Six facts on the science behind taste

For Stuart Firestein, an expert in smell and taste, food preferences are a bit more complicated than you might think. Your ability to appreciate anchovies, stinky cheese or chicken liver has a lot to do with how you use all of your senses.

Photos: Kerri interviews Firestein over a French meal

Firestein, chair of the Department of Biological Sciences at Columbia University, is participating in "The Taste of Science," an event at this year's World Science Festival. He spoke with Kerri Miller over lunch at Picnic Market and Cafe in New York City about the science behind taste.

SIX FACTS EXPLAINING THE SCIENCE BEHIND TASTE

1. Taste is a combination of sweet, sour, salt, bitter and umami.

"Most of what... everyone else calls 'taste' we call 'flavor,'" he said. "Flavor is a very, very complicated combination of those five tastes, your sense of smell — about 80 percent of it is smell — and also your sense of feel in your mouth."

Umami is a relatively new taste sensation for Americans. Firestein explained it in a Big Think interview:

It's been known in Asian cuisines for quite some time, since at least the early 1900s when it was first discovered by a Japanese biochemist, and umami is actually the taste of glutamine. I should say umami is a Japanese word that means savory and it's actually the taste of the molecule glutamate, which is an amino acid. We're all made of 20 amino acids. One of them is glutamate, so lots of us have glutamate in them, other animals, plants and so forth. You find very high concentrations in meat, but also in many vegetables and fruits like tomatoes, for example. It's a taste that has come to be recognized in the West at least largely I think because of the influx of Asian cuisine over the last couple of decades and so we now recognize it.

2.Think fish tastes too fishy? Blame nitrogen.

"Fish is an edgy kind of a taste, an edgy kind of an odor that we're never too sure about," he said. "It's a little on the bad side. It's full of amino acids, I should say, and it's full of nitrogen. Nitrogen can often be a harbinger of rot or bad-tasting, bacterial-tasting things. So that's why it's a little dangerous-tasting for us."

3. Cheese or vomit? Butyric acid contributes to the smell of both.

"Butyric acid is found naturally in cheese," Firestein said. "It's responsible for a lot of the cheesy odor in many cheeses. It's a clear liquid when you have it just as a chemical. So I could put it in a bottle and label it 'cheese' and people will take it and sniff it and they go, 'This is wonderful; it has a deep cheesy smell.' Without them knowing it I can take the same chemical and put it in another little bottle and label it, sorry, 'vomit.' They will smell it and they come up to it with trepidation, they smell it and they go, 'Oh, I can't smell that because I'll throw up.' But if you think about it, parmesan cheese and vomit, they don't smell so different. They both have a lot of butyric acid in them, so it's very context-dependent."

4. Our sense of smell is hindered by our walking on two legs.

"We have a much better sense of smell than we think we do," he said. "Most of the good odors in the world are down around eight or 10 inches off the ground... We instead walk around with our noses, you know, five feet up in the air where really there just isn't as much to smell. So we pay a little less attention to it."

5. We can smell foods two ways: Up the nose or through the throat.

A human nose is "narrow at the top, which is where the odors have to get through and if you have any kind of inflammation or sinusitis or allergies, it closes up even more," Firestein said.

Here's a view of the inside of a human nose:

You also smell foods once they are in your mouth.

"We have this pathway that goes through the back of our throat; it goes beyond our palate," he said. "So when you put food in your mouth, you chew it up, you release all these molecules from the food and they go through this back way. Because your glottis is closed so you don't choke on food, the only way for it to go is up. It goes up right onto your olfactory epithelium, or the olfactory tissue, way in the top of your nose. And you smell the food and get a sense of flavor."

6. Vision is a strong contributor to your sense of taste.

When you see food before eating it, you have a lot of expectations and unconsciously guess whether it will be slimy, chewy or creamy, Firestein said.

Firestein explained a classic wine-tasting experiment where the subjects tasted white wines that were dyed red with food coloring. Due to their expectations from the sight of red wine, the tasters listed words typically used to describe red wines: bold, smoky, chocolate.

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