guest post: the science of taste

It's a GUEST POST!  I wasn't able to go with Caitlin to The Science of Taste Through Cocktails because I had a deadline the next day, but she's here to tell you what I missed.  Take it away, Caitlin. --bk

A few weeks ago, I was lucky enough to nab a seat at The Science of Taste Through Cocktails – the first in a series of seminars organized to benefit the Science Club for Girls and co-sponsored by the Boston chapter of LUPEC (Ladies United for the Preservation of Endangered Cocktails). For the price of the ticket, I got great conversation, interesting lectures, and fantastic drinks, and supported getting young women into science while doing it – pretty sweet deal!

On arrival, I received a dainty cup of LUPEC’s Welcome Punch, based on an 18^th-century recipe consisting of green tea, cognac, rum, and lemon – a nice mix of sweet and tart, and very drinkable. Had I not been so committed to finding and keeping a good seat (the event was sold out and the little room was well-packed), I probably would’ve gotten myself indecently soused on it before the evening even began.

After everyone was settled in and the necessary introductory speeches made, Don Katz, an Assistant Professor of Psychology and Neuroscience at Brandeis, dropped some science on us. He began by identifying the five main taste categories we’re able to perceive and their importance: saltiness (which signifies a food contains important electrolytes), sourness (usually an indication of unripe fruit that’s not ready to eat), sweetness (ripe fruit; delicious calories), bitterness (poison!) and umami (or as Dr. Katz, called it, “umamiocity”) which was “too complex to fully examine here” (the awesome mystery of umami strikes again).

Now, you’re probably dredging up the memory of the ‘five different sections of the tongue’ thing from seventh grade Biology class. As it turns out, like many things you learned in seventh grade, that’s total bullshit. Every part of your tongue can perceive all the different taste categories equally well. What you do have is millions of taste buds, each of which is shaped like an orange and contains sections which look like orange wedges; housed within these wedges are a variety of cells which react differently to different tastes.

From there we got into a discussion of neural pathways and how your brain interprets the sensations from your tongue. Particularly interesting is the bitterness reaction, involving a “rejection pathway” which is basically this:

Mouth: Nom nom nom.

Brain: Bitter?

Tongue: YES!

Brain: SPIT IT OUT!

Mouth: BLEH!

This rejection pathway is so basic it only involves the brainstem – no higher brain function! Even creatures with ONLY a brainstem have this reaction. Katz showed us videos of frogs, babies and mice exhibiting the same ‘rejection pathway’ reaction – mouth agape, tongue stuck out. We covered again how this reaction serves a basic protective function: bitter foods are usually poisonous to us; sweet foods are usually safe to eat and provide life-sustaining calories. However, as Katz pointed out, this doesn’t always bear out. There are all sorts of bitter greens, like kale, that are fantastically good for you, and sweet things, like the manchineel fruit, that are extraordinarily poisonous.

[Well shit, now I want to know what the manchineel fruit tastes like, I bet it's awesome. --bk]

Katz then highlighted how all five senses integrate to affect our perception of taste. Touch, for example: carbonation has a negligible effect on the chemical profile of soda pop, but it’s the sensation of the bubbles in our mouths that affects our perception of its taste (and thus why most people hate flat soda).

Then there’s vision: Katz likes to perform an experiment with his students where he segregates drink sodas from their expected colors. He dyes an orange-flavored drink purple, a cherry-flavored drink yellow, a lemon-flavored drink red, etc. Without fail, the students taste the flavor they expect the drink to be based on its color – even after they’re told otherwise!

As for smell, most of us are familiar with how closely it governs taste – we’ve all held our noses when choking down something unpleasant, or suffered through tasteless meals during a bad cold. But apparently this works just as powerfully the other way: many fruit-flavored candies (like Skittles) don’t have different flavors, just different colors and aromas, and that’s enough to make us think they taste different. Some candies only differentiate by color (as with Katz’s beverage experiment) -- but for our brains, this sideshow charlatanism is sufficient.

Finally, there’s social experience. Katz raised the obvious example: tequila. Everyone knows someone (or is someone – ahem) who hates tequila because their first (and last) experience with it began during a party and ended kneeling in front of a toilet. From that point ever after, tequila is almost inextricably associated with nausea. But this can also work positively: in lab experiments, if a rat has just eaten food and breathes it onto another rat, that second rat will reliably choose that particular food over everything else, even if it’s bitter. Presumably humans need a bit more than some heavy breathing to get into something they mightn’t normally eat, but most of us can think of something we started eating or drinking because of social influences, even something we might otherwise have found repulsive. (Spam, casu marzu, etc.)

Now that we were all properly educated on how and why we taste the way we do, it was time for cocktails!

First up: Sour, by Augusto Lino from Upstairs on the Square.

This was Lino’s variation on a Last Word, and consisted of 1 part spirit base (gin), 1 part sweet (chartreuse) and 1 part extremely sour (verjus). On my first few sips, it didn’t taste any sourer than any other Last Words I’d had, and it was deliciously chartreusey, but it had a tarter, drier finish that must have been the verjus. Looking around the room, you could see (and hear!) everyone smacking their mouths after every sip – a good sign that sourness had been achieved. Lino passed a bottle of verjus around the room and encouraged us to smell it. My first impression was a strong smell of cedar (but I grew up in the Pacific Northwest, so that may just be me smelling what I know – let’s not forget the powerful links between taste, scent and memory). After a couple more whiffs, I could definitely smell a musty, almost vinegary, but very grapey scent. I suggested to the neuroscience student sitting next to me that we smell the bottle and then immediately drink some of the Sour to see if the verjus flavor was more pronounced – and it was! That tart, dry finish now tasted more like a hint of very dry, sour white wine. SCIENCE!

After each cocktail, former chemist and current opera singer Graham Wright spoke a little bit about the chemical aspects of what we were tasting. In this case, sour drinks are highly acidic, and acid reactions involve the donation of protons – the smallest particle you can taste. Note to self: invent and market sour drink called Mouth Fulla Protons.

Next up was Umami, by Nicole Lebedevitch of Eastern Standard.

She had mucked around with a few different savory bases, like miso and soy, without much success. The mix she finally ended up with was mushroom gin, Madeira, orange juice, honey and salt. I have to admit, I was wary of this when I saw this on the menu. “Mushroom gin?” I thought. “Is this going to taste all fungal and dirty?” In fact, it was my favorite of all the cocktails that night: mouthwateringly delicious and compulsively drinkable. The first thing I tasted was a nice, sunny sweetness, but then, as it was going down, an amazing earthiness hit the back of my mouth and around the sides of my tongue, right where you salivate – and I did. THAT was the mushroom gin. It didn’t taste overtly mushroomy, but it had that rich, earthy bottom note that makes fungi so satisfying and delicious. I could’ve had five of these. The other people at my table all said the same: “This is so different, but great! I can’t stop drinking it!”  

Wright talked about tannic acid being an important element in the perception of umami, as well as glutamate (like in MSG). Glutamate’s a neurotransmitter, and according to Wright, the perception of umami involves the most basic kind of neurotransmission, and yet the perception of umami varies widely across cultures: compare American attitudes to Asian attitudes towards MSG, or Australian and English preferences for Vegemite and Marmite.

That set up a great segue into the next cocktail, Salty -- and boyyyy was it ever.

Emily Stanley, the brand ambassador for Bols Genever, busted out a Michelada variation, comprised of Pacifico (Stanley: “any cheap Mexican beer will do”), lime juice, Worcestershire sauce, soy sauce, Tabasco sauce, and a salted rim. The first thing that hit me was the bubbles from the beer, then a salty, earthy, savory body (almost like broth) and a spicy aftertaste. It was the only drink I couldn’t finish, but it was cool. At this point, the appetizers had hit the table, including some little teaspoons of ceviche. My tablemates and I thought the drink would chase a spoonful of ceviche especially well, and we were right – the drink enhanced the flavors of the fish beautifully. A spoonful of ceviche helps the Salty go down – or vice versa.

Wright talked about the cation in salt being responsible for our perception of its saltiness, and how the beer was an important element in this cocktail because it’s great at dissolving the salt (the ethanol in it only slightly less so). Katz said this was the most complex thing he’d ever tasted: the soy sauce contributes amino acids, giving it an umami undercurrent, the bubbles mute and blend the different flavors in the drink, and the Tabasco activates your VR1 receptors, which gives you some heat at the end of the drink. I never would’ve thought to order something like this before, but now, if I were going to have some fish and chips or a few oysters, this would be a much more fun beverage accompaniment than a plain old beer.

After all that complexity, it was pretty refreshing when Joy Richard of The Franklin Café served up her Bitter – a simple, classic Negroni.

Mmm, Campari. This was the most polarizing of all the cocktails – half the people in the room loved that spicy, citrusy bitterness (and I was one of them) – the other half definitely worked their bitterness rejection pathways into overtime. Lots of BLEH! faces, including one poor girl at my table who took a single demure sip, then coughed and sputtered for the next five minutes until she was the same color as the drink. After she’d choked down most of a pitcher of water, she declared the Negroni to be the worst thing she’d ever tasted in her life. Another thing to remember about taste: there’s no accounting for it.

Wright talked about how a large number of compounds can contribute to the sensation of bitterness, but mainly we deal with alkaloids here, which are nitrogen-based and nearly always come from plants. The discussion inevitably led to the distinction between supertasters and non-tasters, and the role of the compound, phenylthiocarbamide (PTC) in the breakdown. Depending on your genetic makeup, PTC will either taste incredibly bitter to you, or like nothing at all. About 70% of the population can taste it, but this number can vary dramatically across ethnicities – only 58% of indigenous Australasians can taste PTC, compared to 98% of indigenous Americans. And supertasters, boy, they can really taste it, although Wright was quick to point out that non-PTC-tasters tend to consume more alcohol. At this point, Katz and Wright, perhaps a little in their cups (they weren’t the only ones) declared that putting vermouth in the Negroni was a “wussy move” and that if Richard had really wanted to go for a bitter drink, she should’ve left it out entirely – perhaps an experiment for another time.

Finally, it was time for the last drink of the evening: Sweet, by Carrie Cole of Craigie on Main -- Bols Genever, St. Germain, Averna, Xocolat Mole Bitters, and a bit of salt.

Because everyone was a little silly at this point, and because this was perhaps the least challenging of all the drinks (which isn’t a slight), I’m not sure this one got the attention it deserved. Cole deftly managed to pull off a cocktail that tasted like really good chocolate – fruity, malty, spicy, rich, herbaceous, and a little bitter – but it was light, with a subtly (not overwhelmingly) syrupy finish. I’ve had a few treacly, stomach-souring chocolate cocktails in my time; this is the cocktail those cocktails wish they could be. They’re the Sixlets to this drink’s Valrhona.  

Sweet’s scientific analysis also suffered for being the last drink of the evening as many were pretty compromised at this point (including me, judging by the state of my notes). There was some talk of different sugars, both naturally-occurring and synthetic (the word ‘chirality’ shows up in my notes encased in brackets with no further explanation – how mysterious!), but before long, the evening drew to its inevitable conclusion and we happy science-tipplers dispersed, mouths delighted and minds enriched – not bad for a Wednesday night in Kenmore.

To find recipes for all the cocktails mentioned, see LUPEC’s write-up of the event. The next installment in the Science of Taste series, The Science of Temperature in cooking, takes place November 16 at the Microsoft NERD Center; tickets can be purchased here and all proceeds benefit The Science Club for Girls.