Thursday, March 31, 2016

Isn't Italian cuisine remarkable?

Here’s the explanation I promised in the last post—the explanation (with some additions and edits) I sent to Maurizio in reply to his questions about the experiments with thyme, oregano and basil:

Both oregano and thyme have pretty much the same chemical composition but in very different proportions. When I taste oregano by itself, it tastes like wood shavings to me, and when I taste thyme alone it gives the cold, turpentine flavor Maurizio described. Thyme has a chemical that is not in oregano to any great extent, namely alpha-terpineol, which has that flavor. However when you start with thyme then add oregano, you get the major chemicals in the right proportions and the right order in the mouth, and the result is quite delicious. 

[The major chemicals in question are thymol, which mainly hits the cold receptors, and carvacrol which mainly activates the warm receptors. Thyme has more thymol, and oregano has more carvacrol. If you remember from my post on Basic Pairing Principle #3, the order in which you eat a food matters: cold first and warm later seems to work best.] 

Add tomato, especially cooked in a tomato sauce, and the effect is truly marvelous, I think. The cooking gets rid of some of the potential off flavors such as alpha-terpineol, and the tomato helps bring the combination into the “warm” receptor realm. As noted above, the proportions of the chemicals in oregano, the proportion of carvacrol to thymol in particular, favor the warm receptors.

As for basil and thyme: fresh basil has a compound, anethole, which tastes sweet and is very persistent. Activating the sweet receptor as intensely as this inhibits the bitter receptor, so bitterness disappears. Now the warmer notes of the carvacrol in the thyme have a chance to appear, though the initial attack will be cool due to the higher quantity of thymol in thyme. Thymol activates both the cold and the warm receptors, but you need a higher concentration of it to activate the warm receptors, unless the warm receptors are activated by carvacrol or by compounds in basil first.

By contrast with tomato sauce, insalata caprese would be terrible with thyme and oregano because you would get them separately and/or in the wrong order in a mouthful. By contrast, you can add fresh thyme to the basil with insalata caprese because the effect of the basil is long lasting, so it carries over from mouthful to mouthful. In addition, the fresh tomato brings out the basil, as does the balsamico, and the balsamico, in turn allows the sweet to become prominent by inhibiting bitter through its acid. I know that you classically don't add thyme to insult cappers, but I've given it a try infused in the balsamic, and it's delicious.
...Isn’t Italian cuisine remarkable?

Insalata caprese, from Wikipedia.

Wednesday, March 30, 2016

Food pairing and chemistry

The FOODPAIRING blog has a post about tea and tea pairing. Take a look at what they propose:

The people behind Food Pairing have developed a huge database of the chemicals present in different foods. Their approach to pairing depends on matching foods with similar chemical compositions. This  approach yields some unanticipated and interesting combinations, many of which are successful. 

However chemical composition does not always tell you about how a food or a beverage actually tastes. For example, thyme and oregano have essentially the same chemical composition, but in different proportions. Consequently, the flavors you get when you taste each these separately—and especially when you eat first one, and then the other, and then later reverse the order—will be strikingly different.

Here’s what an Italian friend of Pairteas, Maurizio, said when he conducted an experiment of tasting thyme alone, then thyme together with oregano:
"With pleasure, I made the experiment you suggested. I used dried thyme and oregano.Tasting thyme I found a strong terpenic character with a bitter nuance on the tongue… I had some dryness in the mouth.Tasting thyme with oregano I had a different experience. The aroma was less intense but more complex ( floral, good vegetable). In the mouth I didn't find a strong, dominant note: there was a fresh character, refreshing, pleasant and persistent. Evident in the mouth many minutes after eliminating aromatic herbs."
The next day, he tasted these herbs in reverse order:
"I started with oregano: less intense aroma but less intrusive than thyme. After a while I had burning and metallic sensations on the tongue, but not bitter.Tasting thyme with oregano appear dryness and bitterness. There is a fresh character but secondary to those of thyme [and oregano the day before]."
Finally, I asked him to combine thyme and basil, which (unlike thyme and oregano) don’t share the same dominant chemicals:
"I used fresh basil and dried thyme. With basil disappear bitter and dryness. I found intense and persistent sweet and refreshing notes."
You may notice that these herb combinations are familiar—they are commonly used in Italian food, but are used quite differently. Thyme and oregano are to be found in tomato sauces that are cooked for a long time, so their chemistry changes still further. By contrast, basil is used quite fresh, and when combined with thyme for tomato sauces, these sauces are cooked very quickly.

In my next post, I will discuss what is happening here. In the meanwhile, try these experiments and let me know what your take on them is. Can’t wait to hear from you!

Tuesday, March 29, 2016


Here’s an example of basic pairing principle #3, which is:
3. Because you eat and drink over time, you may experience a succession of pairings: this succession should be considered when composing a dish and a pairing.
In reply to my Facebook and blog posts on Bai Hao oolong aka Oriental Beauty tea, Don Mei of said:

“I tasted a Competition Grade Oriental Beauty which was ridiculously fragrant (and paired well with apple fritters and a whisky maple glaze).”
To which I replied:
“That's what is so interesting to me about this tea, Don. It has aspects that go from the cool (as in apple/maple) to warm/hot (as in fritter/whisky with its vanilla overtones). So depending on what you just had in your mouth, the flavor of the tea will reveal itself differently. I had it with delicious ginger molasses cookies—first I would taste the ginger and the cooler aspects of the tea, and then the warmer aspects would kick in along with the molasses. Did you experience something like this with your fritters?
Don Mei then said: 
“Yes the reason why the pairing worked so well was that the evolution of the tea on the palate was very similar to the apple fritters. Bright and fruity at first from the apples and the slight sourness in the glaze and then moving to the warmth of dried raisins, vanilla and caramel notes of the whisky and fritter combination. The tea accentuated all of this moving from fresh citrus start through to sweet flowers and over ripe grapes and finishing with the slight malt and woody notes that come from the oxidation of such fine leaves. YUM!
As you can see, a perfect example of basic principle #3!

An apple fritter, surely not as delicious as the one Don enjoyed. Image from Wikipedia.

The reason that this principle works is that the residence times of foods on their receptors differs by temperature. Cool/cold are quick-on, but they are also quick-off, so the flavor fades quickly, to be replaced by the warm and hot flavors—warm and hot receptors are slow-on and slow-off.

The secret to the pairing above is that both tea and fritter have cold and warm elements. So when you take a bite or you taste the tea, the flavors will evolve just as Don explained.

If you don’t have either tea or fritters with which to experiment, just think of a time when you ate some chili pepper, which hits the hot receptors. The burn builds up slowly, so at first you think it isn’t so bad, then wow! Ow! So you down a glass of ice water—relief! But no sooner have you had a chance to appreciate the coolness, than the heat comes right back! 

PS: In case you can't find them, here are the other two basic principles of pairing:
1. The overarching principle is that a beverage pairs well with a dish when they both activate the same temperature receptors. When they do, the flavors of both stand out together. If they don't, one will dominate, and you will lose the flavor of the other, or the flavors may clash.  
2. If a dish has ingredients that activate multiple temperature receptors, your choice of beverage will dictate which flavors in dish and beverage will stand out.

Monday, March 28, 2016

Another favorite tea of mine—Bai Hao oolong

Been thrilled by the deliciousness of a Bai Hao oolong tea that Donna Fellman sent to me to test as part of our talk on oolongs at the World Tea Expo this June. As my friend, who sampled it with me, said: "It smells so beautiful! Heerlijk!" (That's Dutch for "Delicious"—my Dutch friend thought it was one of the best teas she has ever had!)

Bai Hao oolong shares several characteristics with that other favorite of mine, second flush Darjeeling. First, the plants have to be infested with an insect, which means that the leaves are harvested in summer. In the case of Darjeeling the insects are thrips, and in the case of Bai Hao, the tea green leafhopper. In both instances the infestation leads the leaves to produce defense chemicals. The defense chemical that gives both teas a muscatel flavor is 2,6-dimethyl-3,7-octadien-2,6-diol (DOD for short).

Bai Hao leaves, with arrows showing where the jassids bit.

But that chemical isn’t the only reason for the intense aroma of these teas. Indeed, infestation, along with the treatment of the leaves to create the tea, leads to the release of a number of the “classic” tea chemicals, such as linalool, linalool oxides, and geraniol. These give the tea a cooler floral aroma, that complements the warmer aspects of DOD, as well as those of the compounds produced by greater oxidation, such as beta-damascenone.

Third, Darjeeling is processed like an oolong, as Don Mei (Director of Chinalife Tea in London) pointed out to me a while back.  Both kinds of leaf have a high moisture content, which means they need to have a long withering time. The longer the withering time, the longer the leaves have to produce these aromatic compounds.

Fourth, both teas are oxidized to the point of being almost like black teas. The insects start the oxidation process, the withering continues it, and the lowish temperature heat treatment allows the more gentle formation of still more aromatics, while further oxidation is halted.

Finally, to extract these exquisite aromatics while avoiding bitterness, both teas should be brewed at a lower, more green-tea-type temperature (80-85º C/175-180ºF), and for a somewhat longer time. I can tell when it’s time to drink from the aroma, but you may decide to time your steep, to 1 or 2 minutes.

[By the way, Bai Hao oolong is also known as Oriental Beauty tea, and dong fang mei ren (東方美人)]

Wednesday, March 23, 2016

Spring Break --

Virginia's Pairteas blog is taking a short break—coming back late on Monday March 28th. Meanwhile, I'm still posting daily on!

Tuesday, March 22, 2016

More evidence of the positive effects of training on specific anosmia…

In yet another paper concerning training for specific anosmia (=inability to smell a specific odor), it appears that training with the specific odor can overcome the anosmia.*

Although we have some 400 functional odor receptor genes, it seems that we only express somewhere around a fourth of the possible receptors in our nose at any one time. Croy and her colleagues calculated that it is likely that each one of us has an anosmia to at least one specific compound, simply because we do not express all possible receptors. 

We do not know why we don’t express all possible receptors at any one time. There is redundancy in the olfactory system: most odors activate more than one type of receptor. So you may in fact not need expression of all genetically possible receptors. Furthermore, it may be helpful to limit the number of functional receptors expressed in the nose in order to help the signal from important odors in the environment stand out: if you only express receptors for those odors that are important in your environment, your detection capacities won’t be swamped by signals from all the other possible odorants in your environment. 

This is where training comes in: frequent exposure to an odorant over a couple of months would appear to make it salient in your environment.  Croy and her colleagues found that all 25 of their study participants who underwent training no longer had the specific anosmia that they had manifested before training, as shown in the following figure:

What exactly happens with training is unknown:
  • One possibility, as suggested above, is that you start to express receptors for the odors with which you trained. 
  • Another possibility (which doesn’t exclude the first) is that your entire smell system, from nose to brain, rearranges itself to become more sensitive to signals from the trained odorant.
  • A third possibility is that the trigeminal system in your nose becomes more effective at increasing the gain from a faint subthreshold signal so that it is now actively perceived.
It’s my guess that all of these mechanisms come into play. As Croy and her colleagues conclude:
“We propose specific anosmia to occur as a rule, rather than an exception, in the sense of smell. The lack of perception of certain odors may constitute a flexible peripheral filter mechanism, which can be altered by exposure.”
My conclusion: it is worthwhile to contemplate a training course for tea aromas as well as wine, to enhance your capacity to appreciate the many flavor facets of your favorite beverage. 

Keep your eyes on this blog, because friend of Pairteas Marzi Pecen is hard at work creating such a training system, and I'll let you know when it's ready.

* Ilona Croy, Selda Olgun, Laura Mueller, Anna Schmidt, Marcus Muench, Cornelia Hummel, Guenter Gisselmann, Hanns Hatt, Thomas Hummel. Peripheral adaptive filtering in human olfaction? Three studies on prevalence and effects of olfactory training in specific anosmia in more than 1600 participants. CortexVolume 73, December 2015, Pages 180–187. doi:10.1016/j.cortex.2015.08.018.

Monday, March 21, 2016

(In)sensitivity to another aroma in tea and wine...

Another aroma compound to which people may be insensitive is beta-ionone. It occurs in both tea, particularly oolong, and wine, especially Pinot noir. And there seems to be a conditional insensitivity to beta-damascenone, a significant aromatic compound in black tea and several different types of wine. By contrast, people do not seem to differ significantly in their thresholds for alpha-ionone, a minor component of both tea and wine.*

All of these compounds are also components of orange juice, so Plotto and colleagues used orange juice “pumpout” (which is deodorized orange juice concentrate) and water as carriers for their threshold determinations. Participants sniffed the samples to determine their orthonasal thresholds, then sipped the samples to determine their flavor thresholds.

Participants differed by orders of magnitude in their thresholds for beta-ionone dissolved in both pumpout and water. The same held true for beta-damascenone in pumpout, but not in water. There was no real difference among participants in their thresholds for alpha-ionone.

X-axis: serial dilutions of beta-ionone in water and pumpout.
Y-axis: frequency of thresholds at a given dilution.
Note that there appears to be two separate groups, one relatively sensitive and one relatively insensitive, as manifested by two separate peaks of frequency.

Interestingly, even at each participant’s threshold, beta-ionone gave different odor and flavor impressions. It was pleasant for participants with low thresholds—they characterized it as “floral, grape, sweet, soapy, perfumey” in water, and “floral, berries, soapy, perfumey” in pumpout. By contrast, participants with high thresholds included “musty, cleaner, plastic” for beta-ionone in pumpout, and “herbal, plastic, chemical” for the chemical in water—in other words many less sensitive participants found the odor and flavor of beta-ionone unpleasant at threshold. 

This study leaves a bunch of questions in my mind: First and foremost, what do these threshold differences mean for the enjoyment of wine and tea? Second, could a person be trained to develop a lower threshold for beta-ionone, and if so, could this training improve their experience of wine and tea? Third, would these kinds of differences in threshold exist for other compounds characteristic of wine and tea? Fourth, how does the ability to perceive beta-damascenone play out in wine and tea, if the thresholds in water are not so different? etc….

So much more research to be done!

* A. Plotto, K.W. Barnes, K.L. Goodner. Specific Anosmia Observed for β-Ionone, but not for α-Ionone: Significance for Flavor Research. Journal of Food Science, Vol. 71, Nr. 5, 2006, pages S401-S406.

Sunday, March 20, 2016


Friend of Pairteas and tea connoisseur Marzi Pecen has recently been looking into the issue of olfactory training, and we have been having discussions concerning its purpose and value. Her goal is to create an experiential training that enables people to appreciate the full panoply of flavors in teas. While the training would be fun for amateurs, professionals in the tea world would benefit, just as have the wine experts in the study presented today.*

As you may have seen in the post of March 9th—on odor mixtures and how we experience them—training can have an effect on the experience of odors for people who can already detect the odors. What about training for people for whom the odor threshold is very high, in other words who have difficulty smelling the compound even at very high concentrations? Can training lower thresholds?

As it turns out there are two odorants in wine that are important for wine flavor, namely linalool and diacetyl, for which people’s thresholds vary. Linalool has a cool, floral/citrus odor, while  diacetyl has a buttery odor. Both of these compounds are present in tea.

Tempere and colleagues decided to try to help wine experts with a high threshold develop the ability to smell these compounds. They divided their experts into two groups, one which would be trained on linalool and the other on diacetyl. The participants were given a bottle of the training solution, and “were instructed to sniff the sample bottle everyday for 1 month and note their training times in a logbook. The following instructions were communicated: ‘To benefit from this training, choose a quiet moment and sniff repeatedly two or three times for approximately one minute.’ “

After the month of training, the participants were brought into the lab and their thresholds for the two compounds measured. As you can see from the graph below, participants’ thresholds to the training odor improved significantly, but there was no improvement in the untrained odor. 

Of course, not everyone improved to the same degree. The following graph shows the change for each participant. As you can see, participants varied somewhat in their starting threshold dilution, the group trained on diacetyl more so than the group trained on linalool, which may account for the differences in improvement seen for the two groups.

Another interesting effect: the improvement with training on either compound was greatest for wine growers, merchants, and brokers, and least for oenologists/wine makers. Apparently the initial thresholds for the two groups of wine experts was not different, so a reason for the differential training effect is not clear. Previous taste training, as manifested by some form of degree, showed no effect.

Of course we do not know where, in the path from nose to brain and back, training has an effect. And as I noted in my post of March 9th, odors may be perceived quite differently in the presence of other odors. So how we might scale this type of training up for the large number of odorants in wine or tea is a big question.

Nevertheless, this work suggests to me that all of us could potentially profit from more focussed sensory training.

* S. Tempere, E. Cuzange, J. C. Bougeant, G. de Revel, G. Sicard. Explicit Sensory Training Improves the Olfactory Sensitivity of Wine Experts. Chemosensory Perception. June 2012, Volume 5, Issue 2, pp 205-213. DOI: 10.1007/s12078-012-9120-1

Friday, March 18, 2016

A couple of days off!

Taking a little time off again to explore what we know about the genetics of taste. I will be back with a post on Monday March 21st. See you soon!


Thursday, March 17, 2016


Have been working on a write-up of my experiences and thoughts about pairing, and came up with three basic principles:

1. The overarching principle is that a beverage pairs well with a dish when they both activate the same temperature receptors. When they do, the flavors of both stand out together. If they don't, one will dominate, and you will lose the flavor of the other, or the flavors may clash. 

2. If a dish has ingredients that activate multiple temperature receptors, your choice of beverage will dictate which flavors in dish and beverage will stand out.

3. Because you eat and drink over time, you may experience a succession of pairings: this succession should be considered when composing a dish and a pairing.

I’ll give you examples of each of these principles in future posts. Stay tuned!

Wednesday, March 16, 2016

A small digression for St. Patrick's Day...

The 17th is St. Patrick's Day in Ireland, one of my ancestral homelands, and in here in the US as well, so a great day to go green... tea, that is! and if green tea is too bitter for you, thanks to its quantity of catechins, try it with a tiny pinch of salt on your tongue, or with a salty cracker—salt turns off the bitter receptor. 

Have a piece of dried ginger on hand? drop it into your cup, count to ten, then fish it out again. You won't taste ginger, but the full delicious herbal flavor profile of the tea will come to the fore. That's because the shogaols in dried ginger wake up the cold receptors and help bring out the cool/cold receptor binding compounds in the green tea.

Or leave the ginger in, and enjoy the combination. 

Lemon, as in a slice of lemon, or better yet, a lemon cookie, is great with green tea, but if you want the flavor without the sourness, try a piece of lemongrass in your cup. Both have limonene, which activates the cold receptors and does what the ginger does.

Mint goes great, too, because it too activates the cool and cold receptors.


On my Facebook post for the 17th, which comes on a little after 5pm Eastern Standard Time in the US, I've put a photo of the Gorreana Tea Plantation in the Azores, one of the two places in Europe where green tea is grown and processed. 

Image of the Plantação de Chá Gorreana, Ribeira Grande, Ilha de São Miguel, Açores, from Wikipedia. For more about Gorreana tea, go to

It's Portugal, not Ireland, but ever so green, too. I've been following the weather in Western Ireland over the past several years. With its warm misty almost Mediterranean climate, perhaps Western Ireland could grow tea, too!

Tuesday, March 15, 2016

Genetics of Taste Sensitivity - Part 3: How to turn a PROP non-taster into a taster

In their ongoing exploration of PROP tasting ability, Tomassini-Barbarossa and colleagues from the University of Cagliari, Monserrato, Calabria, Italy, together with Beverly Tepper from Rutgers University in New Jersey, have discovered yet another determinant of the ability to taste the bitter chemical PROP.*

If you remember (see post of March 13), one of the determinants of the perceived intensity of PROP's bitterness is the number of fungiform taste papillae one has. Taste papillae number and shape depend on the presence of an active form of a protein called gustin in their saliva. People with one copy of the gene for the active protein are moderate tasters, provided that they also have an active gene for the PROP receptor TAS2R38. People with two copies of the active version of the gustin gene have an abundance of papillae, and PROP tastes extra bitter to them.

In the work presented in the paper cited below, the authors show how to turn a non-taster of PROP into a taster, despite having two copies of the mutated non-tasting gene! 

People who inherited two copies (one from each parent) of the non-taster form of the TAS2R38 cannot taste PROP by itself. But when it is mixed in solution with the amino acid L-arginine, they can taste it. Somehow, the interaction of L-arginine with the PROP molecule makes it able to attach to mutated TAS2R38 receptors and activate them. 

Apparently, non-tasters tend to have little free L-arginine in their saliva, so they normally don't taste PROP. By contrast, highly sensitive tasters of PROP tend to have a large amount of L-arginine, which greatly enhances their ability to taste the chemical. 

Interestingly, highly sensitive tasters of PROP also tend to find caffeine very bitter, while non-tasters do not, even though caffeine binds to five different receptors. L-arginine can make a caffeine solution more bitter for these people who don't find plain caffeine to be particularly so. 

Just to think what this means for pairing...more to come!

* Melania Melis, Massimiliano Arca, Maria Carla Aragoni, Tiziana Cabras, Claudia Caltagirone, Massimo Castagnola, Roberto Crnjar, Irene Messana, Beverly J. Tepper, and  Iole Tomassini Barbarossa. Dose-Dependent Effects of L-Arginine on PROP Bitterness Intensity and Latency and Characteristics of the Chemical Interaction between PROP and L-Arginine. PLoS One. 2015; 10(6): e0131104. Published online 2015 Jun 23. doi:  10.1371/journal.pone.0131104

Monday, March 14, 2016

Genetics of Taste Sensitivity Part 2 — Salt Taste

Salt taste depends on receptors in two different locations, the taste bud and the trigeminal nerve endings. 

In the taste bud, Type I cells carry the epithelial sodium channel (ENaC). These are the cells that turn off Type II bitterness-sensing cells, as noted in a previous post (Friday, February 19, 2016). Not much sodium is required for this effect—in other words a food doesn't have to taste particularly salty to taste less bitter.

The ENaC channel has three sub-units, the proteins SCNN1ASCNN1BSCNN1G, shown as alpha, beta, and gamma respectively in the illustration below. Together these subunits form a circular opening in the cell membrane that allows sodium to enter the cell.

Diagram of the ENaC channel in Type I taste bud cells.
Image from Wikipedia.

ENaC is blocked by the drug amiloride. If you take this drug, you lose about 20% of your sensitivity to sodium, so we know that this channel makes a partial contribution to salt taste. The trigeminal "hot" receptor TRPV1 contributes the rest.

Each of the ENaC subunits has several genetic variants. The variants in the alpha and gamma chains apparently don't make a difference in sodium sensitivity. However two changes in the beta protein chain make a difference: for people who carry the variants, salt taste is less intense above threshold.*

By contrast, there is a minor genetic variant in TRPV1 that actually increases sensitivity to sodium concentrations above threshold. TRPV1 is associated with pain when activated by heat, ethanol, or capsaicin, the hot ingredient in chili peppers.

The authors of the study state:
"Future studies should aim to examine the attributes of salt taste at these suprathreshold levels and characterize whether individuals perceive the taste stimuli as aversive or pleasurable or salty or painful."
As someone who carries two copies of the more sensitive TRPV1 variant (one from each of my parents), I can assure them that salt can be very painful!

An unanswered question: do people with different variants of ENaC get different degrees of suppression of bitterness with salt?

  • Ahmed 
  • El-Sohemy. Genetic Variation in Putative Salt Taste Receptors and Salt Taste Perception in Humans. Chem. Senses38 (2): 137-145.

    Sunday, March 13, 2016

    Genetics of Taste Sensitivity Part 1 — Fungiform Papillae

    Promised to say something about genetics of taste and smell sensitivity — here is the first installment, about taste papillae.

    As you may already know, we differ enormously from each other in the number of fungiform papillae that we have in the front of our tongues. Fungiform papillae are the little pink bumps on the front part of our tongues. These fungiform papillae house taste buds, with their taste pores that open up to the surface of the tongue. This picture (courtesy of Tim Hanni MW) shows the tip of a tongue with an abundance of fungiform taste papillae, that look like bubbles. The dark spots are the taste pores. The red circle surrounds a taste papilla.

    Brillat-Savarin, the great French gastronome, in his "Physiologie du Gout" mentioned that the sensation of taste resided in these taste papillae. He went on to say (translation mine):
    "...not all tongues are equally endowed [with papillae]; such that one tongue may have three times more than another.  This circumstance explains why, when two dinner guests sit down to the same banquet, one experiences deliciousness, while the other seems to be eating under duress: it's that one of them has a tongue that is poorly equipped, and that the empire of flavor has its blind and deaf people."
    I'm not sure that taste-blind is a term I would use for a person who has relatively few fungiform papillae. Those of you who have few papillae can certainly taste something; it's just that what you taste is not as clearly defined nor is it as intense as it is for those of you with a greater number. I prefer the term "mildly sensitive taster," and reserve the term "taste-blind" for the inability to taste specific compounds... in taste-blind to 6-n-propylthiouracil (PROP). The genetics of the ability to taste this bitter compound has been studied intensively, but has been complicated by the fact that you need not only a specific functional bitter receptor, TAS2R38, but also a sufficient number of fungiform papillae. 

    Tomassini-Barbarosa and colleagues at the University of Cagliari, Monserrato, Italy, have been studying a zinc-dependent compound in saliva, called gustin and also known as carbonic anhydrase VI (CA6), that is critical for the abundance, growth, shaping, maintenance, and survival of fungiform papillae on the tongue. They teamed up with Beverly Tepper from Rutgers University, New Jersey to explore the interactions between gustin function and PROP tasting. 

    The gene for gustin has two variants, one of which yields a functional protein, and the other a protein that binds zinc less effectively, and yields fewer papillae. Furthermore, these papillae are misshapen.

    Here's my interpretation of the data presented by these authors. If you lack the gene variant of TAS2R38 that gives you the ability to taste PROP, you will not be able to taste it, no matter how many taste papillae you have. 

    However, if you do have the gene variant that imparts the ability to taste PROP, then the intensity you experience will be a function of the number of papillae you have, which in turn is dependent on gustin. 

    If you don't have any copy of the functional gustin gene, you will have few papillae, and PROP will taste weak. If you have one allele of the functional version of the gustin gene and one of the less functional one, you have an intermediate number of papillae. If you have two alleles of the functional gustin gene, as I do, you will have an abundance of papillae.**

    The pictures below, from my lab, show tongues stained with blue food coloring. Fungiform papillae do not stain, so stand out against the blue background.

    This top picture shows a tongue with few papillae, which are more oval than round. Although you can't see it in this illustration, the original photo shows few taste pores in these papillae. Though I don't have any genetic data (it was unavailable at the time we took this picture), we know that this person was a mildly sensitive taster, who was furthermore taste-blind to PROP.

    This next picture shows the tongue of someone we dubbed a moderately sensitive taster, who could taste PROP, and for whom food was of great interest and generally felt to be delicious when well prepared. However, no flavor was too intense for this person.

    Finally, this tongue is from someone (me, actually) for whom flavors can become easily too intense, and for whom the taste of PROP is beyond foul. The blue stain only appears slightly and further back in the tongue, while the front is carpeted with papillae. We called people in this category highly sensitive tasters. As I mentioned above, I have two alleles of the functional version of gustin, and this is the result. 

    Though I wouldn't be surprised if there were more factors involved to yield such an abundance of papillae.

    More to come about the genetics of the taste and smell system and what they mean for your own experiences.

    * Melania MelisElena AtzoriStefano CabrasAndrea Zonza, Carla CalòPatrizia Muroni, Mariella NiedduAlessandra Padiglia, Valeria Sogos, Beverly J. Tepper, and  Iole Tomassini Barbarossa. The Gustin (CA6) Gene Polymorphism, rs2274333 (A/G), as a Mechanistic Link between PROP Tasting and Fungiform Taste Papilla Density and Maintenance. PLoS One. 2013; 8(9): e74151. Published online 2013 Sep 9. 

    ** Had me tested for several taste sensitivity markers, and this is one result.

    Friday, March 11, 2016

    Traditional tea pairings: an observation

    Here I am already violating what I said about the blog going on vacation for a couple of days, but I couldn't resist.

    Jo Johnson, of the Tea Blending Sisters, just joined us at the Pairteas Facebook page, so I was scrolling through the Sister's Facebook page and came across a link to Teforia's blogpost on Tea Pairing:

    In it are described traditional pairings from around the globe. What struck me was that—with the exception of the Japanese with matcha—everyone does something to the tea itself: add sugar, butter, milk, etc. I wondered: why?

    Scottish fish and chips, with a milky tea.
    Image from

    That question led me to looking into the different tea preparation methods, and that led me to the observation: long steeping times are the norm in the places discussed.

    Long steeping times bring out the bitterness and astringency of the tea, which not only are unpleasant in themselves, but also effectively mask the flavor of the tea. The classic solution is to hide the bitterness by using either sweet or salt, and to cut the astringency by both diminishing bitterness with sweet or salt, and turning off TRPV1 with fat—astringency is the result of activating bitter receptors and TRPV1 (the hot receptor) simultaneously. What these additions do, however, is to change the flavor profile of the tea.

    So when we think about pairings, we have to take into account not just the qualities of the tea, but also the conditions under which the tea is brewed, and what we would like to add directly to the tea, if anything.

    Douglas Adam & a Short Vacation

    On Douglas Adams' birthday—he was born on March 11, 1952—the Hitchhiker's Guide to the Galaxy's disquisition on tea:


    PS: Virginia's blog is going on vacation for the week-end, so I can get caught up with a lot of work. Look for the next post on Monday March 14th — we'll be talking about the genetics of taste sensitivity!

    Wednesday, March 9, 2016


    One of the goals of wine education, and of tea and coffee education, too, is to enable you to detect and identify the different flavor elements in a sample of the beverage. One way to learn is to identify the different odors individually, and then figure out which odors are present in your glass or cup. This concept underlies Le Nez du Vin kit and its congeners, and is one of the ideas behind the creation of innumerable flavor wheels, including the latest coffee wheel from the Specialty Coffee Association of America. The mark of a connoisseur is said to be the ability to individually recognize the many odorants in a wine, coffee, or tea.

    Here's a tea flavor wheel from the International Tea Masters Association.

    (Don't worry, you're not going blind, this version is too small to read! Go to the link above for a readable version.)

    Before I discuss a recent paper on the subject of odor recognition,* a couple of definitions: 
    • elemental perception is the process of recognizing individual components in a mixture;
    • configural perception is the process of recognizing mixtures as a single odor.
    Another important point: some mixtures of odors yield a configural perception that is different from the elemental perceptions of the individual components. These odors are said to "blend well." One example, used in this study, is the odor of Furaneol® (= strawberry furanone—see my previous post), which smells like strawberry, and ethyl maltol, which has a caramel odor. Mixed together, they smell like pineapple.

    By contrast, some odors still retain their distinctive characteristics after mixing. In the experiments described in the paper, the authors used guaiacol, which has a smoky odor, and isoamyl acetate, the typical odor of bananas. The two odors could be distinguished in the mixture, and were said to be "poorly blending."

    In the experiments described here, Charlotte Sinding and her colleagues asked the question: when it comes to experiencing odors individually and in mixtures, is there a difference between odor mixtures that blend well and mixtures that don't blend well?

    Participants in the study were divided into four groups, two each for each odor combination. For each odor combination, one group was exposed repeatedly to the smell of the individual components and then was asked to describe the odor as they smelled the mixture, and the other group first was exposed repeatedly to the odor of the mixture and then was asked to describe the odor as they smelled the individual components.**

    Even after multiple exposures, participants who were preconditioned to smell strawberry and caramel separately smelled "pineapple" when the two compounds were mixed together, though slightly less strongly so than did those who had not been preconditioned. In other words, for mixtures that blended well, configurable perception dominated elemental perception.

    By contrast, those who were first exposed to the elements of the poorly blending odors were able to identify them individually in the mixture. Strangely, the smoky odor intensity decreased while the banana odor increased in the mixture for those who were first exposed to the individual components. Elemental perception persisted, but somewhat altered.

    Participants who were exposed to the "poorly blending" mixture first, then smelled the individual odors after, the smoky odor developed a slight banana-y quality! In other words preexposure to this mixture led to a phantom configural perception of the individual guaiacol odor.

    Finally—this is my observation—there was a wide spread in people's responses. What I discussed above are the generalities, but clearly there were very important individual differences in how these experiments played out perceptually. Part of these differences are going to be genetic: there are huge differences among people in their genes for perceiving odorants. Part of these differences may be due to experience: we live in a world of odors, but each of us has a different experience of these odors—which came first in our experiences? which was blended with which when we first encountered it?

    This study confirms and builds upon previous studies of mixtures of odorants. So far these studies are severely limited in the number and type of odorants, odorant mixtures, and number of odorants in a mixture. Furthermore, we don't have a table listing elements that blend well or poorly.  

    Which raises a question in my mind about connoisseurship, namely how do we develop it? Do we use kits like Le Nez du Vin, and accept that the odors we perceive in a given wine may be different from what we perceive when we sniff individual odors? If we study with the kit, will our perception of an individual odor carry over to some other quite different odor, as was the case with guaiacol in the experiments presented here? And if so, how will we know that has happened when we sniff or sip an actual beverage?

    And perhaps more importantly, should connoisseurship be based on a consensus of what one should smell? If so, what about the person who perceives odors differently?***

  • Charlotte Sinding et al.
  • Experience shapes our odor perception but depends on the initial perceptual processing of the stimulus. Attention, Perception, & PsychophysicsVolume 77, Issue 5, pp 1794-1806.

    ** The protocol was in fact more complicated than this, with numerous appropriate controls, but this is the gist.

    *** An anecdote: was invited with one of my students to sit in at a senior wine and food pairing class, when the professor broke out a superb bottle of Burgundy wine from 1949 that had been well stored, so in perfect condition. Professor went around the class asking what flavors people experienced. Out gushed a symphony of red fruits and deep thoughts, until they came to me and my student. We said it tasted like mushrooms. Dead silence. Disapproving stares. Professor said: how could that be? We weren't invited back.

    By the way, my student and I both love mushrooms, so we enjoyed the wine immensely. And I think that's what matters.