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Key concepts
Taste
Olfaction
Gustation
The five senses
Introduction
Thanksgiving brings a feast of flavors. But when you imagine the mouthwatering meal—the tang of ruby-red cranberry sauce or sweet, cinnamon-scented pumpkin pie—you might notice that you are combining sensory cues. Clearly the senses work together in your recollection, but how much is taste influenced by other sensory information as you eat? In this activity you'll find out by looking at two senses in particular.
Background
Every time you take a bite of food, receptors in your mouth called taste buds pick up the taste of the food you are eating. These receptors are sensitive to five basic tastes: umami (a savory flavor), salty, sweet, bitter and sour. But right above your mouth is your nose, which also plays a part in how you experience food. The nose is equipped with millions of receptors for odor molecules. You can smell a food by sniffing through your nostrils or if air is circulating inside your nose as you chew. The latter occurs because the back of your throat connects your nose and mouth. The only catch is that air needs to be flowing in or out of your nose for the odor molecules to get into the nose—either through the front or the back. This explains why pinching your nose prevents you from smelling food.
Once they arrive in your nose, odor molecules travel to your nose's olfactory epithelium, the area of the nasal cavity where odor detection occurs. While you are eating, your brain receives signals from both your mouth and nose, allowing you to recognize whatever tasty treat you happen to be chewing. In this activity you'll separate the sensations of taste and smell to learn how much each contributes to your recognition of a familiar food.
Materials
• Jelly beans (at least three different fruit flavors works best)
• Pencil and paper
• Plastic sandwich bags
• A partner. You can also work with a group of friends and compare results
• Blindfold (optional)
• Glasses of water (optional)
Preparation
• Separate your jellybeans by flavor.
• Select at least three plastic bags—one for each flavor you want to use in the experiment. Place a few appropriately flavored jelly beans in each bag. For example, one bag could be for mango jelly beans, another for strawberry and a third for banana-flavored ones. Push down on the bags to smush the candies slightly.
Procedure
• Ask your partner to close his or her eyes (or use a blindfold).
• Give your partner a jelly bean. Ask him or her to chew it and guess its flavor. Record the response, along with the correct answer. Repeat with at least two other flavors. You can offer your subject a glass of water between samples to clean his or her palate. How good is your partner at guessing the bean's flavor?
• Tell your partner to pinch his or her nose shut, then hand your partner a jelly bean. Ask him or her to eat the candy and tell you what flavor he or she tastes. Record the response along with the correct answer.
• Repeat the previous step with one or two other jelly bean flavors—you can offer your subject a sip of water in between each to cleanse his or her palate. Record each response, along with the correct answer. Does being unable to smell change your subject's responses?
• With eyes still shut or blindfolded, ask your partner to breath deeply while you open one of the plastic bags that hold crushed jelly beans. Ask your subject to guess which flavor he or she is smelling—record the response and correct answer. Repeat with the other two bags. Is your subject better at guessing based on taste alone or scent alone?
• Switch roles with your partner or repeat the above with another subject. Is it easy to recognize the jelly bean flavor by taste? By scent? How do your results compare with your partner's?
• Extra: You can also try this on a larger group of people and see whether certain groups are better than others under different conditions. For example, are older people better or worse at guessing the candy's flavor by scent alone?
• Extra: For a healthier variation on this experiment, peel and chop two potatoes and two apples. (Have an adult supervise when you use knives or peelers.) You'll notice the peeled apple and potato slices look very similar. Hand either a slice of apple or potato to a partner—don't let your partner know which is which. Ask your partner to take a bite while keeping his or her nose pinched closed. Can your partner tell the difference between the apple and the potato? Can you? Try again with nose un-pinched.
• Extra: In this experiment, subjects can't see the jelly bean's color, but if you want to check whether vision influences how something tastes, set up a soda-tasting experiment. Get three kinds of fruit soda—such as cherry, grape or orange—and one flavor-free carbonated water. Add a few drops of food coloring to the carbonated water. (Try to use a color that differs from the sodas.) Pour your beverages into glasses and ask subjects to taste each one and name the beverage's flavor. Do subjects mistake the colored water for another fruit soda? Does the color of the water trick people into expecting a soda flavor to match the color?Observations and results
Did plugging your nose make it difficult to distinguish a jelly bean's flavor? Could you and your partner recognize a flavor just by sniffing the crushed candies?
When you cannot smell the jelly bean you are eating, you can only taste the candy's sweetness—and that's not enough information to tell which flavor you are chewing. This demonstrates how much we rely on our sense of smell when we "taste" food—much of the experience comes from scents rather than taste itself. This is also why everything tastes bland when you have a cold: Your stuffy nose keeps you from enjoying the full olfactory experience. In addition to scent and taste, other factors including a food's temperature and texture affect how you experience and interpret each bite.
More to ExploreHow does the way food looks or its smell influence taste? from Scientific AmericanTaste and Smell from Newton's Apple
Does our sense of smell and sight affect how food tastes? from Science Fair Projects
The Nose Knows from Neuroscience for Kids
Your Nose from KidsHealth
