gained the American Society of Agricultural Engineers' AE50 Award for "outstanding technological innovation". Too expensive for home use, I fear.

1. Effect of wither conditions on caffeine level - same leaf into all experimental conditions, all leaf 2L&B standard, one named clone. Fast wither (8 hours to 70% moisture content) Wither at 15 deg C caffeine 3.20% Wither at 25 deg C caffeine 3.45% Wither at 35 deg C caffeine 3.30 %

Slow wither (18 hours to 70% moisture content) Wither at 15 deg C caffeine 3.10% Wither at 25 deg C caffeine 3.65% Wither at 35 deg C caffeine 3.43 %

A quadratic response in each set.

1. Effect of length of wither on caffeine level (hours to 70% moisture content) each run replicated - 2L&B hybrid seedling leaf used.

10hr 3.20, 3.23% = 3.22% 14 3.38, 3.41% = 3.40 18 3.38, 3.47% = 3.43 22 3.50, 3.52% = 3.51 30hr 3.53, 3.58% = 3.56%

Straight line response, no effect of wither moisture level, best response at 25 deg C

1. Effect of fermentation duration (minutes) on caffeine level (average of four clones)

0 3.20% 30 3.02 45 2.98 60 2.88 75 2.80 90 2.72%

Straight line response

1. And a little hard data from another source: Seasonal variation in % caffeine level - Kenya Dec Apr Jul Sep Clone 1 2.9 2.4 1.4 2.4 Clone 2 3.1 2.3 1.5 2.6 Clone 3 3.2 3.1 1.8 2.7 Clone 4 4.0 3.9 1.9 2.9

Absolute min/max Caffeine range through year Clone 1: 1.2 & 3.2% Clone 2: 1.3, & 3.4% Clone 3: 1.7 & 3.9% Clone 4: 1.9 & 5.0%

Qusetion - Is Clone 4 a high or low caffeine type?

I have shown here a few of the factors that can change and determine caffeine level in a made tea. Other important factors are level of nutrition (goes up with nitrogen) and degree of leaf shading.

All of which goes to show that quoting any particular caffeine percentage for a given tea type (and many people do) should be fringed with caveats and exact data given as to how it was processed and when it was grown. In the main none of this information is available to the producer, let alone the seller.

Which all goes to show that caffeine levels quoted either in sweeping generalizations or as absolute truth should be laughed at - at best (using HPLC analysis) a precise and accurate caffeine content is but a snapshot in time.

Nigel at Teacraft

Sorry. I haven't been keeping track of this thread.

I first learned of the 30 sec. decaf process back in '98-'99 and was given the source reference. As it was so long ago, I can't remember it. As I'm not at home, being on a long road trip, I'm not able to provide it.

Perhaps the OP or any other interested parties may want to contact the various tea vendors who advocate this DIY method. Upton's, for example, usually cites references for their articles and may be willing to provide their source for this info, too.

Thanks for your post, Nigel.

The only way to fly. Too bad they didn't take a few more low-time data points, but it's enough to make the lesson clear, as you indicate.

When plotted with the origin, these make a pretty typical-looking extraction curve. I would draw an even stronger conclusion than Nigel from the low-time interpolated data. Since the authors used powdered tea, extraction kinetics only model part of what happens in normal use. In particular, for the first several seconds of steeping, leaves are imbibing water rapidly, and very little material is leaving the leaf. So a real-life extraction curve is sigmoidal (S-shaped), with almost nothing happening for a period of time that might approach 15 seconds for some unbroken leaves.

I'm just a chemist; Nigel's the tea-science guru here and I defer to him. I suspect that we agree, though, that rinsing to remove caffeine will only work at all on CTC-type fragments where much of that component is in fast-dissolving dried juices outside the cellular structure. In this case, desirable flavor and alleged healthful effects will depart as fast as caffeine. With whole-leaf teas, the notion that caffeine can be removed selectively makes little theoretical sense, and the present result supports that.

Many years ago, I had the un-original idea of using ice-water to extract caffeine while leaving everything else intact. It doesn't work, since many important flavor components are about as soluble in cold water as is caffeine. Amino acids and sugars are examples. What doesn't come out so fast is astringent tannins, which is why some of us prefer cooler brewing styles. I think it fair to say that there is at present no practical way for the average home user to decaffeinate high-quality tea. It certainly could be done, by all sorts of affinity sorption techniques, perhaps embodied on a stick or straw. But I doubt that anyone will spend the development money to achieve this unless a lot of tea-drinkers present a collective marketing case to the biochemical and foods companies that command this technology.

-DM

I don't think the numbers are reproducible with the English or Gongfu styles of making tea. Just more meaningless factoid science.

Jim