EDITOR'S NOTE: When it comes to the topic of caffeine in tea, there is no end to the generating of myth and indeed of science fiction. Perhaps the most persistent canard is the one that alleges that tea can be 'mostly' decaffeinated (80% is, I think, the number most often quoted) by a quick preliminary infusion in hot water (30 seconds is the duration typically recommended). While one cannot hope to dispel so-called 'common wisdom' overnight, even by the demonstration of clear scientific fact, it is surely a step in the right direction to put the data into public circulation. That is why I have asked Nigel Melican, founder and Managing Director of Teacraft Ltd, to offer us a post on this and other aspects of caffeine in tea. Nigel is, quite simply, one of the world's leading authorities on tea; readers of CHA DAO will recall with pleasure the massive work of bibliography that he contributed to this blog in an earlier post; today's entry is, I think, destined to become a standard compendium of information on the topic.
Tea contains two physiologically active compounds: caffeine and theanine. Moderate caffeine consumption is perceived by some in western countries to border on the dangerous, and many consumers, rather than abstaining entirely from drinking tea, maté, or coffee, demand a decaffeinated version. In the case of tea, this is provided commercially by a process that uses organic solvents to remove most of the offending caffeine (along with other compounds); the result, unfortunately, is at best an indifferent product. (Ironically, the very caffeine so removed is a valuable by-product eagerly sought by soft-drink manufacturers to enhance their sugary beverages.)
As well as reducing product quality, commercial decaffeination is an expensive process that takes hours of production time and doubles the raw material price of a pound of tea. How likely is it therefore that the accountants at Lipton and similar packers would have overlooked a simple and inexpensive process that removes 80% of caffeine in 30 seconds? Yet this myth exists and is propagated daily by retailers and tea gurus without any other basis than that they wish it were true, therefore it must be. So: what, then, are the facts?
In 1996, Monique Hicks, Peggy Hsieh and Leonard Bell published 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,' appeared in Food Research International Vol 29, Nos 3-4, pp. 325-330. (FRI is copyright of the Canadian Institute of Food Science and Technology). Methylxanthines caffeine, theobromine and theophyllin all occur in tea and have similar physiological action, but in tea caffeine is the prominent methylxanthine.
In summary: Hicks et al measured the caffeine (plus theobromine) content of six different teas (three bagged and three loose-leaf, including black, oolong and green types). They measured caffeine-extraction in boiling water when steeped for 5 minutes, 10 minutes and 15 minutes. They replicated all their extractions three times to eliminate experimental error. Extrapolation of their data gives the following caffeine-extraction percentages below 5 minutes (averaged over all tea types and formats); note that while loose tea extracted marginally more slowly than tea-bag tea, it made only a couple of percentage-points' difference:
30 seconds: 9% caffeine removal
1 minute: 18% caffeine removal
2 minutes: 34% caffeine removal
3 minutes: 48% caffeine removal
4 minutes: 60% caffeine removal
5 minutes: 69% caffeine removal
10 minutes: 92% caffeine removal
15 minutes: 100% caffeine removal
Clearly to achieve the 80% target we must wash our tea for more than five minutes! 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!
Before the publication of this work by Hicks et al, Professor Michael Spiro and his group had already done some ground-breaking physical chemistry on tea. In their paper, 'Tea and the Rate of Its Infusion' (published in Chemistry in New Zealand 1981, pp 172-174), they disclosed caffeine concentration diffusing into water (4g loose leaf -- it will have been a CTC small fannings type -- in 200 ml water held at a constant 80 degrees C, and stirred with a magnetic stirrer). Their first data point is at 90 seconds, and shows 49% caffeine removed from leaf (i.e. into the wash water). Extrapolating from Spiro's plot gives:
30 seconds: 20% caffeine removal
1 minute: 33% caffeine removal
2 minutes: 64% caffeine removal
3 minutes: 76% caffeine removal
4 minutes: 85% caffeine removal
5 minutes: 88% caffeine removal
10 minutes: 99% caffeine removal
15 minutes: 100% caffeine removal
Again we would have to be washing our tea for a long period – three to four minutes to achieve 80% decaffeination. While a 30-second 'wash' under Spiro's rather extreme laboratory conditions (small leaf CTC tea, loose in the 'pot' rather than in a teabag, at constant temperature and stirred vigorously) leached 20% of caffeine rather than the 9% yielded by Hicks's more normal steeping, neither of these scientifically conducted findings comes anywhere near the 30-second/ 80%-decaffeination claims perpetuated as an Internet Myth.
Another much-repeated claim is that black tea is high in caffeine, green tea is lower, and white tea (through the naturalness of its manufacture it is implied) has next to none. While suiting the sales pitch of some tea vendors this information is so wrong as to verge on the fraudulent.
Three scientifically verifiable facts are:
1. Caffeine level varies naturally in types of tea and levels in one type may overlap with another type
2. Black and green tea manufactured from leaf from the same bushes on the same day will have virtually the same caffeine levels (within +/- 0.3%)
3. For a given bush, the finer the plucking standard, the higher the caffeine level
Actual caffeine level in tea is highest:
• when the tea is derived from buds and young first leaf tips (thus white tea has a high caffeine level)
• when the bush is assamica type rather than sinensis (can be 33% higher caffeine, thus African black tea tends to be higher than China black tea)
• when the bush is clonal VP rather than seedling (can be 100% higher caffeine, thus new plantings in Africa are higher than old seedling plantings in Asia),
• when the plant is given a lot of nitrogen fertilizer (as in Japan), and
• during fast growing seasons.
Thus tea derived from older leaf, China type seedling bush, under-fertilized husbandry and in autumn season will naturally be lowest in caffeine. Georgian and Turkish tea falls into this category: expect only 1 to 1.5% caffeine in them, compared with the usual 3% in retail teas. Tea from well-fertilized fast-growing young tips of African clonal tea can often have 5-6% caffeine.
The above summary disregards the changes in caffeine level (albeit smaller than genetic, edaphic and climatic mediated changes) produced during tea processing. Those interested in the topic of caffeine levels in various types of tea may be interested in some experimental process-runs 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.)
EXPERIMENT 1: Effect of wither conditions on caffeine level. The same leaf was put into all experimental conditions; all leaf was fine 'two leaves and a bud' standard; and was a named VP clone.
Fast wither (8 hours to 70% moisture content):
Wither at 15 degrees C: caffeine 3.20%
Wither at 25 degrees C: caffeine 3.45%
Wither at 35 degrees C: caffeine 3.30 %
Slow wither (18 hours to 70% moisture content):
Wither at 15 degrees C: caffeine 3.10%
Wither at 25 degrees C: caffeine 3.65%
Wither at 35 degrees C: caffeine 3.43 %
A quadratic response in each set, with the highest caffeine produced by slow wither at moderate temperature (also, by gut feel, the tea maker’s favorite conditions) and demonstrating that the field is not the only determinant of caffeine level in the cup.
EXPERIMENT 2: Effect of length of wither on caffeine level (hours to 70% moisture content). 2L&B hybrid seedling leaf was used; each run was replicated and the means are also shown.
10 hours: 3.20, 3.23% = 3.22%
14 hours: 3.38, 3.41% = 3.40%
18 hours: 3.38, 3.47% = 3.43%
22 hours: 3.50, 3.52% = 3.51%
30 hours: 3.53, 3.58% = 3.56%
Straight-line response, with long withering producing the highest caffeine by 0.34% over slow wither.
EXPERIMENT 3: Effect of fermentation (oxidation) duration (minutes) on caffeine level (average of four clones).
0 minutes: 3.20%
30 minutes: 3.02%
45 minutes: 2.98%
60 minutes: 2.88%
75 minutes: 2.80%
90 minutes: 2.72%
Again, a straight-line response with oxidation, unlike caffeine boosting withering, slightly reducing caffeine level in black tea. Note i) that green tea is neither withered nor oxidized, and ii) white tea is not oxidized but has a very long wither
FIELD DATA: Some hard data from published sources
Seasonal variation in the natural caffeine level of Kenya Tea clones averaged for the four quarters:
Here caffeine level is lowest in all the clones during the slow growth period of July. (Note Clone 4 variation of more than 100% from slow growth season to fast growth in December quarter.)
Again from Kenya, consider the absolute minimum/maximum caffeine measurements through the 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%
These natural variations across time make it difficult the assess whether a particular tea or tea-type is a high-caffeine or low-caffeine type, particularly with a single 'snapshot' analysis, as is often listed even by enlightened vendors on the Internet. For example, should we consider Clone 4 a high- or low-caffeine type?
I have shown here a few of the factors (natural and man-made) that can change and determine caffeine level in a made tea. Other important factors that influence the level are the level of nutrition (which goes up with nitrogen in the soil) and the degree of leaf shading which increases caffeine (though it is applied, in Japan, to increase theanine).
All of this goes to show that quoting any particular caffeine percentage for a given tea type, as many people do, should be fringed with caveats, and the exact data provided as to how it was processed and when it was grown. At best (using HPLC analysis), a precise and accurate caffeine-content measure is but a snapshot in time. And in the main, none of this information is available to the tea producer, let alone to the seller.
Any solvent used to remove caffeine will also remove other chemical compounds from tea. The completely-targeted solvent does not exist, though some are better than others. Antioxidant polyphenols (flavanols) -- present as catechins in green tea, and in black tea either as oxidised catechins (= theaflavins) or as condensed polymerised oxidised catechins (= thearubigins) -- are partially soluble in the decaffeinating solvents, though as you would expect these are chosen to maximize caffeine solubilty and minimize polyphenol solubility. Typical data is 82% removal of polyphenols by (less expensive) ethyl acetate decaffeination, and only 8% by (more expensive) supercritical CO2 decaffeination.
The methylene chloride solvent route is not allowed by the FDA for tea decaffeination (though bizarrely it is for coffee!). It is however permitted and used in Europe, and the polyphenol retention is midway between that of ethyl acetate and of supercritical CO2. Probably the best decaffeinated tea is made by applying the extraction process during tea manufacture, rather than after it. This is done in a few factories in Malawi and Zimbabwe, and produces a decaffeinated cup that is virtually indistinguishable from normal tea from the factory. Such decaffeinated tea does not appear in the USA for several reasons: it is a CTC process; the robust colour and taste demand milk; and it utilizes methylene chloride solvent.
Consumers demanding decaffeination for the sake of their health or their sleep have I suspect been subjected more to caffeine excess from coffee than from tea. Coffee-, maté- and cola-derived caffeine can deliver a jolt that tea, be it ever so strong, does not deliver, though when extracted the caffeine from all these sources is chemically the same. The natural complexing of caffeine in tea (it binds with tea polyphenols during steeping) gives a slower and more gentle uptake in the stomach and hence to the brain; and I suspect that the relaxing effect of tea's own mind-calming amino acid (theanine) also contributes to the body's reacting more gently to tea caffeine than to coffee caffeine.
http://nobleharbor.com/tea/caffiene.html [sic]
This page supports the information given above – summarizes the Hicks et al paper, and in places borrows some of my own data, with a few (unimportant) errors. It debunks some of the popular caffeine myths and concludes 'all teas have roughly similar caffeine contents, and one cannot rely on the belief that green tea has less caffeine, as asserted by many popular claims.'
http://lpi.oregonstate.edu/infocenter/phytochemicals/tea/
The Linus Pauling Institute gives a fairly inconclusive comment on the level of caffeine in tea showing data (from just 20 snapshot analyses) that the green teas they analyzed varied from 40 to 211 mg/liter, while the black teas varied from 177 to 303 mg/liter -- a larger and more representative sample of the worlds teas could have would have increased these ranges and the overlap considerably. However, LPI do suggest that the popular belief of low caffeine level in White Tea is misplaced: 'Buds and young tea leaves have been found to contain higher levels of caffeine than older leaves, suggesting that the caffeine content of some white teas may be slightly higher than that of green teas.'
A wonderfully well-written and enlightening article. Thanks for posting!
ReplyDeleteI don't understand why they didn't test the caffeine content when the tea had steeped for 30 seconds. Testing after 5 minutes and then attempting to extrapolate the data for shorter steeping times doesn't make sense to me.
ReplyDeleteMark
How do they know that 9% was extracted at the 30-second mark? Maybe 60% was extracted in 30 seconds and then another 9% was extracted over the next 4 1/2 minutes. Am I missing something?
ReplyDeleteMark
Mark -
ReplyDeleteWere I to plan an experiment to specifically check caffeine extraction at 30 seconds I would of course measure at 30 seconds and times around it. In the absence of the quite substantial funds for HPLC analysis of caffeine one has to fall back on published data; this is scientifically valid. In the absence of data from the "rapid water decaff camp" I must use general decaffeination data - the two sources I cite are Hicks et al and Spiro. Hicks first data point is at 5 minutes, Spiro at 90 seconds. Extrapolation is a valid scientific method (in fact it is interpolation here because we know that extraction at zero time is zero, and we know the value at the first data point. We also know that typical extraction follows a diminishing returns polynomial shape, therefore it is reasonable to use this shape of curve during interpolation.. It is totally unreasonable to believe that 60% was extracted at 30 seconds but only 9% over the next 4.5 minutes - extraction, from experience does not work that way.
In short, yes the extraction data should be collected through the time (30 seconds) under dispute - but as no-one has done this (though they claim the effect as though they had) then we have to use the available data as best we can to try and extract the truth as well as the caffeine.
Nigel at Teacraft
Umm, so if I steep my tea for 4 minutes, I don't get 40% of the caffeine? (that is, I get 60%.) That surely seems like the most effective means of reducing caffeine!
ReplyDeleteI'm only half-joking -- at what point in the steeping do they consider it "done" and is that then called the caffeine content?
Jen -
ReplyDeletethat's correct, 60% into your cup under the conditions of Hicks' extraction - i.e. not stirred. Under Spiro's extraction (mechanically stirred) you would have 85% of the caffeine in your cup after 4 minutes.
When a steep is "complete" depends very much on you - how strong you like your tea, how hot your water, what weight of tea, how big your pot, the type of manufacture, the particle size of the tea, its genetic origin, how hard the wither was, etc, etc. Caffeine content is assessed on dry leaf and the percentage extracted in any given time relates to that amount. As a scientist I am absorbed by the subject but as a tea lover I totally ignore all this kefuffle about caffeine when making tea and just make it to please me.
Nigel at Teacraft
Thanks for the piece, Nigel.
ReplyDeleteSpeakin of Kenya... is the problems there going to affect tea prices? I konw they're a big exporter these days
It is very exciting to find scientifically backed up information on tea in this world plagued by publicity-induced myths. Thanks so much Nigel for your fantastic job. I hope that some day I will be able to contribute to the world of tea as you have. Saludos!
ReplyDeleteJuandiego
-SenchaSamurai-
As with many discussions of the healthful benefits of tea, caffeine in tea is a topic that inevitably generates confusion, inaccuracies, and debate. Often the assumptions, ‘facts’ and criteria offered to support what are supposed to be ‘truth’ are so invalid that no solid conclusions can be reached at the end of the discussion and the reader ends up being more confused than enlightened.
ReplyDeleteSo it was with trepidation that I began to read the posting above on caffeine and decaffeination. Pleasantly, though, this discussion is one of the better that I have seen, especially on the Internet.
I do have several salient points to add, in the hopes that the more and better the information available, the better tea lovers will be able to enjoy this delicious pleasure beverage. While doing the research for the caffeine section of our book The Story of Tea, A Cultural History and Drinking Guide, Ten Speed Press October 2007 I had the opportunity to re-examine many of the facts that have been thought to be true over the 35 years that I have been involved in the coffee, tea and cocoa business. I found it interesting that the vast majority of information and data regarding caffeine in coffee and tea, and humans’ consumption of caffeine has not changed much in the light of current science or lifestyle. I think the biggest difference today is likely the size of a cup of coffee. A ‘cup’ of coffee today has certainly doubled in size and is often 3-4 times that of one consumed just 20 years ago. That ‘cup’ has gone from a standard 5½ oz. to at least 10-12 oz. or very often 16-20 oz or larger. This of course changes the data regarding actual coffee caffeine consumption. Tea caffeine consumption however, does not seem to have changed as much, if at all, because the size of a ‘cup’ of tea has not increased and in fact may have decreased, as more tea enthusiasts use Asian-style cups or steep teas that require multiple infusions. So the 5½ oz. cup of tea is still the standard in the marketplace.
First and most importantly, let us remember that tea was designed by Mother Nature to have caffeine in it – indeed it is caffeine that is demonstrably the primary reason that tea (and coffee, cacao, and mate) became popular beverages.
That being said, the desire to alter the natural fact of caffeine in tea has led to a variety of possibilities that sometimes works out and sometimes doesn’t. As pointed out rarely in discussions of this type, the most obvious way to reduce one’s caffeine consumption is simply to not consume caffeine–containing beverages. Alas, although this is not a modern thought, it is 100% effective, has no side effects, and is cost-free. The coffee industry struggled with the questions surrounding caffeine many decades ago and I would hope that their experiences will make the tea-lover’s questions about caffeine be resolved more quickly, as much of the research and probability has already been done. In fact, I would not be surprised to see soon the same phenomenon with tea as has occurred with coffee: the introduction of a super-caffeinated version! I would propose that there are as many (or more) consumers who desire tea with more caffeine in it than Mother Nature intended than there are those who would select a decaf version of tea.
One important distinction that must be made is the difference between caffeine reduction and decaffeination. Decaffeination has a legal definition, and that is that 97% of the caffeine that was present before processing must no longer be present following processing. This, of course, really doesn’t tell the consumer very much at all on the one hand – how many casual tea or coffee drinkers really know (or care) how much caffeine they intend to, should, or already have consumed in a given day? Caffeine is present in a multitude of beverages (both naturally and added, such as in soda) and some medications and is generally regarded as safe in the quantities that most healthy adults are exposed to in the course of a normal day of eating and drinking (such as 1-2 cups of coffee or 3-4 cups of tea). Let’s leave aside those who truly need to limit their caffeine intake for medical reasons and focus on those who simply want to have a second cup or want to moderate, but not eliminate, caffeine from their tea. This is the reason why the process of steeping tea leaves has enjoyed attention as a possible means of adjusting the ultimate amount of caffeine suspended in the liquid beverage. Two observations have been made in this regard: one is that a quick steeping of certain tea leaves will release a majority of the caffeine fairly readily, and the second is that a particularly long steeping time will negate the absorption of caffeine from the liquid. Both are valid to an extent, and impossibly inaccurate at the same time.
Let’s examine the quick-steeping method that is valuable but so hard-to-prove scientifically. It seems to be valid that fully-oxidized orthodox leaf black tea, when steeped in very hot water for a period of up to a minute will release the majority of its caffeine and some of its natural colour during that time period. As a means of reducing caffeine content in the finished brew, this is a reasonable method for the consumer to employ. No one of any repute in the tea industry that I am aware of has ever suggested this phenomenon to be true for any other class of tea, so green, oolong, white, etc will not release its caffeine in this way. The ready-water-solubility of the caffeine in the leaf is the main factor here, and for orthodox leaf black tea, this procedure clearly works to a certain degree. Similarly, ctc black tea infuses more slowly than whole leaf, in large part due to the lack of immediately available surface area, and will not release its caffeine as quickly. Other variables exist which make the whole idea complicated, but do not necessarily invalidate the premise. Certainly it is a procedure that is not exact, but it is not proposed as science, only a method.
Nigel interestingly questions this method’s validity on the argument that decaffeinaters do not employ it. This argument is not fair; as of course those in the business of extracting caffeine from plant matter would not use such an inexact and unreliable method. If one is in the business of processing plant matter with the goal of obtaining 2 distinctly saleable entities: a decaf tea (with the required 97% of the caffeine removed) and pharmaceutical-grade caffeine, then plant matter that is anywhere from 50-80% caffeine-reduced is of negative value and the caffeine less plentiful than if removed more effectively. Similarly, ctc tea is not first choice for decaffeinaters either, as it takes too long to process. The caffeine extractors that I have spoken with test for high caffeine content and ready water-solubility, which usually means particular crops of recently-pruned, highly fertilized, machine-sheared tips of leaf processed into black tea (or at least oxidized in this manner – chances are that it is not particularly tasty!) It is interesting to note that industrially-extracted caffeine is extracted from fully-oxidized black tea and not the green ‘raw’ leaf; this indicates further that there is validity to the water-solubility theory. We are just starting to see decaf tea offered that is processed prior to manufacture, as is coffee, rather than after manufacture. It is more expensive than the traditional decaf tea, so it will be interesting to see whether or not this method will become popular.
In the case of coffee, depending on market particulars, it can be true at times that the extracted caffeine is more valuable than the decaffeinated coffee itself. Surely this must be the situation with a lot of the tea used for caffeine extraction. Where does that tea end up anyway? Perhaps in the sweetened bottled cold teas that have invaded convenience stores…
The second part of the discussion of quick-release is the 1996 Hicks study. This is so blatantly inappropriate as to be of no value. First, it includes several types of tea (black, green, and oolong, in both loose leaf and ctc, bagged form), second, it doesn’t use the time frame proposed (rather argues that extrapolation is okay), and averages everything out for its results.
While I understand the difficulty in proving the concept of the quick-release caffeine method, this study, which was done for other scientific pursuit, should not be used to refute it, as it just doesn’t apply. Studies analyzing the French Paradox studied French people eating foie gras and foods of the specific region under scrutiny, drinking red wine of the same region. A study conducted similarly in France with French people eating traditional Italian or Georgian cuisine, or drinking a mixture of red, white, and rose wines averaged together would not be considered specific to the idea being examined.
It would be of some value to actually conduct a scientific evaluation of the quick-release method of caffeine reduction, although as pointed out already in several places in this stream, results of this type of study would be limited to the parameters of the individual study and would not extrapolate out into practical application. The whole point of the method in question is that it is not scientific, only a potential reduction in caffeine in solution.
The long-steeping method of potentially reducing the caffeine in steeped tea is also worthy of note, as it explains the British pot-of-tea phenomenon. The observation has been made that the second (or third) cup of tea from the same pot from which the leaves have not been removed seems to have less caffeine in solution and those who sit down to enjoy a pot of tea do not get the ‘jag’ expected from so many cups of tea at a theoretically high concentration. This reduction is explained by the amino acids and polyphenols that take longer to extract into the steeped tea. When they do so, they can bind to the caffeine in solution, making the caffeine more difficult to absorb. This chemistry is well-documented, though also unpredictable to exercise in practice, due to many of the same variables as other tea-steeping chemistry situations.
None of this addresses the real issue, which is the caffeine content of the various classes of tea. This is where Nigel does an excellent job of explaining a few of the variables. It is excellent to have another voice promoting the realities of the composition of the tea leaf. It should be obvious that leaf processed from the same bush on the same day (no matter the style being processed) would have the same caffeine content, but most in the tea business would answer that question incorrectly. Even in clarifying and being accurate (see point 2 in the second section) while assam bush leaf tends to have a higher caffeine content than china bush leaf, chances are very good that the caffeine in that assam bush leaf will be less readily water soluble, so a cup of tea made with assam bush leaf may actually have less caffeine in it! There is just no end to the complexity of this topic, as my fun ‘quiz’ on pages 362-3 of The Story of Tea demonstrates.
I always love to point out that the one thing that can be said for certain is that tea does contain caffeine. It is interesting to note that in large part due to the complexity of the discussion in hand, the emphasis in the tea trade regarding decaf (or reduced caffeine) tea is now directed toward a plant hybridized to reduce or eliminate the caffeine in the leaf. This is the best possible way to alter the content of caffeine in the beverage. A genetically-modified tea bush would be a far better solution to the decaf question than the myriad solvents and processes that are used today. Of course once again, there is the idea of choosing an alternative beverage, which is the best answer that we have today.
What I find most exciting about all this is the superiority of nature over manipulation. I do not foresee the day when tea in the marketplace will have ingredients or chemical composition labeling – it is just too complex, unpredictable and unnecessary. Consumers will just have to learn a little bit about tea and pay attention to what naturally occurring compounds are in the leaf.
Finally, in agreement with Nigel’s sentiment: I would rather leave the science to those whose job it is to analyze these things, and just enjoy the pleasure of a cup of great tea.
Thanks to Cha Dao for posting the discussion,
Bob
Bob –
ReplyDeleteThanks for your elegantly composed comment on my Caffeine – Myth and Reality. Our views are not a million miles apart in general – for example the first and last third parts of your commentary, though I do disagree on some of your specific assertions in the middle third.
• The quick steeping method is “so hard to prove scientifically” – no, given the funds very easy to prove/disprove – nobody yet has done the specific work to support the market claims.
• “CTC black leaf infuses more slowly than whole leaf” – no, no, no! The entire quick brew teabag industry is utterly dependent on CTC’s fast infusing characteristic – it’s why orthodox tea production has declined to 40% from 100% in 40 years. CTC’s smaller particles, macerated cells, dried expressed tea juice all give very rapid extraction of color, flavor – and caffeine.
• Not fair to say the steeping method is invalid because decaffeinators do not use it – in fact decaffeinators have tried to use it (water decaffeination), most recently in India. For coffee it works, for tea it produces such a poor product it cannot even match solvent decaffeination.
• The Hicks study is “so blatantly inappropriate as to be no value”. This study supports the Spiro study. Together they represent the ONLY timed tea caffeine extraction data publicly available and, however limited they may be, together they indicate that 80% removal in 30 seconds is not so - yet the 30 second steepers refute these findings without undertaking the study that would support their claims
• The Hicks study “averages everything out for its results” – Hicks does not do this; their individual data for loose leaf and tea bags, black, green and oolong tea shows similar trends for all – averaging is therefore valid. The averaging however is mine for conciseness.
• The quick steep method is not intended to be scientific, “only a potential reduction in caffeine in solution”. Yes, Bob, but it is being promulgated in a myriad websites as actual fact with specific times quoted and specific percentage reduction indicated – that sounds scientific to me.
• The British pot of tea phenomenon – if the third cup appears, anecdotally, to have less caffeine it may be more to do with the British habit of topping up the pot with more hot water.
• Polyphenols bind to caffeine making caffeine more difficult to absorb – “this chemistry is well documented”. Yes, it is but unfortunately the extraction rates are not documented.
• “chances are very good that the caffeine in that Assam bush leaf will be less water soluble” than China bush leaf. In 30 years of working with tea makers and tea chemists, I have never seen any evidence that would support that view.
But to return to areas of mutual agreement – your Caffeine Quiz in “The Story of Tea” does illustrate memorably the complexity of knowing exactly what caffeine is in your cup- even if you knew what caffeine was in your dry tea.
Nigel at Teacraft
I understood why you want to explore Tea in Hong Kong and China very much now ! I found you are a expert in tea!!!
ReplyDeleteCherry met in the plane
wow, this is a quite eye opening article. I always heard the whole 30 seconds and you have decaffeinated tea thing, and if this study is valid I guess thats just all a tea lie. Interesting, but I never actually did the 30 second decaf thing so I guess this doesn't effect me to much..
ReplyDeleteThank you Nigel for a very interesting and informative discussion of the myths surrounding the caffeine content of teaas. I have been sorely misinformed over the last several years (and must confess myself guilty of misinforming some others). And thank you to Robert Heiss for the interesting counterpoint!
ReplyDeleteAt least now we know that one can not decaffeinate the usual tea that easily. Thanks for your work Nigel.
ReplyDeleteby Nigel:"– in fact decaffeinators have tried to use it (water decaffeination), most recently in India. For coffee it works, for tea it produces such a poor product it cannot even match solvent decaffeination."
ReplyDeleteThis seems irrelevent (regarding Robert's view) to me, since extraction via the water method during manufacturing and a 'quick wash' with fresh from the bag tea are two very different methods. Keeping tea fresh is pretty hard already, without washing it with water possibly months before it's drunk.
There are at least three reasons I've heard of (I haven't been in this game long) to wash the tea prior to the main steep: removal of (bitter) dust and fine hairs; 'awakening' of the leaves to prepare (presumably) for a broad extraction of all the natural compounds; and as an added benefit the removal of some caffeine.
I usually wash only darker greens, oolongs, black teas and puerhs however, and that's only for a few seconds at a time, maybe 15.
On the whole though a very interesting article and a personal insight so thank you!
As to the broader question of caffeinated tea (such an odd pairing of words!), I just remember reading that the regular consumption of tea-caffeine is what is regarded by many in China to be a 'healthy addiction'.
I think whenever discussing this topic it is highly relevent to bear in mind the real-life scenario above all else, even when, rather especially when in the scientific context. I think retailers have simply extrapolated in a careless manor from the difference between 'Builder's Tea' and a carefully brewed green tea, to simplify the matter. Since Black teas are usually brewed at a significantly higher temperature than Green teas I think that comparing all three (the former two and Oolong teas) at the same temperature to be irrelevent also. Of course you have patiently mentioned the fact that these constitute the best scientific study data available, so my point is simply that the real-world debate has only just begun and the science will, unfortunately, always lag behind.
It has always been a slightly distressing experience to read a retailer's assertion of the caffeine content of a tea they sell, since the astronomical number of variables explained in part above were always in the back of my mind. The vagueness too is also interesting to note:
"Caffeine content: Low-Medium"
..useless!
In fact, that tea is sold as a health beverage at all slightly annoys me, but that is the condition upon which I receive any at all here in the West, so I suppose I have to live with it.
I don't think I have ever seen '80% removal after 30 seconds' assertions anywhere, but I've certainly seen claims which imply similar amounts and these have always seemed highly optimistic (depending on how you like your Yang).
Ian
Patent applications are full of claims that 80 per cent of the caffeine is removed after thirty seconds.
ReplyDeleteall the patents are for extraction in a factory using chemicals etc, they do not claim extraction via a 30 second steep using hot water
ReplyDeleteGood Job! :)
ReplyDeleteTwo of the three best things in life are sleeping and drinking tea, so this is a very interesting subject.
ReplyDeleteI question the logic of the water temperature of 80 °C in the steeping tests. The wikipedia article on caffeine says:
"Solubility in water
22 mg·mL−1 (25 °C)
180 mg·mL−1 (80 °C)
670 mg·mL−1 (100 °C)"
Which is a huge difference between 80 °C and 100 °C.
I rinse a very good thermos with boiling water, then put in loose tea in a T-sack and pour the boiling water over it. So I (pre)steep at somewhere around 95 °C. That could have a big effect on the amount of caffeine left over.
Another important variable would be the duration of the subsequent 'real' steeping. The question is not how much caffeine is removed from the leaves - all we want to know is how much in is the brew after a normal 5 or 6 minutes steeping.
I guess we need more testing.
Buying the tea and boiling the water are easy enough - how hard can it be to measure caffeine content?
This would be science that really matters!
Jeroen, a couple of points here to be clear about:
ReplyDelete1.Solubility data relates to 100% caffeine dissolving into water with no impediment and gives no indication of the time it takes to become soluble. Extrapolation from this condition is imprecise when you are trying to dissolve caffeine that is locked into leaf cells, at a concentration of just 3%, not 100%, and with a time element also involved.
2. Hicks used boiling water. Prof Spiro used 80 deg C. He was not trying to measure "magic decaffeination washing". He was studying the dynamics of tea extraction under normal British brewing conditions. Prompted by your post I measured brew temperature against time under four conditions, using a Telia sack and 5 grams of tea. I will not burden you with all the data but in summary:
Steel thermos, preheated, with boiling water: after 5 mins - 96 deg C, after 10 mins - 93 deg C.
Chatsford pot, preheated, with boiling water: after 5 mins - 85 deg C, after 10 mins - 81 deg C.
Chatsford pot, ambient tenp (17 deg C): with boiling water, after 5 mins - 82 deg C, after 10 mins - 76 deg C.
Porcelain mug (with teabag not Telia) ambient tenp (17 deg C), with boiling water, after 5 mins - 74 deg C, after 10 mins - 66 deg C.
Thus Prof Spiro's choice of 80 deg C very much reproduces the average temperature of typical British tea brewing which then was in an unheated temperature teapot and now (alas!) is in an ambient temperature mug.
Incidentally your chosen method: a pre heated flask giving prolonged brewing at elevated temperature is not the brewing condition that tea is manufactured for. You will extract moretea solids and faster and I would expect the brew to be more bitter and less complex than when "normal" conditions are used. Flask brewing is much the same is done in Indian tea shops where tea is boiled to get the maximum extraction - efficient but not excellent!
3. I do agree with you your last point. Yes, it is not hard to measure caffeine - all you require is an HPLC - the real problem is the expense (USD 20,000 for an in-house instrument plus the laboratory infrastructure). The last time I looked at outsourcing a caffeine measurement the quote was USD 350 per sample or USD 210 each for 10+ samples. Thus a very simple experiment - checking caffeine extraction of one just tea type at just one weight, in just one brewing vessel, at say 1 minute interals for 5 minutes, replicated x2, would cost USD 2,100. Imagine what the Hicks experiment would cost at contract rates.
Nigel at Teacraft
Hi Nigel -
ReplyDeleteYou are completely right about the physics. Also, I won't rinse my thermos before the second steep, thank you.
But how about this testing method?
http://www.discovertesting.com/products/display_products.sd?iid=3269&catid=7&loc=show&headTitle=Caffeine%20Test%20Strips
It's less than 1/1000th of the cost you mention - and needs just half a teaspoon of tea per sample to boot?
It only shows whether a solution has more or less than a certain %, but at that price, one could afford to try the broth after different dilutions.
Hallelujah! My doctor has ordered me to only drink decaf for the past year (I only drink tea, not coffee). I have a pantry FULL of caffeinated tea. This morning I took a chance of brewing a cup of one of my favorite black teas. Based on "word of mouth" info, I brewed for 3 minutes. I think I now have a good handle on the fact that I should brew for as long as possible and then sit back and enjoy. Is this right? Thank you SO much for this well-written article and to all those who entered into the dialogue.
ReplyDeleteThanks for this - very interesting post. Ian's brought up an extremely relevant point that you don't touch on, though - temperature clearly makes a huge difference to caffeine absorption (there is some published science on this, specifically with respect to tea, though not very much)... and the best temperatures for brewing different teas are well-known to be very different!
ReplyDeleteGreen tea is ruined by boiling water, one reason a lot of people say they don't like it - almost all of them have never had it brewed correctly! Black tea is not quite as bad when brewed with water well below boiling, though still pretty awful.
So testing all teas with standard temperatures, whether boiling or 80°C, tells us next to nothing about the content of a decent cuppa. I don't think it's anywhere near safe to assume that 80 Celsius is a good approximation of how English tea is brewed; even a few seconds at 90-100 might make a huge difference to the makeup of the tea - and the taste of a cup suggests that it probably does.
Fergus
ReplyDeleteI assume you mean rate of caffeine 'extraction' when you speak of temperature influence - in which case I agree the influence and I agree the lack of research into the effect of brewing temperature on removing caffeine from the dry leaf and presenting it in the liquor - hotter means faster - but no-one has measured how much faster. Unfortunately precise science cost a lot of money - while loose guessing is available to tea vendors for free.
Ian was referring to the real world - well, in the real world there is no doubt that caffeine extraction is slower in cooler water (even if we cannot say exactly how much slower), and in the real world, as you point out greens should see a lower water temperature than boiling. So, in the real world the "80% extraction in 30 seconds" myth would actually be even more mythical for greens than for blacks - yet it is for green teas that it is chiefly advised!
Nigel at Teacraft
I should point out that since posting that comment I have discovered from an author I trust that green tea can be brewed at boiling point with no increase in bitterness, if it is of the highest quality. Of course, with higher quality leaf you also get more caffeine, but substantially more theanine too.
ReplyDeleteYou might think I am trying my darnedest to find fault with your article, but this is not the case, as the myth it busts so completely I had not even heard of before. I googled it just now for amusement and found this (the only obvious and direct reference I saw though):
http://tinyurl.com/b6yulv
Also this wiki discussion you might want to pay a visit to, as there are some contradictions in the main article:
http://tinyurl.com/ard4mo
It is what your article implies in this Real World I speak of that really gets my interest, because the truth regarding caffeine in a cuppa is already in short supply, and to supply scientific but highly specific fact to those who might over simplify and then redistribute your findings to those who just drink tea in cups is worrisome (I'm pretty easy going though and am not actually that bothered...I just like discussion, especially about tea).
Specifically of interest to me is the relative caffeine in cups of different types of tea (Black, Oolong, Green, White and Puerh), brewed to an expert's recommendation, or preferably the retailer's recommendation.
I am not yet willing to concede that an actual cup of fine white tea has as much caffeine as a cup of CTC black tea, or even for that matter a cup of Chinese whole leaf black tea, on the back of this article. I do however wait for a convincing argument to prove it one way or another.
I would be very interested to see whether you dismiss any part of the following claim point-blank or not:
"White tea ...
Extremely low in caffeine, it can be drunk at anytime of the day or night."
"White tea contains approximately 8-16mg’s of caffeine per cup, the least of all teas. Known to contain higher levels of antioxidants than any other type of tea, it is recommended for everything that green tea is good for, the difference being that it is almost caffeine free. Chinese Medical Practitioners recommend it as a treatment for hives."
I have quoted this page:
http://jingtea.com/tea/white-tea
Of special note is '8-16mg’s of caffeine per cup', versus '45-60mg's per cup' for black tea:
"Black tea contains approximately 45-60 mg’s of caffeine per cup. People with heart related problems are recommended to drink black tea since it improves blood vessel function, reducing the risk of heart disease."
http://jingtea.com/tea/black-tea
Green tea, if of poor quality, often tastes bitter, but I have never had this issue with white tea, it feels somehow less susceptible to bitterness (and therefore caffeine?), hence my interest here. I look forward to seeing what you make of it.
How much is tannin to blame for bitterness compared to caffeine?
Another thought on white tea which may sound like a wild guess (it is), but assuming for a moment that a cup of white tea does contain less caffeine than a cup of, say, green tea, brewed at the same temperature for the same time, could it be because white tea is withered and not rolled, and therefore leaves the cell membranes intact and thus inhibits caffeine extraction?
ReplyDeleteIan
ReplyDeletePlease do not assume for even a microsecond that white tea, in the leaf or in the cup, contains less caffeine than green. There is no such thing as a typical tea for caffeine content - but as a generality whites are a shade higher than greens and blacks are often a tad higher than whites. Further than that on concrete evidence or on rational extension, you cannot go.
Claims for low caffeine in white tea are vendors' mendacity - not fact (even fact to be 'wildly guessed assumed for a moment').
Nigel at Teacraft
Nigel,
ReplyDeleteLet me thank you for your discussion and posting related to caffeine and tea. I have had parts of this discussion with authors and scientists before. I'm not prepared to discuss it on either of those levels at this point.
I have called tea Chinese Red Bull to compare it to a modern craving for caffeine. But I think their culture has a milder craving than ours.
I am prepared to discuss steeping from the perspective of the best taste as told by our Chinese instructors and students of tea. We have been given a general set of 'quick steep' or 'rapid steep' instructions from a master of Chinese tea. They are designed to get the best flavor out of our premium, whole leaf China teas.
These instructions for proper steeping are the result of thousands of years of Chinese civilization, cultivation, research, observation and meditation.
Our glass steeping beaker holds 8 ounces (235ml) of water. Each tea type and each tea has slightly different 'bests' which adds to the art of making tea but there are some general rules. The more the tea is processed the hotter the water is one general rule. Another rule is that you will get 4-10 steeps per tea weight used.
Our quick method for steeping black tea is to make a quick 5 second rinse of the tea, using just enough water to cover the leaves. The amount of black tea to use is up to 10 grams(which is a lot of tea) but the steeping time is only 15-30 seconds at 205-212 F water. That is the first steeping. It makes a non-astringent, unburnt, properly cooked cup of tea. Time is adjusted to taste and amount of astringency desired for the next 3-6 steepings. A thermometer is used to control and measure for water and brewing vessel temperatures.
Dark oolongs are very similar with slightly lower water temperatures (195-205F).
Green oolongs (6 grams of tea/8 ounces of water) remain without astringency (185-200 F) for a similar length of steeping time. It is not recommended that they be rinsed. What makes a difference is the way a leaf is processed like a tiquanyin which is a tight leaf.
Green teas(6g/8oz) but the temperature will vary (170-195 F) depending upon the size of the leaf(Biluochun low and jasmine dragon pearls/jade fire high). No rinsing was given in the instructions as many of the unique and high note flavors would be lost. Jade fire and other wrapped leaves require a slightly longer (5 seconds) steeping time.
With the preceding being noted on method, a good tea taster can determine exactly when a tea becomes astringent. This happens in a matter of seconds (not minutes) so that a tea becomes over-steeped (unless you prefer bitterness).
I have steeped hundreds of teas this way for the last couple of years. If astringency correlates to caffeine then one can lessen the caffeine in the cup by tasting it and stopping the steep.
If these instructions are followed in China for making tea then much of the tea the Chinese drink has lower caffeine than tea drunk in the west. Your charts and data indicate that the longer the steeping time the more caffeine in the drinking cup.
I agree. For my personal taste now, I cannot steep tea for 1-3 minutes. It gets too bitter for me.
While I was reading your blog I was struck by the idea that the method touted for decaffeinating teas by rinsing for 30 seconds might in fact be the way to have less caffeine per cup.
Your data shows that 9% of the caffeine comes out in the first 30 seconds as the leaf hydrates. If we drink this tea as the Chinese do then we are drinking a 91% caffeine free drink as measured against the total dry leaf caffeine.
I will leave with this conclusion for myself. Less steeping time means less caffeine. If I can get a good cup of tea in 30 seconds with the same amount of tea I will have less caffeine than a tea boiled for 5 minutes.
Thank you for your blog. More later.
Mitchel Noble
PeLi Teas
Is there another way other than the HPLC to measure caffeine.
ReplyDeleteNigel,
ReplyDeleteYou seem to be dismissive towards decaffeinated teas. I believe you said they are indifferent at best. But please understand that some people do have medical conditions and can only drink decaffeinated products. I have epilepsy, and the level of caffeine in decaffeinated tea does not affect me, but the level in regular tea does. I am sure there are others who have valid reasons for drinking only decaffeinated tea.
Thanks,
Tim
So, for those of us that would like no caffeine in our diet, what is the best black team? I purchse decaf now but your article just confused me more than helped!
ReplyDeleteIn reply to "those of us that would like NO caffeine in our diet, what is the best black tea?" - the only cure is abstinence.
ReplyDeleteNo need for confusion - these are the facts:
1. All (Camellia sinensis) teas have caffeine.
2. All decaffeinated teas (be they hot water washed or solvent extracted) have some caffeine remaining.
3. Decaffeination also removes some (amount depending on method) AOXs and flavor compared with the "real thing".
4. If you are caffeine intolerant there are plenty of herbal beverages to choose from.
5. Attempt to make tea into a decaff drink and you will get an inferior product for sure.
6. Some tea vendors, be they unscrupulous or ignorant (you choose) will boost their sales by telling you otherwise.
Nigel at Teacraft
Wow...what a repository of information this article is! I work at Starbucks and have seen this myth in action before. Will gladly spread the word to all those willing to listen (key word = 'willing'.) Had no idea that testing for caffeine was such an expensive business, either. Thanks for sharing, and thanks to all the commenters as well who helped to clarify the information with their questions.
ReplyDeleteThis article is astonishing! More facts than my brain can absorb...but completely fascinating.
ReplyDeleteHowever, I am still a bit confused...mostly by the terminologies. I am, after all, just a simple person.
When you say that steeping tea for longer periods of time "extracts" more caffeine from the tea...where does the caffeine go? Does it evaporate into the air...leaving less of it in the tea water? This point in the steeping process is where I am most confused.
For example: Let's say I put just one teabag of ALREADY decaffeinated green tea into an 8-oz cup of less-than-boiling water. I steep it for two minutes.
At the end of the two minutes, will the tea water in the cup have even less caffeine in it than when I started? AND...would this steeping process apply to three tea bags in a pot of three to four cups of water?
I have a heart condition which can be affected by too much caffeine...so I have been drinking decaffeinated green tea. It perhaps is not the BEST product I could have, but the caffeine level is good for me and I have become accustomed to the taste...which really isn't that bad.
I would appreciate your expert opinions.
JosephT
Perhaps I'm missing the point here but why can't one use the data in reverse to get the same result. By which I mean control caffeine by how long you brew. For example , if you want 80% decafinated simply brew for one minute, no more. Definately tastier than decaf.
ReplyDeleteSo much informations, thanks for that post. I always wondered how it really is with the caffeine in tea.
ReplyDeleteNigel, the FDA do not allow MC tea because of the risk of carcinogenic residues from the solvent being retained on the tea. When asked, "Why then Coffee?" an FDA source stated that the coffee roasting step flashed off these residues. I did bring up the fact that much MC is produced on the green leaf and tea is, through processing, oven dried, enabling any flashing. The FDA were interested but considered the item so far down the priority list that the ban would never be lifted.
ReplyDeleteJohn, you are absolutely right. For "on-line" methylene chloride decaffeination of black tea dhool after oxidation followed by normal firing there is adequate flashing of MC. I have argued (to little effect) the FDA discrepancy between MC decaff coffee and MC decaff tea. When it counted the coffee lobby was strong and the tea lobby weak, and as you point out righting this one is now way down their priority list. Though on-line MC decaff gives a good cup of tea the market preference is now for "natural" caffeine flushing with extreme high pressure supercritical CO2 in complex stainless steel bombs. I have not yet discovered why North Americans are so obsessed with caffeine - though I suspect that undue regard for medical "advice" may be at the root of this.
ReplyDelete"The proof is in the pudding"...
ReplyDeleteHaving had crippling sleeping problems, due to a rare poisoning, I had to honestly examine the effects that my once-so-loved cup of tea might be contributing to that problem. So I just went off all caffeinated tea, with immediate (better sleeping) results. Then I heard about the "quick, 30-sec. decaff trick"and found,once again, I was suffering from those sleepless nights! Again, I went off all "quick decaff" tricks and, what do you know? I have some semblance of a "good night's sleep"once more! So,after having experimented, (knowing nothing about these afore-mentioned studies, with their scientific proofs), I have come to see the validity of there being influential vestiges of caffeine present, even with the "quick trick" (for someone who is hyper-sensitive to any stimulant; i.e., myself).
Hence, "the proof is in the pudding".
The solution is quite simply; abstinence! Like I read in one of the articles; caffeine was part of what God intended tea to have, so I must bow my head to this fact! I can't try to change its composition, and still effect a better night's sleep; "have my cake and eat it, too", but I can eliminate it altogether and KNOW I will be sleeping better! So, there you have it...
The afore-mentioned research has helped to confirm what I had not wanted to face: give it up! Thank you, sirs, for that confirmation! And, "good night"!
:-( I just ordered a bulk (5oz) of organic white tea silver needle! I read that they contain the least caffeine and the most antioxidants! I'm pregnant so I watch my caffeine and now I am so upset knowing this. Nigel can you give me a way to decaffeinating the white tea in hot water wash? How long in minutes to steep it to remove 80% of the caffeine and in what temperature. Also, will hot water wash reduce the antioxidants in the white tea? I don't mind the inferior flavor after the wash as long as I know I keep my caffeine checked. Let me know :) thanks!
ReplyDeleteHi Anonymous, your tea vendor should know better - it is well established now that all teas derived from buds are very high in caffeine - white tea having some of the highest levels of all. If your vendor misinformed you I would advise returning the tea to him for a refund or exchange. As my blog clearly shows there is no quick home based method for decaffeination. Unfortunately all hot water methods will remove the other beneficial compounds (AOX polyphenols and theanine) in equal or larger ratio to the caffeine removed. If you wish to reduce your caffeine intake slightly you need to either make youy tea weaker (less leaf), or switch over to oolong teas (generally lower in caffeine than white teas. BUT if you need to cut out caffeine totally you should switch to caffeine free rooibos herbal tea (this has good AOX profile). Note that even "decaffeinated" teas still contain some caffeine. BTW, congratulations on your pregnancy.
ReplyDeleteThank you so much! I will just keep the white tea for my husband (he drinks a lot of red bull to keep him going on a 12hrs. work day, I am hoping this will substitute it). If not then it would make a nice gift. I will definitely order rooibos herbal tea! Thank you so much Nigel! This particular blog is heaven sent and full of information. Keep it up and blessings!
ReplyDeleteHi Nigel
ReplyDeletewhat an interesting article and responses. I am in a very particular situation. I have found that I am very sensitive to caffeine and a cup of green tea at 4pm has me sleepless at 2 am. Not exaggerating. So years ago I stopped drinking tea and coffee. I now have a pretty severe return of childhood eczema and there appears to be some good evidence from japan that drinking Oolong can be very therapeutic. They tested 1 litre of oolong (35g tea) a day, divided into 3 after meal doses. I want to try it but before I start with just a teaspoonful I thought I would seek some more scholarly advice. I have read all the myths you discuss and now wonder what you would do if you wanted to drink oolong but wanted to minimise caffeine?
Thanks Nigel,
ReplyDeleteSo, would I be right to infer that instead of tipping out the first 30 seconds of steeped tea, just remove the bag and drink that first steep, then in would only be having about 20% of the caffeine?
Kirsty
This is a most interesting article. Thank you Nigel. However, I am still left wondering how much caffeine I am consuming per cup. Most frustrating that I could be drinking another cup per day without harming my unborn child!
ReplyDeleteYou mention two facts, which leave me wondering if they cancel each other out:
1)Indian cafes tend to boil the tea to extract the most caffeine (this explains why they add so much sugar and milk!).
2) Turkish teas tend to be lower in caffeine due to older bushes, more mature leaves, and their drying methods (if I've understood correctly?).
Would I be right in assuming, then, that if I made a jug of Masala Chai, using the method below, there would be a lower level of caffeine in my cup than the average cup of PG tips?
1) Boil the spices for 5 minutes
2) Add the tea leaves and boil for 45 seconds
3) Leave to steep for 1 minute then strain immediately
4) Store in fridge and reheat with milk and sugar to taste
(8 tbsp of tea is used to 6 cup measures of water and my husband claims it tastes weak)
Sorry if this is too specific for you. I wish there was a cheap way of measuring caffeine content too, otherwise we wouldn't all be in this pickle.
Emily
I found on the internet a 2010research paper from Addis Ababa University in Ethiopa that seems to support the findings by the Spiro study. In one part of this study four Ethiopian teas Addis, black lion, cinnamon black and green tea were immersed into 30ml water at 94 degrees c and stirred for 3 minutes. The results were about 65% of the caffine was extracted.
ReplyDeleteAnother finding was that higher temperatures increased the total amount of caffeine removed.
I became interested in removing caffeine from tea when several years ago I was diagnosed with irritable bowel syndrome and told to avoid all caffine forever. After staying off all caffeine for months and trying decaf tea which I did not care for I became 100% better. I read on the internet the 30 minute decaf and tried it with the result of getting sick again. Not willing to give up so easily I went to a minute and a half. To my relief I did fine. I then went to a minute and was still not sufferring any ill. After some trial and error I have been steeping the tea for a little over a minute and doing fine. I find the tea has a lot more flavor than the 97% decaf variety.
In my case I did not need to go to fully decaf tea and maybe others are in the same boat i am. I would really like to see someone do a study at lower steeping times and using different methods of brewing the tea.
I found this article to be one of the best articles on the internet. Thanks much.
Just noticing what Anonymous said. According to Nigels first table I would be better off to steep my tea for only one minute and drink tea that was only 18% of the usual caffine of that tea. Excellent observation! This is one reason I would like to know more. Maybe one day.
ReplyDelete30 seconds: 9% caffeine removal
1 minute: 18% caffeine removal
2 minutes: 34% caffeine removal
3 minutes: 48% caffeine removal
4 minutes: 60% caffeine removal
5 minutes: 69% caffeine removal
10 minutes: 92% caffeine removal
15 minutes: 100% caffeine removal
I know it's generally bad form to comment on a blog post this old, but I found something in a publication in the Journal of Ethnopharmacology that may be relevant to this discussion. This study involved interviewing tea farmers in Yunnan on their perception of the health benefits of tea produced in different seasons and then comparing their responses to chemical analyses of the teas. According to the authors "No correlation was found between informants’ perceptions of stimulant properties and [caffeine content]." So even if you could know that black tea was higher in caffeine than green, that wouldn't necessarily mean that they'd be different enough for you to notice.
ReplyDeleteAhmed S, Unachukwu UJ, Stepp JR, et al (2010) Pu-erh tea tasting in Yunnan, China: Correlation of drinkers’ perceptions to phytochemistry. Journal of Ethnopharmacology 132:176–185. doi: 10.1016/j.jep.2010.08.016
To complicate matters further, I'd like to point out to people that resteep their tea leaves that the caffeine extraction per time will be different than someone that's doing one long extraction for the same amount of time as their multiple extractions, because in between steeps the leaves stay wet and 1) compounds are extracting into the water clinging to the leaves between steeps and 2) the time the leaves are wet but not steeping is still softening the leaves and making it easier for compounds to come out once they're steeped again. I suspect that five one-minute extractions (with a few minutes between each extraction) will extract more caffeine in total that one continuous five minute extraction.
ReplyDeleteAfter reading the article & skimming through all comments as thoroughly as possible, I noticed that no experiments or evidence is given as to (approx.)HOW MUCH CAFFEINE would there be in the SECOND steeping of teabag in clear, hot water?? This WOULD change the parameters would it not? A % of caffeine is already left in first wash,THEN tea (bags/leaves) are resteeped in boiling water 2nd time. Possibly the pH of clear water is different than partially steeped tea & further steeping in new water would change rate or % of extraction. I'm just theorizing 2 clarify my point here, but to me, the whole question of hot water washes & caffeine levels has only been HALF addressed by the experiments & corresponding tables of data. Would be very interested in seeing future test results.
ReplyDelete(November 2015)
ReplyDeleteI tried to find an answer to the ole '30 second extraction' idea a year or two ago and found graphs that, all put together, gave me the impression that most of the caffeine would be in the liquid after 2 - 3 minutes of steeping the tea (loose leaf in a teapot, strained while pouring).
This is my personal experience; I 'feel' the caffeine from that first 2-minute brew from any color tea. If I 're-brew' the same leaves for 3 more minutes I don't 'feel' the caffeine.
But - the first brew of 2 minutes tastes great! Full flavor! Yum.
The second brew has no scent and tastes ... watery, with much less flavor. The only exception I have found is an Oolong tea which adds flavor to the second and possibly the third brews.
I noticed no one mentions how the tea tastes after a short brew compared to using the leaves again...
My solution (no pun intended ;-) is to brew the leaves twice, first for 2 minutes, I enjoy a cup of caffeine-charged tea while brewing the leaves a second time. I then mix all the tea for what I call a 'caffeine-reduced' beverage. That I store in the refrigerator and reheat for my morning cups as long as it lasts. That 'combined' tea never gives me the jitters that the first 2-minute brew does.
My conclusions - A high percentage of the caffeine must be in the liquid after a 2 minute brew. A lot less is in the second brew. The two mixed together gives me a nice balance that my body can handle, and the flavor is nice.
By the way, terrible as it sounds to the tea aficionados (sorry!), I simply use boiling water with all my tea. I don't have time or the technology to figure out the water temperature before pouring it into the pot. I suspect most casual tea drinkers do the same.
And, by what I have read, boiling water probably extracts the caffeine faster than a lower temperature.
I recommend for those folks who can't drink 'any' caffeine to drink herb teas, sorry.
Also, you non-caffeine drinkers, stay away from hot chocolate with real cacao. I learned that from experience.
:-)
Wait a minute. I just read the "Tea Preparation and its Influence on Methylxanthine" study and they only tested the amount of caffeine extracted at the 5, 10 and 15 minute marks. You can NOT simply extrapolate to determine the amounts extracted below the 5 minute mark. Without actually measuring the caffeine extracted at these time points you can not know whether the extraction is linear or logarithmic.
ReplyDeleteThank you Anonymous (6.17PM) for your valid point.
ReplyDeleteSince I wrote this caffeine blog in 2007 some further studies have been made - notably and quite extensively in "Caffeine in Chiang Rai tea infusions: effects of tea variety, type, leaf form, and infusion conditions" by Siripat Suteerapataranon et al. Food Chem. 114, 1355-1338, 2009, which at least shows that the caffeine diffusion (which for I extrapolated between 0 and 5 minutes) follows an inverse logarithmic response, as might be expected, though over the timescale involved has very little real effect on my conclusion that a 30 second steep is not a panacea for home decaffeination.
Nigel at Teacraft
Hi Anonymous(6.17PM). Since I wrote this caffeine blog in 2008 more studies have appeared - notably and most extensively "Caffeine in Chiang Rai tea infusions: effects of tea varaiety, type, leaf form, and infusion conditions" by Siripat Suteerapataranon et al. Food Chem. 114, 1335-1338, 2009. This clearly shows an inverse logarithmic relationship between 0 and 5 minutes where I had use a straight line interpolation. In the event it has very little effect on my conclusion that a 30 second steep cannot in any way be heralded as a panacea for home decaffeinators.
ReplyDeleteNigel at Teacraft
Hi Anonymous(6.17PM). Since I wrote this caffeine blog in 2008 more studies have appeared - notably and most extensively "Caffeine in Chiang Rai tea infusions: effects of tea varaiety, type, leaf form, and infusion conditions" by Siripat Suteerapataranon et al. Food Chem. 114, 1335-1338, 2009. This clearly shows an inverse logarithmic relationship between 0 and 5 minutes where I had use a straight line interpolation. In the event it has very little effect on my conclusion that a 30 second steep cannot in any way be heralded as a panacea for home decaffeinators.
ReplyDeleteNigel at Teacraft
Hi Anonymous(6.17PM). Since I wrote this caffeine blog in 2008 more studies have appeared - notably and most extensively "Caffeine in Chiang Rai tea infusions: effects of tea varaiety, type, leaf form, and infusion conditions" by Siripat Suteerapataranon et al. Food Chem. 114, 1335-1338, 2009. This clearly shows an inverse logarithmic relationship between 0 and 5 minutes where I had use a straight line interpolation. In the event it has very little effect on my conclusion that a 30 second steep cannot in any way be heralded as a panacea for home decaffeinators.
ReplyDeleteNigel at Teacraft
Surely you must mean "metallic" stirrer in the description of the first experiment, not "magnetic" stirrer. Although introducing a magnet into the mix might be interesting...
ReplyDeleteA magnetic stirrer is a standard piece of laboratory equipment that allows a glass vessel of liquid to be stirred by a small plastic coated magnetic rod in the liqid (termed a flea) which is magnetically attracted by a rotating magnet in the heating plate on which the glass vessel stands. I remember them being introduced in the 1960s - they saved a lot of time-consuming manual stirring with a glass or metallic stirrer.
ReplyDeleteNigel at Teacraft
Given that the articles referred to show a slower extraction of caffeine, this also means that a high proportion of caffeine is left unextracted by the tea drinker. I aren't many tea lovers that steep tea more than 5 minutes. It would be interesting to measure caffeine extraction when loose leaves are steeped multiple times. When steeping tea for a long time, the water cools off, while with flash brewing each round comes with fresh hot water.
ReplyDeleteHas the author answered the above question (using the data in reverse): If you brew tea for 1 minute only, would you achieve about 80% caffeine removal?
ReplyDeleteCaffeine is very soluble. Using cold water to decaffeinate tea for five or ten minutes should be a matter of interest, as it may would not remove a lot of the flavoring from the tea. Anyway, this is what I do if I want tea before bedtime and it seems to work. I know this is anecdote and not science.
ReplyDeleteThanks for this complet and deep article. It is always nice to find information based on experiments and not believes. Is difficult to find information on internet about this topic based in results. Thnaks for that!
ReplyDeleteRon, Caffeine is very sparsely soluble in cold water (2.17 g/100 ml @ 25 deg ) whereas solubility is 20.0g/100ml @ 80 deg C and 66.6g/100m,l at 100 deg C I don't believe a 5 or 10 minute soak in cold water would markedly affect the caffeine content of the remaining leaves.
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