Thursday, May 18, 2017

Making your tea less bitter

In the Wednesday post, I mentioned that as the ratio of amino acids to polyphenols in oolongs increases, the value of the tea increases, and suggested that the reason is that polyphenols are bitter, so potentially aversive, while most of the amino acids in tea are sweet and savory (umami), giving the tea a delicious flavor.

The question is then, how can you make a lower grade oolong taste more delicious?

One way, as I will explain in my talk about cold versus hot brewed tea at World Tea Expo 2017* is to brew the tea cold, because much less polyphenol gets into the cup.

The other way is to inhibit the bitter message, which can be done with a tiny amount of salt. We will try this experiment in my other session at World Tea Expo, a focussed tasting called "Pairing with Tea: the Science of Flavors and How to Enjoy Them!" Wednesday  June 14th. Here is a diagram of taste bud cells you may have seen on this blog before:



The X from the salt-sensing cell to the bitter-sensing cell indicates inhibition. There is an X from the sweet-sensing cell to the bitter sensing cell as well, but you need relatively more sweet than salt to sense the effect.

Hope we will be to carry out this and other experiments together at WTE!


* What's in the Cup & Why You Like It: Hot Brewed vs Cold Brewed - CS49
Tuesday, 06/13/2017: 8:30 am - 10:00 am
Room: N237
Session Number:  CS49

Wednesday, May 17, 2017

Oolong quality and amino acid/polyphenol ratio

One of my two talks at World Tea Expo 2017 will be on cold- versus hot-brewed teas.* (The other will be about pairing with teas, about which more in my next post.)

One of the most important conclusions we will reach is that the quality of a tea depends on the ratio of amino acids to polyphenols. Here is a result from a paper on oolongs: the more prized the oolongs — and the more costly — the higher the ratio.**



Looking forward to seeing you at WTE 2017! 


* What's in the Cup & Why You Like It: Hot Brewed vs Cold Brewed - CS49
Tuesday, 06/13/2017: 8:30 am - 10:00 am
Room: N237
Session Number:  CS49

** Yueh-Tzu Hung, Po-Chung Chen, Richie L.C. Chen, Tzong-Jih Cheng. Sequential determination of tannin and total amino acid contents in tea for taste assessment by a fluorescent flow-injection analytical system. Food Chemistry 118 (2010) 876–881.

Thursday, April 27, 2017

How much theanine in your cup?

When I was looking for information to share with you all at World Tea Expo come June, found a fascinating paper about L-theanine content of different teas available in England. L-theanine is a compound found in young tea leaves that may (or may not) have worthwhile effects on your mood and sleep.*

You may have heard that green tea has more L-theanine than does black tea. However, as the authors indicate, the studies providing these measures extracted total theanine from the leaf—they didn't measure the amount of L-theanine that gets into the cup you actually drink.

That's why the authors of the paper measured extracted L-theanine, namely the amount in a cup of 200ml, with the tea brewed with water at 80ºC for 2 minutes.

Under these circumstances the results were reversed, as the graph below shows. For the sake of simplicity, all of the teas I included in the graph were Twinings teas—several other brands of teas were tested, with the same results. 

Average theanine content of different Twining's teas.


The "Everyday" tea was a bag tea, while all the rest were loose leaf. The first difference is that the loose leaf teas released significantly less theanine than the bagged tea. The second difference is that the green and white teas released less than some, but not all, of the Twinings black teas. 

When all of the teas tested (including teas produced by other companies) were taken together, however, black bagged teas released significantly more theanine than did the loose leaf black teas and the loose leaf green and white teas. It is likely that the leaf particles in bagged teas offer more surface area to the water for extraction. With respect to the difference between some black teas and other teas, the difference may come from the more extensive processing of black teas, which may release more theanine.

Incidentally, for most of these teas, the maximum theanine was released at 2 minutes of brewing; and lemon, sugar, or small amounts of milk had no effect on theanine release.

Bottom line: enjoy your specialty loose leaf teas for their exquisite flavor, but if you just need a theanine "hit," go for a bagged tea!


* Emma K. Keenan, Mike D.A. Finnie, Paul S. Jones, Peter J. Rogers, Caroline M. Priestley. How much theanine in a cup of tea? Effects of tea type and method of preparation. Food Chemistry 125 (2011) 588–594.
 
 


Wednesday, April 19, 2017

Mango green tea and dirty socks

The other day, friend of Pairteas and tea connoisseur Marzi Pecen (www.pecen.net) asked me why her mango-flavored green tea had a smell of dirty socks, and why she couldn't taste the mango at all. Here's the (longish) answer — it has to do with the odorants in dried mango and how they interact with those in green tea.

First, what is the difference in odor profile between fresh and dried mango? 

Mango is highly perishable when fresh. By contrast dried mango is quite stable, and can readily be added to tea to create a flavorful blend. 

When I smell or taste dried mango by itself, I get a two step effect. The first effect is cool and slightly lemony, then a warm orange-like tropical fruit aspect quickly kicks in.

This two step effect can be explained from the data obtained by Bonneau and her colleagues, in which they compared fresh and dried versions of the most commonly cultivated mango, Mangifera indica L. cv. Kent.*

Fresh and dried mangoes differ dramatically in their aroma chemistry, though two compounds present in both fresh and dried mangoes — β-myrcene and 3-methylbutyl butanoate — together contribute strongly to the "mango" sensation.  Both of these compounds activate warm receptors.

The lemony sensation from dried mangoes comes from the presence of limonene and a small number of other terpenes with a citrusy flavor. Limonene in particular activates the cold receptor, which is why the first fleeting sensation is cool — cool receptors turn on quickly and turn off quickly, especially when turned off through activation of warm receptors, including sweet receptors. 

That's why the sensations quickly becomes warm: the "mango" compounds start activating the slow-responding warm receptors, and the flavor becomes intensely mango-y.

Next, what happens when you add dried mango to green tea?

Here's where we run into flavor problems! The process of drying mangoes leads to the production of hexanal and heptanal, and the disappearance of mesifuran. Hexanal and heptanal both activate the cool/cold receptors, while mesifuran is a major contributor to the sweetness and warm flavor of fresh mangoes. 

When dried mango is added to green tea (which itself activates cool/cold receptors) the balance of flavors shifts from warm to cool/cold. As a consequence, the major mango flavor compounds — β-myrcene and 3-methylbutyl butanoate — cannot be sensed => no mango flavor!

At the same time, the cool/cold activating aromas are exaggerated...and heptanal has a smell of dirty socks...

The following chart shows the relative odor activity values (OAVs) of these compounds in fresh and dried mango, according to the data from Bonneau et al.:


Odor activity values of selected compounds in fresh and dried mangoes. Data from Bonneau and her colleagues.*



As you can see, drying increases the OAVs of the two characteristic mango compounds, and completely eliminates mesifuran. The cool/cold-receptor-activating limonene increases slightly, while hexanal and heptanal make an appearance, so heptanal can offer its dirty odor.

Just thinking it would be very interesting to contrast mango-infused green tea with a mango-infused oolong. My guess is that the mango-ness would be enhanced and the dirty-sock effect diminished when you pair dried mango with a warm receptor activating oolong such as Tie Guan Yin. Give it a try?


* Bonneau, A., Boulanger, R., Lebrun, M., Maraval, I. and Gunata, Z. (2016), Aroma compounds in fresh and dried mango fruit (Mangifera indica L. cv. Kent): impact of drying on volatile composition. Int J Food Sci Technol, 51: 789–800. doi:10.1111/ijfs.13038

Saturday, April 15, 2017

Why do tea and books go so well together?

A fascinating article in The Guardian, based on research presented by Cecilia Bembibre and Matija Strlič,* may well have given the answer...

https://www.theguardian.com/books/2017/apr/07/the-smell-of-old-books-science-libraries

As you may know I have been hard at work clearing out my home of nearly thirty years (anniversary in August) in preparation for moving to be near my daughters and grandchildren. One of the difficult tasks has been to triage my many thousand volumes, each of which holds a special message for me -- books I read as a child, books that once belonged to my grandparents and even greatgrandparents, medical books, science books, math books, history books, school books, and especially books that my children loved to look at as toddlers and from which my parents and I read to them...

So I have been surrounded by that rich old book smell, and memories of curling up with a good book, cup of tea at hand, immersed another world.

Turns out that old book smell is made up of a number of compounds that are also contained in tea. The Historic Book Odor Wheel from the article (below) was created to show the different characteristic odors of an historic book and to indicate the corresponding compounds the authors were able to identify. I added red stars for compounds that are also present in tea, and a yellow arrow for limonene, which is present in bergamot and therefore in Earl Grey tea.



As you can appreciate, pleasant odors in the historic book are also present in tea, particularly in black tea (furfural and benzaldehyde). The "-al's" — hexanal, heptanal, and to a variable extent undecanal, are more characteristic of green teas, where they contribute to the grassy green flavors; and benzaldehyde is found in oolongs, too.

As I think about it, it's the lack of book smell that explains why I can't curl up with a good computer or Kindle.

* Cecilia Bembibre and Matija Strlič. Smell of heritage: a framework for the identification, analysis and archival of historic odours. Heritage Science20175:2
DOI: 10.1186/s40494-016-0114-1.
By the way, this article is open source so you can go on line to read it in its entirety, an exciting and worthwhile exercise because of the elegant discussion of smell as heritage:
https://heritagesciencejournal.springeropen.com/articles/10.1186/s40494-016-0114-1

Wednesday, March 15, 2017

Tea and Teeth

Sorry I haven’t posted here in a while…as you may know from my Facebook postings at facebook.com/pairteas, I have just published my book “Three Basic Teas & How to Enjoy Them.” You can get it on createspace or look for it on Amazon.



...and I am in the process of down-sizing, selling my home of nearly 30 years, and moving into a much tinier apartment—so much sorting and choosing what to keep and what to sell and what to give away. So far several hundred books made their way to our local Friends of the Library Book Sale that supports our local library system.

...and yes, I did get a storage unit because there are things I simply can’t part with as yet…saving that step for another time in the hope that my children will want some of it someday.

But I have been reading…and came across an article about teeth blackening by Thomas J. Zumbroich “To Strengthen the Teeth and Harden the Gums - Teeth blackening as medical practice in Asia, Micronesia and Melanesia.” *

This article brought back memories** of reading years ago about black teeth among the Japanese, which was achieved by soaking iron nails in vinegar, then adding green tea powder and coloring the teeth with that mixture at least every few days. The result was the black teeth we see in pre-Meiji era Japanese prints, but also teeth that were far healthier than ours today. The green tea offered fluoride and the iron strengthened the enamel, and together they prevented gum disease, possibly through antibacterial compounds in the tea. 

Geisha blackening her teeth at 1AM, by Tsukioka Yoshitoshi,
number 13 of the series "24 hours in Shinbashi and Yanagibashi."

In shogunate Japan black teeth were considered beautiful and a sign of a woman's sexual maturity, but the opening of Japan to the world and the influx of Western ideas and ideals changed all that in the Meiji era. When a law forbidding the practice was promulgated in 1870,  and  the Empress appeared with white teeth in 1873, teeth blackening died out almost completely. White teeth and the accompanying tooth decay set in.



** In “Medical Botany” by Memory Elvin-Lewis (yes, that’s her name and the pun above was intended). The current edition of this work is Lewis W, Elvin-Lewis MP. (2003) Medical botany: Plants affecting human health. 2nd ed. New York: John Wiley Interscience; 812p. BTW, Professor Elvin-Lewis is at my alma mater Washington University, another reason for me to appreciate her delightfully anecdote-rich encyclopedic work.


Thursday, February 9, 2017

The calmness of sugar

Was reading an article about the effects of drinking tea with sugar versus tea with stevia, tea with sucralose (sold here in the US as Splenda, for example), and tea without sweetener, on stress reactions.* 

Fifty people of a wide range of ages participated in the experiment. On the test days the participants first filled out a questionnaire about their level of stress, then after either the no-stress or the stress condition drank teas. In the no-stress situation, participants simply filled out a questionnaire about their mood state; in  the stress situation they had 10 minutes in which to solve math and logic problems, which they were told was going to tell the researchers whether they had high, medium, or low IQ.  This test has been shown to reliably induce stress (no surprise there!)

Here is the tea-drinking methodology as described in the article:
“Participants were then seated in individual sensory booths to taste the tea samples. A total of four samples were presented in a sequential monadic fashion based on William Latin Square Design31. Approximately 90-mL of each sample was provided in a 112-mL cup with a three-digit code. Participants were asked to rate on a 9-point scale how calm (1: extremely stressed; 9: extremely calm) and pleasant (1: extremely unpleasant; 9: extremely pleasant) they felt before drinking the tea samples. Participants were then asked to drink the entire cup of tea and rate only its sweetness intensity on a 15-cm anchored line scale (0: extremely weak; 15: extremely strong). Participants also rated their overall liking of the tea sample on a 9-point hedonic scale (1: dislike extremely; 9: like extremely). Participants also rated how calm and pleasant they felt after drinking the tea sample similar to how they did before drinking the sample.
The order in which they drank the teas varied from person to person. From reading the methodology, the authors did not take into account this order in the data analysis. I assume that they felt they didn’t need to do so, because they felt that the results clearly favored the calming effect of tea with sugar compared to tea with the other sweeteners. Here is the graph:


[BTW, wondering why the calmness was negative for both stevia and unsweetened, rather than neutral...no explanation for this in the paper, and of course we don't have any idea about the order of presentation of the teas and whether this order may have led to any outliers, not to mention whether there were people who were utters to begin with.]

The authors speculate that the reason that the sugar was more calming was because it provided the brain with the calories it needed to deal with the stress. As they noted, the brain needs glucose to function—in fact it uses more glucose than any other organ of the body, and takes up about 3% of the calories we need each day. 

At the same time, they point to literature that suggests that sucrose activates many more brain pathways than do artificial sweeteners.** Therefore another possible explanation for the effect may be that the reward circuits in the brain are activated more readily by sucrose than by other sweeteners.

I would like to point to another possibility: that theanine and caffeine in tea crosses the blood-brain barrier and enters the brain more quickly and easily in the presence of sucrose. Theanine has a calming effect that is pretty well established, at least when taken by itself. When taken with caffeine, it may be even more effective.*** (See my blogpost http://virginiaspairteas.blogspot.com/2016/01/caffeine-l-theanine-and-egcg-and-timing.html).

When sugar is added, caffeine and theanine may go into effect more quickly. Here’s why:

There is a transport system for neutral amino acids into the brain that works when the system can also transport glucose (sucrose is made up of two molecules of glucose). Caffeine also enters the brain more easily with a dollop of sucrose. In this study, theanine and caffeine entered the participants’ bloodstreams throughout the tea drinking process, no matter what sweetener was. But when sucrose was available, theanine and caffeine could zip right into the brain. The result would be a and focussing  effect!

You can try this experiment for yourself. Assign yourself something somewhat stressful to do — for me it was writing this blogpost. Then use either a sweetener or sucrose and see what the effect is. Repeat on some other occasion, with the other compound—if you started with the sweetener then sucrose, or vice versa. And let me know what happened.

For me the sucrose was indeed more effective…

But here is a catch: if you use artificial sweeteners regularly (I don’t), your brain will light up the reward circuits in the same way as sucrose…and maybe act as if you had taken sucrose with your theanine and caffeine.****

Let me know what results you get with the experiment I suggest, and when you do, let me know whether you take artificial sweeteners regularly.


* Samant, S. S. et al. Tea-induced calmness: Sugar-sweetened tea calms consumers exposed to acute stressor. Sci. Rep. 6, 36537; doi: 10.1038/srep36537 (2016).

** Guido K.W. Frank, Tyson A. Oberndorfer, Alan N. Simmons, Martin P. Paulus, Julie L. Fudge, Tony T. Yang, Walter H. Kaye. Sucrose activates human taste pathways differently from artificial sweetener. NeuroImage, Volume 39, Issue 4, 15 February 2008, Pages 1559–1569.

*** Camfield, David A; Stough, Con; Farrimond, Jonathon; Scholey, Andrew B. Acute effects of tea constituents L-theanine, caffeine, and epigallocatechin gallate on cognitive function and mood: a systematic review and meta-analysis. Nutrition ReviewsISSN 0029-6643, 08/2014, Volume 72, Issue 8, pp. 507 - 522

**** Erin Green, Claire Murphy. Altered processing of sweet taste in the brain of diet soda drinkers. Physiology & Behavior, Volume 107, Issue 4, 5 November 2012, Pages 560–567

As an aside: remember Jolt, the cola drink “with all the sugar and twice the caffeine?” One afternoon many years ago was working on a project with a student when we both started to flag, and thinking had become absurdly difficult. I then remembered that another student had given me a bottle of Jolt, so I unearthed it and we each took a swig. About 10 minutes later we both looked up…the Jolt had jolted us! The caffeine was mainlined into our brains by the sugar, and we could finish the job. 

That said, I am not recommending Jolt, just present this story to illustrate how sugar can make caffeine move more quickly into the brain.