a uniqueness to the effervescence

I remember vividly the first time I sipped on sparkling water. 

It was during my second, jet-lag-filled day in Milan when the Italian student coordinators of my study abroad program invited we wide- and sleepy- eyed Americans to "take a coffee" with them at a corner bar. With this wonderfully poetic translation of the activity we're wont to crassly call grabbing coffee, I became instantly enchanted by the idea. And only a small part of that was due to the six hour time difference.

As is customary, the bar served up their smooth-as-honey espresso with a side of sparkling water. At the time I was new to both (I haven't seen the numbers but I don't think Nebraska, where I grew up, has a big market for either), and their newness was enough to strike delight in me with each sip. First a sip of water, then a sip of espresso, perhaps another sip of water, and then it's up to you who gets the final sip as you choose which taste you'd like to have linger. I often still have trouble deciding.

I repeated this choreographed sipping at bar after bar after bar over the next several months. Each time my tongue became awash with carbonation I marveled at this simple little water's transformative effects. When I sipped it before the espresso it made my taste buds feel like they had been renewed, rolling out a Tongue 2.0 with an improved capacity for making bitterness palatable. When I sipped the water after the espresso, it erased all traces of the coffee as if it had never danced across my tongue. 

You see, palate cleansing is sparkling water's main role in its partnership with espresso.

There is a uniqueness to the effervescence, and it has everything to do with its effects on the tongue. So how does it work?

If we're being honest with ourselves, to a newcomer this water, sometimes called seltzer, can be quite - what's the word? - funky. Not many of us are used to water being bubbly. The sparkling factor makes water seem like it almost has...taste. And we're somewhat programmed, for our safety, to detect and avoid taste in water. Ever since I first tried it I've been curious about both its palate-cleansing abilities and the funk factor, and I'm not alone.

Researchers have investigated the effects of carbonation on taste, and found that the particularities of this taste - and, yes, it is a taste - have to do with cells in the taste bud that respond to CO2. These particular cells are the same cells that most intensely respond to sourness. The interaction between these "sour cells" and carbonation results in the production of protons which are "basically simple, sour acid." And so we do, in fact, taste carbonation.

So that's that. 

But what about palate cleansing; does it reliably succeed or is it a fickle victory for taste buds who spend their short lifespan - each lives for about 10 days - responding to such a long and varied parade of tastes that at some point they ease back onto the curb and stop collecting the candy?

Some have written master's theses on the topic, books such as Cooking for Geeks have taken up the challenge, and we seem left with a general sense that palate cleansing is more complicated than spittoons at a wine tasting would have us believe. That is, cleansing is not just about ridding the tongue of previous tastes but also priming it to respond to new ones.

Pairing wine with a meal showcases especially well the two processes that palate cleansing seeks to either counteract or enhance: carryover and adaptation.

Wine pairings are touted as having transformative capacities - enhancing the subtle notes of a dish, bringing forward underlying notes of a well-aged red or coyly-dry white. Sips of wine carryover to tastes of cheeses flavoring them anew, and various food fats - from meat, say - leave behind traces on the tongue that adapt it and change the taste buds' reception of wine's boozy signals.

Whereas palate cleansers work to avoid carryover and the interaction of different tastes, I quite like how adaptation treats substances such as sparkling water or crackers or wine more like palate primers. To me this makes them somehow more visible and more effectual in their own right. And I think they deserve that, funky as they may be. 

An espresso bar worth its weight in beans will be intent on highlighting the nuances of its roasts, and will call in the expertise of sparkling or seltzer water not for its ability to wash away the tongue's history but to adapt it, prime it, for writing an even better future. 

Next time you're offered sparkling water, before you thoughtlessly sidestep it for its flat and free cousin Tap, consider seriously the transformative power it could hold for your palate. 

And if nothing else, at least get your funk on with some bubbly.