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.






Thursday, January 26, 2017

Beer Flavor Map!

The day before yesterday, at the last minute, I offered to give a class on the sensory perception of beer for my friend Scott Kerkmans, Instructor and Director of the Brewing Industry Operations Program at Metropolitan State University in Denver, Colorado (https://msudenver.edu/beer/faculty/). 

Two things fascinated me about teaching the class. 

The first was the opportunity to use Skype to bring me into a classroom 1700 miles away from home. I could run the Keynote presentation (that’s Mac’s Powerpoint) from my computer, and make comments on each slide as I presented them. I could hear the class as I did this, so I could answer questions and respond to their thoughts. It wasn’t as good as carrying out a class in person, where I can see the students’ reactions and clarify my statements as needed, but it worked! So you may see me doing this even more in the future…

The second was that, for the presentation, I looked into the question of the different flavors of beer, and how they engage the trigeminal system. This question led me to the Beer Flavor Map created in 2016 by Lindsay Barr, MS and Nicole Garneau, PhD to supersede the existing beer flavor wheels. Here they are holding up the map and celebrating its creation, from their twitter page (https://twitter.com/beerflavormap): 




The purpose of this map is to give people into beer a vocabulary to describe their experiences. This standardization of vocabulary was the purpose of the original flavor wheel, made by Ann C. Noble at UC Davis for wine. 

As with the wine wheel, I had to keep reminding myself that the Beer Flavor Map is not based on the biology underlying our ability to sense these flavors, but rather on an attempt to put similar flavors together and to give them names relating them to other flavors, for example “wheat” or “lemon.”

Yet what makes this map important, and different from all other maps and wheels that I have seen, is the inclusion of “mouthfeel” as a separate “place” (to continue the map analogy). By mouthfeel the mapmakers mean trigeminal sensations. Here is the “Mouthfeel” section of the map:




“Irritation” and “Afterfeel” are both functions of the temperature (TRP) receptors on the trigeminal nerve. “Effervescence” is primarily a function of the touch receptors on the nerve, though the relationship of “Effervescence” to “Carbonation” brings the temperature receptors into play as well—carbonation activates TRPV1, the “hot” receptors (note “Burning” under carbonation). “Body” is also a function of the touch receptors, but there can be confusion with the “Afterfeel” characteristics, which are a function of TRPV1, at least with respect to astringency and slipperiness.

So exciting to find a diagram for flavor descriptors that acknowledges the contribution of the trigeminal nerve to the overall flavor experience!




Wednesday, January 4, 2017

Amphithermic and freshly ground pepper

Coining a new term: amphithermic, to denote a food or beverage that activates both hot and cold receptors. 

Have been wondering for a while what I should call this phenomenon, when I had a discussion about pepper with friend of Pairteas Marzi Pecen, who pointed out to me that freshly ground black pepper can enhance the flavor of vanilla ice cream.

How can that be?

To answer this question, I first needed to look at the chemistry of peppercorns for freshly ground black pepper. Peppercorns are the dried unripe fruit of a vine called Piper nigrum. To prepare them, the fruits, called drupes, are cooked in hot water for a short while, then dried. The cooking process is short enough that cells walls are broken down, but enzymes are for the most part left intact and freed to act on the cell’s components to create an amazing array of aromatic components. The drupes are then dried, giving a shriveled wrinkled peppercorn.

Peppercorns, from Wikipedia


The seed inside the peppercorn contains the sharp “hot” piperine. White pepper is made from this seed. This is the pepper in shakers that I know from childhood, before freshly ground pepper was commonly available here in the US. I found it disagreeably hot and irritating, and I hated it. Still do! Oh, and it turns out that it contains indole as well. Indole is a stinky chemical that helps perfume when combined with pleasant floral aromas, but without floral compounds is pretty bad (fecal…).

Then, when I was older, I discovered freshly ground peppercorns—what a revelation! While the seed has most of the piperine, the dried flesh of the fruit has an altogether different quality. Its flavor is dominated by cool/cold receptor activating terpenes, such as limonene and pinene, and especially linalool. 

(Do these compounds sound familiar? Yes—you find them in tea!) 

And there’s one more chemical, rotundone, which is also found in herbs that activate the warm receptors, such as rosemary and basil. For you wine drinkers out there: it’s also in Syrah/Shiraz wines, and some other red wines as well, where it provides the peppery aroma.*

(Interestingly, about 20% of people can’t smell rotundone—so if people tell you a Shiraz or Côtes du Rhone has a peppery aroma and you don’t know what they are talking about, you may be in that 20%.)

(Another aside: all of these compounds are highly volatile, so disappear over time. Buy your peppercorns fresh and keep them away from sunlight and in an airtight container. Clear plastic pepper mills filled to the gills with peppercorns are not the answer for the best pepper.)

Back to amphithermic and why freshly ground black pepper might enhance the flavor of vanilla ice cream, and I might add, strawberries. Vanilla activates primarily the warm receptors, and an important flavor compound in strawberries, furaneol, does as well. What I think happens is that, in freshly ground black pepper, the activators of the cool/cold receptor activators and those of the hot ones cancel each other out, leaving the flavors that activate warm receptors, which then have a chance to shine.

If you add lemon to pepper, then the flavor shift is towards the cool/cold receptors, and if you put pepper on a steak the shift will be to the more roasty flavors, and also the warm meaty umami flavors. That’s what I mean when I say that freshly ground black pepper is amphithermic.

Now for an experiment. Don’t have any vanilla ice cream to carry it out, but do have some oolong—oolongs activate the warm receptors. What would adding some pepper to an oolong do?

I have a stuffy nose today, so not the best experimental conditions, but perhaps the pepper could overcome the aroma block? 

It did! The oolong tasted definitely more aromatic and, to put it simply, richer. At the same time I did sense the catch in the back of my throat that pepper gives, so I’m not totally sure that is the best thing to do with a beautiful oolong. Still, gives me some cuisine ideas. 

Any thoughts?


* Wood C, Siebert TE, Parker M, Capone DL, Elsey GM, Pollnitz AP, Eggers M, Meier M, Vössing T, Widder S, Krammer G, Sefton MA, Herderich MJ. From wine to pepper: rotundone, an obscure sesquiterpene, is a potent spicy aroma compound. J Agric Food Chem. 2008 May 28;56(10):3738-44. doi: 10.1021/jf800183k.


Wednesday, December 28, 2016

TEA = CHAMPAGNE?

[Note: this post is an edited repeat of a Pairteas Facebook post from the past—hope you enjoy it, and hope you and yours experience fulfillment and happiness throughout 2017 and beyond!]

...Of course not exactly! 
But for those of us who, like me, can't tolerate alcohol and are thus tea-totalers, is there a tasty tea-based alternative?

Think I may have found it—try it and let me know what you think!


• Started with the question: what is the flavor profile of champagne? According to winefolly.com, champagne has flavors of citrus fruits, white peach, white cherry, almond, and toast (yeasty).
• In addition it has (of course) alcohol, which comes across on the palate as "acid." How to get a similar profile?
• Amazingly, by using white tea: white tea actually has a number of chemicals it shares with peach, cherry, almond, and bready flavors, the latter thanks to its long withering. In addition, it has about half the catechins of green tea, so is decidedly less bitter.
• Next, we need the carbonation. At first was thinking about getting a sparkling alcohol-free apple cider—there are a couple of chemicals in white tea with an apple-like flavor—but champagne isn't apple-y to me, so I nixed that idea.
• So I took myself to our local gourmet store to find a fizzy drink that wouldn't be too sweet, and found Juniper Berry DRY. To find out more about this exquisite sparkling soda, which you can get on Amazon, go to: http://www.drysparkling.com/flavors/juniper-berry/
• Remembering that champagne also has a peach aspect, and that I wanted to cut sweetness a bit (and also because white tea has about half the catechins of green tea), I also got some Fee Brothers peach bitters (http://www.feebrothers.com/products/bitters/peach_bitters.php).

Here's the recipe:
• Bring 18 oz (half liter) of water to 170ºF (I checked with a food thermometer, but you can guess the temp because little bubbles start to appear). Add the water to 8 grams of white tea, brew for 60 seconds, and remove the leaves. This yields a rather dark tea (see photo below), but it will soon be diluted!


• Either let the tea cool down or be sure to put a metal spoon in your glass, then pour equal amounts of tea (first) and sparkling soda (second).
• For each 4 ounces of the tea/soda combo, add two dashes of peach bitters (or more, to taste). 
• Enjoy!!

=>> While you can still taste the tea very gently, the overall flavor and aftertaste is remarkably like champagne, and it feels so very festive!!! 

The picture below shows the result. Note that the tea soaked up some two ounces of the starting water! Sorry it's not in a champagne glass—am in down-sizing mode, and can't reach them right now!




Oh, and the bubbles don't show up in the picture, but the tiny bubbles are there...