Feeling the heat: TRPV1, receptor for hot, capsaicin, and also salt and ethanol!

You probably know about sensitivity to the bitterness of PTC (phenylthiocarbamide) and PROP (6-n-propylthiouracil), and how your sensitivity is genetically programmed. You may even have tried the paper coated with PTC in class in middle or high school. 

Other taste sensitivities are genetically determined as well. As someone who is very sensitive to the burn of chili peppers, I was interested in the genetics of TRPV1, the receptor that causes the burn sensation.

This sensation is created by the binding of the capsaicin in chili peppers to TRPV1, the "hot" receptor. This receptor is designed to respond to temperatures in excess of about 100ºF (40ºC). TRPV1 has numerous genetic variants, which lead to greater or lesser sensitivity, not just to capsaicin, but also to a number of other food components. Here are two examples:

Salt: while a very different receptor in taste buds responds to low salt concentrations, TRPV1 responds to high concentrations with a slight to not-so-slight burning feeling — that's why salt goes so well with caramel. Both caramel and salt at high concentration activates TRPV1, and thereby turns up the volume on caramel flavor perception.

If salt at higher concentrations starts to burn for you it is probably because you have a gain-of-function mutation in your TRPV1 gene that increases salt's ability to activate TRPV1. The original form of the gene leads to moderate sensitivity, while the mutated form leads to greater sensitivity to salt. If you inherit this mutated form from each of your parents, as I did, you are really really sensitive to the "burn" of salt!*

A "burning" heart for Valentine's Day!

Ethanol: Does ethanol (alcohol) burn as it goes down your throat? This burn, too, is due to activation of TRPV1.  Some people experience more of the burn than others, again due to mutations in TRPV1.** In at least one case, the mutation is gain-of-function. This one is a rare mutation, different from the salt burn mutation. I happen to have inherited this mutation from both my parents as well, one of the many reasons I don't tolerate a cabernet sauvignon at 16% alcohol, or even one at 14% alcohol...


* Dias AG, Rousseau D, Duizer L, Cockburn M, Chiu W, Nielsen D, El-Sohemy A. Genetic variation in putative salt taste receptors and salt taste perception in humans. Chem Senses. 2013 Feb;38(2):137-45. doi: 10.1093/chemse/bjs090. Epub 2012 Nov 1.

** Allen AL, McGeary JE, Hayes JE. Polymorphisms in TRPV1 and TAS2Rs associate with sensations from sampled ethanol. Alcohol Clin Exp Res. 2014 Oct;38(10):2550-60. doi: 10.1111/acer.12527. Epub 2014 Sep 25.

Are chefs more sensitive tasters?

The other day a friend  of mine asked whether chefs were more sensitive to flavors than other people. While I don't have a direct answer to this question, I can tell you what my students and I found among chefs attending the National Restaurant Association meetings in Chicago several years back.

We chose the National Restaurant Association meetings because the attendees work in all aspects of the food service business, from chefs to line cooks, to dietitians to restaurant managers, to people selling food and equipment to restaurateurs, to all other food service-related people.

The meetings were (and still are) held in Chicago because the McCormick Center is the one venue that can accommodate the more than 6 miles of booths. As you can easily imagine, walking past all those booths can be pretty tiring, so a booth that offered a seat was enticing! Our booth had several seats.

In exchange for the opportunity to rest their feet, we asked participants to fill out a questionnaire and to carry out a taste test using a LifeSaver(TM) mint. In the questionnaire we asked (among many other things) what the participants did for a living. The taste test involved rating the intensity of the mint flavor and of its cooling effect.

We were fascinated to observe that chefs and cooks got a much stronger cooling effect from the mint than did people who worked the front of the house, or other people in the food service industry, except perhaps sales people. It was this observation that started me on the road to looking at the trigeminal aspect of flavor more deeply.

It is becoming clear that trigeminal nerve function is critical to experiencing flavors. As I mentioned in one of my Facebook posts, the trigeminal response acts like a volume dial, turning up or down the ability to sense flavors. I'll be blogging about this question in greater detail in the coming weeks, so stay tuned!

Here I am with my two students, Nneka Ole Chukwueke and Kalisa Marie Martin at our booth at the 2007 NRA meeting. Participants stuck a star on the board behind us after they completed the questionnaire and taste test. The board said "Help Us Reach 300!"...we went over 360 participants! 

People were intrigued by the brain model, another reason they stopped at our booth. We used the model to explain how flavor is assembled in the brain.

TEA & CHOCOLATE PART 3: POUCHONG

POUCHONG...one of the teas Donna Fellman and I are going to highlight at World Tea Expo...

When I first had pouchong, didn't think much of it...very little flavor...but now as I sit writing this, bending over an aromatic cup, I've changed my mind. 
Brewed it at 190ºF for two minutes. When the tea first hit the water, the most flowery aroma emanated, which quickly turned more toasty. On sipping it was smooth,elegantly flowery with a tiny bit of bite at the back of the throat. Just wanted to drink it by itself, never mind the chocolate! 
This flavor profile is not surprising, as pouchong lies between green tea and oolong in its preparation. What does this chameleon-like quality mean for pairing with chocolate? 
=>> What it means is that it is perfect for pairing!! Only one of the four chocolates I tried didn't do anything for the tea or chocolate.
• That was the Vosges Super Dark Coconut Ash & Banana. All flavors, both of tea and of chocolate, disappeared in the clash of receptors. Pouchong activates cold, warm, and hot receptors, as does this chocolate, so they all negate each other.
• By contrast, with the Chocolove Ginger Crystallized in Dark Chocolate, the ginger brought out the cool grassy melony flavors of the tea coupled with the rich coolness of the ginger, and allowed for the tiny but oh so pleasant bite at the back of the throat. So delectable!
• Ghirardelli 100% cacao? Oh my, a totally different experience! Bitter bitter bitter, more bitter than the chocolate by itself, but ever so deliciously so as the hot receptors kicked in, allowing another flower profile to emerge, this time jasmine. The chocolate turned off the cool/cold receptors, allowing the warm receptors that respond to methyl jasmonate and jasmine lactone, so characteristic of pouchong, to take over.
• Even white chocolate was pretty good with this pouchong. As I said in the previous post, white chocolate is much too sweet for me, but the bitterness of this tea cut the sweetness just enough to make it tolerable, and I could taste the vanilla of the chocolate. Like the jasmine-related compounds in the tea, vanilla activates warm receptors, enhancing the flavor of the tea. Note that the cocoa butter in the white chocolate turns off the hot receptors, so that you are left with activation of warm receptors, with neither bitterness nor sweetness, as a consequence of which the pairing was somewhat unidimensional. 
• Worth noting: this pouchong doesn't taste bitter by itself, but the bitterness can be brought out by activating the bitter receptors with another bitter compound, while its content of catechins is sufficient to tune down sweetness in a pairing.
=>> Dilemma: do I prefer the tea with the ginger chocolate or with the 100% cacao? Drank it all up trying to decide!
Picture above shows the loose tea (can you see the silver needles of the buds? Abundant in this tea!) and the appearance of the tea after brewing. On the upper right I've included a special cup for fragrant tea, made by friend Peter Ting's company 1660 London, to show you what I think is the perfect cup for such a fragrant tea. Reminds me of the aroma collector glasses for Pinot Noir wines. For more about these cups go to: http://www.1660london.com. And here's Peter himself, from his website http://www.peterting.com.

TEA & CHOCOLATE PART 2: PAN-FIRED CHINESE GREEN TEA

Pan-fired Chinese green tea, steeped at 175ºF for 2 minutes, all the same chocolates as the previous post, and this time THE WINNER IS...

Chocolove Ginger Crystallized in Dark Chocolate!!!
• The Ginger and (not so very) Dark Chocolate enhanced both the tea and the chocolate — each was transformed, so I didn't taste them separately, but rather as some magical blend, full of delicate flower and spice. Such a pleasure! And such a contrast with yesterday, when this chocolate made the Assam tea taste simply dreadful!
• With the Vosges Super Dark Coconut Ash & Banana, the coconut came to the fore, much more so than with the Assam yesterday, but the tea was lost. The "browner" warm flavors of the tea activated the warm receptors, which in turn expanded the coconut effect, so my ability to sense the "greener" cool flower flavors typical of the tea was inhibited,
• Confession time: I don't like white chocolate — too sweet and too vanilla-y.** I didn't like it any better with this tea. Worth noting: I brewed the tea for a relatively short time, so there was not much bitterness (it takes time for EGCG to come out of the leaf), so there wasn't much to counteract the excessive sweetness of the chocolate.
• Finally, the Ghirardelli 100% cacao, which I love by itself — sad to say, the tea tasted like so much hot water...so different from yesterday, when even the little bit of Assam I had left complemented the chocolate very nicely.
**More confession time: I had my DNA tested, and looked up info about sensitivity to sweetness. Turns out that I have the DNA variants that program for high sensitivity to sweet. Also to bitter, but I do like 100% cacao chocolate...go figure!

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TEA & CHOCOLATE PART 1: ASSAM

(This is the first of a series of tea and chocolate pairings, first discussed on the Pairteas Facebook page.)

From left to right in the picture:

Ghirardelli 100% cacao, Vosges Super Dark Coconut Ash & Banana,

Chocolove (appreciate the name!) Ginger Crystallized in Dark Chocolate, and Ghirardelli White Chocolate. 

Found some very nice Assam and tried it with these chocolates. 
• First, have to say that all the chocolates were pretty good by themselves, even the coconut one and I don't much like coconut. The dark chocolate dominated the coconut flavor, however, and the banana was nowhere to be tasted, so the net effect was just slightly coconutty.
• Started with the chocolate with ginger: OMG was that dreadful! It made the tea taste bitter and sour, and the chocolate was pretty bad too, even when by itself it was pretty good. It has a low cacao content by my standards (65% — I enjoy 100%), so the ginger, which hits the cold receptors, stands out compared to the chocolate. Assam tea hits the hot receptors, so the net effect is that bitterness and sourness have a chance to come to the fore, which does neither the tea nor the chocolate justice.
• Next, the coconut banana chocolate: it made the tea smoother but less rich, practically hot water. Coconut, even when turned presumably into charcoal for this chocolate, and banana both hit the warm receptors, so even with 72% cacao, the warm receptors had a chance to turn the hot receptors off. Net effect: nothing special for either the chocolate or the tea.
• Then I tried the white chocolate: the white chocolate tasted nice with the tea, though within a short time, the white chocolate came to dominate and the tea disappeared, except for a slight herbal flavor. This result is not surprising: white chocolate has no cacao, but does have cacao butter and vanilla and a ton of sugar (first ingredient on the list). All of these turn off the hot receptors, leaving the cool/cold receptors less dampened, which allows the herbal aspect of the tea to peek out. Think of adding milk and sugar to Assam teas.
• By the time I got around to the 100% cacao chocolate, I had pretty well run out of tea, so you will have to wait for those results. Hint: not bad!

PEANUT SATAY and GREEN TEA: CAN THEY PAIR WELL?

Here's the latest post from my Facebook page, with the conversation I had with Marzi after the post:

Picture of tea service grabbed from Bangkok At Beltline webpage.

Interesting question that came to mind when Pairteas friend Marzi Pecen sent me images from a Thai Afternoon Tea event at "Bangkok At Beltline" near her home in Texas. She mentioned that green teas were paired with the savory dishes, while a chrysanthemum tea was paired with the sweet ones. 

Noticed that the first savory dish on the menu consisted of mini chicken satay sandwiches. Which brought the question of peanuts and green tea to mind. The answer, I think, is yes, depending on what you want to experience in the tea and the food:
• Green tea, as we have noted before, hits the cool/cold receptors, to give a fresh, "green" herbaceous flavor.
• By contrast, peanuts, thanks to the cooking process, mainly hit the hot receptors. Add the chilies in the satay sauce and the receptors will be going full blast...
• ...except that the oils in the satay sauce will dampen the effect of the chilies!
• At the same time, the salt and the savory in the chicken/satay combo will turn off the receptors for bitterness, with a net effect that the tea will taste sweet.
• (And I should mention that some people have found compounds in roasted peanuts that could be qualified as "green' and vegetal. Don't know whether this holds true in a satay sauce.)
=> What's the result? Here's my guess: the first bites of the mini chicken satay sandwich won't be too spicy, and you will be able to taste the tea, but it will be sweeter than expected and somewhat less vegetal—a nice "palate cleanser" that cuts down on the heat. As you progress through the sandwich, however, the hot receptors will dominate (they're slow on - slow off), and the flavor of the tea will disappear. Note that the sandwiches were tiny, though, so you may not have gotten to the point of hot receptor domination...

So I asked my friend: What did you experience, Marzi? 

Here's what she said:

Marzi Pecen Yes! The chicken satay sandwich was sweet & savory in the first bite. The heat did increase and linger. This was true with the mini-veggie samosa as well. Between conversation and bites of savories, the Chinese green tea (toasty, nutty, no astringency) was a nice palate cleanser and enjoyable on its own.
I was happy to see that they paired different teas with each course and noticed that other tables were excited to try something new. The service was attentive and the food inventive yet approachable.

PairTeas Ah a Chinese green tea, so more toasty nutty "brown" flavors. Did you drink the tea first, then eat the food, or vice versa?

Marzi Pecen We started with the tea. But I also alternated with sips of water.

PairTeas Was the tea greener tasting before you ate the savories?

Marzi Pecen I wasn't thinking specifically of that, but I noted it seemed toastier after the savories. Especially the nicely browned croissant.

PairTeas Isn't fascinating how you can change the flavor profile of a tea with pairing? The Chinese green teas are pan-fired so they have some of the toasty "brown" flavors, which can be brought out by pairing with the "brown" savories; a gyokuro would never work.

Marzi Pecen One think I really appreciated was getting to taste Thai tea unsweetened and hot. Delicious. It was paired with a small very rich & dark chocolate tart whose complexity was emphasized paired with the tea. The beautiful green tea and Thai tea macarons would be over powered by the tea so, after a bit of water, I savored those. They were sublime. The buttercream between the meringues were perfect and true tea flavors.

Here's the treat tower — how delicious it looks!

Menu and Treat Tower Photos by Marzi.

Caffeine, L-theanine, and EGCG, and timing of effects

In the previous post, I looked at the calming effect of a single dose of plain EGCG at 3 hours after consumption. I was wondering: why 3 hours? 

Found out that it takes at least an hour and a half for EGCG to be absorbed and to reach the brain in sufficient quantity. Hmm...

What about the two other compounds in tea that may have an effect on the brain, namely caffeine and L-theanine*?  Caffeine gets into the brain very quickly—within 30 minutes—and seems to leave pretty quickly too. By contrast, L-theanine takes its time—it reaches its peak after an hour, and levels dwindle more slowly.

David Camfield and his colleagues think that this difference in timing may explain why experiments using caffeine and L-theanine have yielded mixed results when it comes to mood and cognitive (= thinking) performance. They did a meta-analysis of a large number of published studies of the effects of caffeine and L-theanine together and came to the conclusion that the effects were mild to moderate at best.**

However, all of these studies involved a single dose of the compounds given together at a single time point. This is not at all how we drink tea! 

Instead, we usually sip tea over a rather long period of time—time enough to build up L-theanine levels and even EGCG levels, while keeping caffeine levels up all along. It's as if your brain were given all the compounds simultaneously in a continuous infusion. 

You may even have noticed a time sequence when you sip your tea, first arousal from the caffeine, and then, when the L-theanine kicks in along with the caffeine, an ability to focus, followed by a sense of calm coming from the EGCG.

Is that what you have experienced?

* L-theanine is a non-protein amino acid found almost exclusively in tea. 
** 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 Reviews, ISSN 0029-6643, 08/2014, Volume 72, Issue 8, pp. 507 - 522