Have you taken a close look at your taste buds lately? Go ahead -- take a look! When you stick out your tongue, you see that it's covered in lots of little bumps. We like to think of these bumps as our taste buds, but actually, these bumps are known as papillae. Your actual taste buds are much smaller, and anywhere from 3-100 of them can fit inside a single papilla.1 Take another look at your tongue. Notice how some papillae look different than others? There are actually four different types! Right in the center of your tongue, there are lots of small, skinny papillae that almost look fur-like. These are called filiform, and they don't contain any taste buds. On the front and sides of your tongue there are little round dot-like papillae known as fungiform.2 They usually contain 3-5 taste buds each. The next two types can be hard to see, but take a look all the way at the back of your tongue, near your tonsils. You may be able to make out a few ridges on either side of your tongue. Those are called foliate. On the top of your tongue in that same area, you might see some large, round papillae. These are known as circumvallate, and they, along with the foliate type, each contain more than 100 taste buds each!1
Looking at the positions of your papillae on your tongue may bring to mind a memory from grade school when you learned about the tongue map. The tongue map shows that different areas of your tongue taste different things, like salty, sweet, sour, and bitter. But don't be fooled. The tongue map is a myth! Each taste bud, no matter where it is on your tongue, has the potential to pick up on any of the five known tastes (more on that in a minute).3
Now let's take a closer look at a taste bud! As you can see from the diagram below, a taste bud is made up of two types of cells -- gustatory cells, which do all the actual tasting, and supporting cells, that are simply there to support the structure and function of the gustatory cells. Above each taste bud is a taste pore, which is simply an opening that allows food molecules to come in contact with gustatory cells. Each gustatory cell has a hair-like projection, called (not surprisingly) a gustatory hair, which hangs out near the taste pore all day.
When a food molecule comes in contact with a hair, the gustatory cell sends an electrical impulse to the brain letting it know that a taste happened! The message is sent through the cranial nerve, which connects all of our taste buds to our brain.2
A single taste bud can contain 30-50 gustatory cells each!3 That means your brain is processing thousands of signals from your taste buds at one time. Your brain takes the information your taste buds are sending, and it compares it with memories of things you've tasted before. That's how your brain recognizes what you're eating! A taste is defined as something that sends a chemical signal to your brain through your taste buds. You might be surprised to hear that there are only five tastes: sweet, salty, sour, bitter, and savory.4 Everything else, your taste buds ignore! But we all know there's more to food than just those five tastes, and that's where odor and mouthfeel come in.
Flavor & Mouthfeel
Flavor, in the technical sense, is defined as the combined sensations of taste (from taste buds) odor, and mouthfeel. Mouthfeel means the way food feels in your mouth. It encompasses texture, moisture level, fluidity, temperature, chewiness, greasiness, astringency, pain (like that from hot chili peppers), and any other tactile experience we get while chewing or swallowing. It may seem strange at first to consider the smell and texture as a food to be a part of its flavor, but your brain is already taking into account these things when it's processing whether you find a food pleasant or not. Take beef jerky for example. If you dug into a bag of beef jerky only to find out that it was dried out and tough, you'd call it "bad" beef jerky. Even if it has the exact same taste and odor molecules as a "good" bag, the terrible mouthfeel ruins it! And that's true for a lot of foods, like soggy cereal, warm soda or stale chips.
When it comes to odor, your body smells on autopilot. While you chew and swallow (and breathe), your body is funneling all the tiny floating odor molecules around you (including those inside your mouth) up and into your nasal cavity where your olfactory cells live. You can think of olfactory cells the taste buds of the nose. They operate on a lot of the same principles. They hang a wee hair into the air space, and when an odor molecule comes in contact, they send a signal to the brain, via the olfactory nerve, letting it know what it picked up. But unlike the gustatory cells in your taste buds, olfactory cells can identify thousands of different odors! To name a few: toasty, nutty, fruity, garlic, fatty, fishy, meaty, floral, grassy/green, rancid, and burnt. (Visit Flavornet.org for a complete list of known odors.) Pretty much every aspect of flavor that isn't sweet, salty, sour, bitter, or savory is actually an odor! And that's why odor is so important to the flavor of a food. It also explains why food tastes different when your nose is stuffed up.
Isn't it fascinating to realize all the work your body is doing while you're doing something as (seemingly) brainless as eating? It's kind of awesome. Food's a complex chemical, and so are you!
1. Society of Sensory Professionals. "Taste Anatomy." Accessed September 19, 2013. http://www.sensorysociety.org/ssp/wiki/Taste_Anatomy/.
2. Marion Bennion, The Science of Food (San Francisco: Harper & Row Publishers, 1980), 5-6.
3. Institute of Food Technologists, "Sensory Science 101: Part 1: Taste and Smell" (Power Point Presentation , 2007), slide 7.
4. Amy Brown, Understanding Food: Principles and Preparation, 2nd Edition (Belmont: Wadsworth/Thomson Learning, 2004), 3-4.