Neuroscientist Gordon M. Shepherd's revelatory Neuroenology: How the Brain Creates the Taste of Wine (Columbia University Press, $25) offers insights into how we perceive wine. Like his first book, Neurogastronomy, this one argues that it's how our brains process the information our senses collect that actually creates what we think of as flavor and texture. This, he says, engages more of the brain than anything else in human behavior.
That said, there's more to the mechanics of how those messages get to the brain than you might think. Saliva has a significant effect on wine. As the bacteria in our bodies mix with the wine, they react with elements in the wine to create different aromatics than the wine exhibited before we sipped it. This can explain why some wines taste different than they smell.
A spot in the backs of our noses only comes into play once the wine can send its aromatics up the back of the mouth. For years I thought that retronasal spot sensed more aromatics because our body temperature had warmed up the wine. That's true, but our saliva makes more changes. And, since my body's natural bacteria is different from yours, it helps explain why you and I might have different perceptions as we taste the same wine.
Shepherd thinks it's necessary to swallow wine to get the full effect of retronasal smell. "There's an aroma burst, after swallowing," he says, referring me to diagrams of fluid dynamics in the mouth and throat. But my experience as a taster tells me otherwise. I get no difference between how a wine tastes to me from actually swallowing it vs. slurping and bubbling it in my mouth, then spitting it out, so that I can stay (relatively) sober.
Shepherd thought for a moment. "As you breathe out, those volatiles can carry from the mouth to the back of the nose. With practice maybe you can train your uvula to be open when tasting, and others can't."
His peers get it wrong, he says, when they claim a poor connection between language and what we smell and taste. Our ability to describe what we taste is no different than describing a painting. "We can describe Van Gogh's paintings of sunflowers. They look like sunflowers," he says. "But it's almost impossible to describe anything nonrepresentational in words to someone who hasn't seen it. The same applies to music."
Does all this devalue tasting notes? Not at all, he says. We all may have different perceptions of anything we encounter, whether it's a movie, a painting, a dish of food or a glass of wine. "When we take the first samples of the bouquet in the glass we start out with a lot in common," he says. "Most of the time we perceive wines more alike than different."
Thanks to Shepherd's work, we can explain better why we might disagree on the details.