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

Astringency!

Diving more deeply into bitterness and astringency ~

As mentioned in my previous post, a major compound of green tea is (−)-epigallocatechin-3-gallate (EGCG) — major in that it comprises about 30% of the dry weight of brewed green tea! One of its properties is bitterness, and another is astringency. 

Looking into the latter, I discovered something in the literature that makes perfect sense, namely that there are at least two kinds of astringency: the dry-mouth puckering kind and the smooth velvety kind.

You may have heard that astringency is due to precipitation of salivary proteins, but that idea has been completely nixed — there are many very astringent compounds that don’t precipitate salivary proteins at all.

Instead, the dry-mouth puckering kind of astringency that EGCG gives us comes from activation of the trigeminal nerve, the same nerve that gives us the burn of chili peppers.

Up until yesterday, when I read a paper by Schöbel and her colleagues*, I thought that astringency came mainly from activating the hot and cold receptors on trigeminal nerve endings in the mouth — EGCG does activate these receptors, too — but it turns out that there may be a separate receptor for dry/puckering astringency of EGCG on the trigeminal nerve that still needs to be discovered! 

Pucker Man by PunkToad,  https://www.flickr.com/photos/83699771@N00/22606844807

As for the velvety smooth astringency, that kind comes from compounds similar to EGCG but with a sugar attached. Interestingly, the velvety smooth astringency has a fast-on fast-off quality, while the puckering astringency lasts and lasts after you have swallowed the tea (or wine). Again, no idea what the receptor is, but it is clearly on the trigeminal nerve, too.

More research needed! So exciting!

* Nicole Schöbel et al. Astringency Is a Trigeminal Sensation That Involves the Activation of G Protein–Coupled Signaling by Phenolic Compounds. Chem. Senses 39: 471–487, 2014.

Taste is in more than the mouth!

Did you know that we have taste and temperature receptors not only in our mouth and nose, but also all the way down the gut, from throat to end? 

We do, and their functions in digestion and metabolism are slowly coming to light. For example, bitter compounds can be toxic, so we start out life not liking bitter, and we refuse bitter foods—that’s the effect of the taste receptors in the mouth. 

Does the GI tract use the same bitter receptors to help reject food? Does the gut tell us “Stop eating!” when we consume something bitter?

Here is where green tea comes in. Green tea has bitter compounds, catechins, that make their way to bitter receptors lining the gut, the same receptors as in the mouth. In an elegant study, Won-Young Song and colleagues looked at the effects of catechins, and in particular (−)-epigallocatechin-3-gallate (EGCG) on hormone secretion in tissue-cultured gut cells and in mouse intestines.*

The result: EGCG induced the secretion of not one, not two, but three different hormones that are known to decrease appetite. Contrast this effect with, say, carbohydrates, which only induce the secretion of one or two of these hormones.

Does this mean that if you drink green tea you will lose your appetite?

(−)-Epigallocatechin-3-gallate, from Wikipedia 

Not necessarily — don’t go downing green tea by the gallon to get skinny. There’s a whole lot more to appetite than secretion of these hormones.

Furthermore, for many of you (as many as 50% of people apparently), EGCG isn’t all that bitter—whether this is due to this gene or different gene isn't known (there are at least two other bitter taste receptors that are activated by EGCG, and which may have a similar action in the gut. So if green tea doesn't seem very bitter to you it may mean that genetically you have receptors for EGCG that don’t work, either in the mouth or the gut. If so, you probably won’t have this hormonal response.  

And of course we must always give this caveat, namely humans may not have the same responses as mice or tissue culture cells... 

...as the saying goes, more research is needed!

* Won-Young Song et al. (−)-Epigallocatechin-3-gallate induces secretion of anorexigenic gut hormones.J Clin Biochem Nutr. 2015 Sep; 57(2): 164–169. Note: this article is freely available on the web.

Oolongs, between green and black

So excited to be presenting at World Tea Expo with Donna Fellman of the World Tea Academy! We'll be showing off the organoleptic properties of oolongs in our Skill Building Workshop. 

To get ready, I've been looking at the most recent work on oolongs, and came across a paper* where the authors not only did an analysis of the chemicals in the aroma of three different oolongs, but also had trained tasters evaluate the teas for roasted, sulfur, sweet, floral, and green/grassy qualities. They then correlated these qualities with the various aroma chemicals they found.

What struck me: that not only were there positive correlations between chemicals and these qualities, but that there were also negative correlations.

What do these negative correlations mean? That certain chemicals inhibit our ability to sense other chemicals. As the authors put it:

"Positive as well as negative correlations suggest that the perception of an aromatic note was influenced not only by the presence of a few compounds whose aroma forms the attribute but also by the presence of other odorants that affect negatively in the perception of such aromatic attribute." 

The results fit perfectly with my own observations concerning hot, warm, cool, and cold receptors. These receptors are mutually inhibitory, so that hot inhibits cool and cold, and vice versa.

With DaHongPao, which is closer to black tea in its processing, roasted aromas (hot receptors) decreased the ability to sense grassy and green aromas (cool/cold receptors) even though green/grassy chemicals were present in the tea. By contrast, with DongDingWulong, which is closer to a green tea, green/grassy aroma chemicals were more abundant than roasted aroma chemicals, so the roasted aroma chemicals were "hidden." 

You'll experience these differences and more in our Skill Building Workshop, so don't forget to sign up for World Tea Expo, June 15-17, 2016, in Las Vegas: http://www.worldteaexpo.com/wte16/Public/enter.aspx.

Here's the spider graph from the article showing the average scores for each of the qualities:

DHP = DahongPao; TGY = TieGuanYin; DD = DongDingWulong.

* JianCai Zhu et al. Comparison of Aroma-Active Volatiles in Oolong Tea Infusions Using GC−Olfactometry, GC−FPD, and GC−MS. J. Agric. Food Chem. 2015, 63, 7499−7510.

  

Hello Friends and welcome to Virginia's Pairteas blog! 

=>> where you will find a curious potpourri of facts and fun concerning tea, food, biology, chemistry, and more!

For those of you who haven't met me, a few words about my background, and the why of this blog.

Ever wonder why you like foods that other people dislike and vice versa?

That's a question that troubled me since my earliest days, when "try it, you'll like it" was to me an invitation to stroll through a minefield. 

That's why it took all the persuasive powers of the English ladies around me to get me to try my first tea.

We (my family and I) were returning from a long summer and fall in Europe visiting our English and Dutch family for the first time after World War II. We were sailing home on what was probably the least luxurious of Cunard's liners, the Media. She and her sister ship the Parthia were mixed cargo and passenger ships (mostly cargo). Unlike grander ships, she only had one small "grand salon" where the passengers congregated and tea was served almost constantly. The English ladies on board made a bee-line for me, probably because I was one of just two little girls on that extra long and extra boring trans-Atlantic trip—no fancy entertainment like on cruises nowadays  (The other little girl was my sister, who was very young and very afraid of strangers, so glued to our mother).

Learning that I had never tasted tea, the ladies concentrated on the task of getting me to taste it, adding sugar and milk and lemon in various combinations to make it less bitter. Their task was made somewhat easier by the fact that I believed tea was a grown-up drink, so it was exciting to be allowed, nay, told to drink it. I kinda liked it, thought it was better with just lemon (those were the days when I could happily suck on a lemon till it was dry, and I didn't like milk very much). 

Postcard picture of the Media—the passenger area was the white part above the black hull. For more about the Media, go to http://www.liverpoolships.org/media_and_parthia_cunard_line.html

That was the last of tea for me for many many years. My family were exclusive coffee drinkers, which—when I think about it—is surprising, given my Dutch and especially my English and Irish heritage. 

Fast forward through a French baccalauréat, an undergraduate degree in physics, a medical degree, board certification in pediatrics, and a postdoctoral stint at Rockefeller University in immunology, all of which led me to join the faculty at Cornell University. 

After starting in Biochemistry, Molecular and Cell Biology, I ended up in the Division of Nutritional Sciences. The focus of the Division is mainly on diet and what foods do to you metabolically, and on how to get enough food (food security), so it took me a while before I got around to my burning question: why do people differ in their liking of food? 

Why this question? Because I am one of those people with an extensive catalog of flavors that I absolutely love (for example anything spinach or black licorice) and an equally extensive catalog of flavors I absolutely hate (such as green beans and fresh corn). Couldn't help wondering all my life why so many people hate the flavors I love, and love the flavors I hate. And why some people love everything provided its well prepared, and some people don't care much about flavors to begin with and are indifferent toward food.

Don't worry, we'll be getting back to tea soon, because this burning question led me to carry out research on flavor sensitivity at the biggest food service show in the world, the National Restaurant Association's annual show.

Why the National Restaurant Asssociation? Well, it attracts thousands of people with an interest in food, and it has 6+ miles of booths. People's feet get tired, so a booth with chairs is always attractive, and while you are resting your feet you can complete a survey and do a taste test, please.

That way we got enormous amount of data which will take me another lifetime to sort through, from people's choices of where to sit in a restaurant to where they work in a restaurant, and all related to flavor sensitivity.

In 2007, a person came to my booth, took part in the study, and then on leaving said I would hear from him. Didn't think much of it. But this was Scott Svihula, tea master. Two years later he contacted me, invited me to World Tea Expo 2010 and lured me into the world of tea. 

Now to the question: "why this blog?" 

Several World Tea Expos later—in other words, this past year—I started maintaining a Facebook page in earnest, posting nearly every day. As I began to delve into chemistry of tea and the biology of flavor, the posts got longer and longer, and the pearls of tea and flavor knowledge I was sharing got lost—Facebook doesn't have an index, and it isn't easy to go back to past posts. Friends of the Facebook page suggested that I start a blog, so here I am!

Looking forward to communicating with you and hearing your thoughts!!

Will be posting several times a week. Will be announcing the posts and other important stuff on http://www.facebook.com/pairteas