Taste and Smell

Objective:

To explain in short essays or diagrams how the gustatory and olfactory senses work together to determine flavor, at the level of 85% proficiency for each student.

In order to achieve this objective, you will need to be able to:

Examine the distribution of sensitive sites on the tongue for sour, salty, sweet and bitter tastes.
Examine the separate roles of taste and smell in determining flavor.
Examine the interaction of taste and smell in determining flavor.

Materials:

Group Supplies

Salt Taste: Salty water

Sugar Taste: Sugary water

Sour Taste: Lemon juice

Bitter Taste: Onion juice or tonic water

Toothpicks

6 small scoops of mini jelly beans in three different flavors (lemon, grape, cherry)

6 small paper bags

Methods:

Taste localization on the tongue

Get solutions for each major taste (salty, sugary, sour and bitter). Work in groups of two and have one student serve as the subject and the other student apply the samples and record the regions of the tongue sensitive to each solution. Dip the toothpicks into the solutions and lightly touch the tongue. Use a different toothpick for each solution. Repeat the tests on different portions of the tongue. It may help to drink a bit of water in between tests. Also be careful in testing the back part of the tongue...some people may gag!

Interaction of Smell and Taste

Before testing:, choose students in your group to serve as testers.
The other students in the group will prepare the materials. With a marking pen, identify the bags as either taste or smell bags. Write "taste #1," "taste #2," and "taste #3" on three of the sacks and "smell #1," "smell #2," and "smell #3" on the other three sacks.
Divide jelly beans among the bags so that you have a "taste" bag and a "smell" bag for each of the three flavors. Taste #1 and smell #1 jelly beans should be the same, taste #2 and smell #2 should be the same, and so on. Crush a few of the "smell" jelly beans so the odor molecules can escape into the bag. Close the bags by folding down the top.
Taste Test: Instruct the testers to close their eyes and plug their noses. Choose one of the taste bags and instruct each tester to chew on a sample from this bag. In five seconds, ask them to record on their data table what flavor they believe the sample to be. Repeat the procedure for the remaining taste bags. A small sip of water between samples will help clear away the previous flavor and provide a more accurate test. If they cannot tell the flavor, record "unknown."
Smell Test: Choose one of the "smell" sample bags. Have testers close their eyes, open the bag, and inhale the aroma for 10 seconds. Remove the bag and close the top tightly. Record the flavor of the sample on the data table. Make sure each of them repeats this procedure for the other two samples.
Smell and Taste Test: Use the "taste" bags again. Repeat the procedure as in step # 4, "Taste Test," but do not have your testers hold their noses shut. Be sure, however, that they have their eyes closed. Record their guesses in the data table.

Results:

Map of taste sensitive areas of the tongue

Flavors Perceived

	Smell only	Taste only	Smell and Taste
Flavor # 1
Flavor # 2
Flavor # 3

Discussion:

Are parts of the tongue more sensitive to specific flavors or are all parts of the tongue equally sensitive to the flavors?
Compare tongue maps with the maps from other people.
Which sense, taste or smell, identified the correct flavor most often?
How were the "taste" messages your brain received different from the "smell" messages?
How do you think candy makers simulate fruit flavors?
Why is flavor more intense when you chew a jelly bean than when you suck on it?
If you took the Smell and Taste Test with your eyes open, do you think you could recognize the flavor of a purple jelly bean that has an orange flavor? What data from your tests support your conclusion?