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• Science Fair Project Guide

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• Projects Involving Human Subjects
• Sample Size: How Many Survey Participants Do I Need?

Project Summary

Difficulty	5  –  8
Time required	Very Short (a day or less)
Prerequisites	There are special considerations when designing an experiment involving human subjects. The Science Buddies resource, Projects Involving Human Subjects, has more information, along with links to the official ISEF rules.
Material Availability	Readily available
Cost	Very Low (under $20)
Safety	No issues

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Objective

The goal of this project is to investigate the influence of smell on taste.

Introduction

Click here to watch a video of this investigation, produced by DragonflyTV and presented by pbskidsgo.org

Feeling hungry? How about some spicy salsa with some salty chips? Or if you're more of the health conscious type, then a tasty snack of tangy yogurt and fresh sweet strawberries might hit the spot. All these foods taste flavorful because the surface of the tongue hosts up to 10,000 specialized microscopic taste buds designed to detect salty, sweet, sour, or bitter sensations. Combined together, their signals send wonderfully distinct messages to the brain so we can differentiate the subtle taste of hundreds of different flavors.

Taste is truly a sensory bonanza, but is it totally limited to the tongue? We know that some things affect taste, and being sick is the most familiar example. We simply do not taste food as well when our heads are stuffy and our noses are clogged. Does that mean smell contributes as much or more to taste as our talented taste buds? In the project video, two students set out to answer this question. Check it out to see how they designed a clever experiment to evaluate the importance of smell on taste. Then read on to find out how to set up a similarly delicious experiment of your own.

Julia, Leah, and Folabi wanted to test volunteers' tasting ability when smell was not a factor, so they set up an experiment where their volunteers tried various food samples with nose plugs on and then with the nose plugs off. They also put real effort into coming up with a truly "blind" taste test. Not only did they ask their volunteers to wear covered goggles so they couldn't recognize the color or look of the food, the young experimenters blended and mashed the samples beforehand to disguise the food's typical texture. Seems like the scientific chefs in the video really understood how to construct a good controlled experiment. They limited the food tests to purely taste and smell and eliminated any additional sensory input via sight.

Julia, Leah, and Folabi discovered that when the volunteers wore nose plugs, their sense of taste was less accurate and less intense than when they tasted the food without the nose plugs. So smell appeared to make a difference. Still, nose plugs didn't completely block all ability to taste. So the students did some research on the anatomy of the nose and mouth and figured out that chewing some foods can get aromas to the nose through the back of the mouth even when the nostrils are closed. Do you think you would find the same results in tests with your volunteer tasters and your selection of foods? Well, write out the grocery list, gather up those volunteers, whip out the blender and find out!

Before you don those aprons and chef's hats, be sure to do a little background research on taste and smell. You also might be interested in knowing how the brain receives and processes information sent from taste buds and the nose. We included a list of terms, concepts and questions in the next section to get you started. You'll see the scientific words for smell (olfaction) and taste (gustation) in the list, just in case you want to expand your search or impress your friends. After you have more information on the subject, you might be inspired to design a slightly different experiment of your own. The Variations section below lists some suggestions for you to consider.

Good luck, have fun, and bon appétit!

Terms, Concepts and Questions to Start Background Research

To do this project, you should do research that enables you to understand the following terms and concepts:

• Smell (olfaction)
• Taste (gustation)
• Nose anatomy
• Mouth anatomy
• Taste buds
• Limbic system of the brain
• Cerebral cortex

Questions

• How do we use our nose to smell?
• How do we use our mouth to taste?
• How important is smell to the ability to taste?
• What parts of the brain are responsible for detecting and interpreting smell and taste?

Bibliography

• Good introduction to the anatomy of the nose.
  Gavin, M., 2007. "What's That Smell? The Nose Knows," Kids Health website. [accessed May 9, 2007] http://www.kidshealth.org/kid/body/nose_noSW.html.
• Basic introductory background on the tongue and how we taste.
  Dowshen,S., 2007. "Stick out Your Tongue and Say Aah!," Kids Health website. [accessed May 9, 2007] http://www.kidshealth.org/kid/body/tongue_noSW_p2.html.
• A more advanced tutorial on taste with some useful drawings and diagrams.
  Jacob, T., 2007. "Taste (Gustation)," Cardiff University, UK website. [accessed May 9, 2007] http://www.cf.ac.uk/biosi/staff/jacob/teaching/sensory/taste.html.
• A more advanced tutorial on smell with a detailed neurological description of smell.
  Jacob, T., 2007. "Smell (Olfaction)," Cardiff University, UK website. [accessed May 9, 2007] http://www.cf.ac.uk/biosi/staff/jacob/teaching/sensory/olfact1.html.
• TPT, 2006. "Taste Test by Leah, Folabi and Julia," DragonflyTV, Twin Cities Public Television [accessed May 9, 2007] http://pbskids.org/dragonflytv/show/tastetest.html.

Materials and Equipment

To do this experiment you will need the following materials and equipment:

• 3–4 volunteers to do the taste tests (Note: To see how many volunteer subjects you need, check out the Science Buddies resource Sample Size: How Many Survey Participants Do I Need?)
• Kitchen or area with counters and sink
• Sharp knives to chop some foods
• Mortar and pestle to grind some foods
• Blender
• Mixing bowls
• Cutting board
• A few large spoons
• Plastic spoons
• Small bowls or cups for each sample
• Pitcher of water to clear the mouth after each sample
• Paper cups
• Swim goggles (covered with paper)
• Nose plugs
• Aprons
• Note pads
• Pens/pencils
• Up to 8 different types of food to taste (select foods that represent the different flavors of sweet, salty, bitter, and sour).

  For some ideas, here are the foods included in the video taste test:

  • Salt water
  • Sugar water (you could use honey)
  • Lime pulp
  • Brussel sprouts (cut up and blended)
  • Blended salsa
  • Peanut paste
  • Onion mush
  • Candy mints (chopped and blended)

  Other items you might consider:

  • Fresh fruit that is mashed
  • Other fresh vegetables (green/red peppers, broccoli, cauliflower)
  • Peanut butter (you can thin this with a little vegetable oil, if necessary)
  • Pickle relish
  • Cinnamon candies
  • Candied ginger
  • Pitted green olives
  • Ketchup
  • Mild mustard

Experimental Procedure

There are special considerations when designing an experiment involving human subjects. ISEF-affiliated fairs often require an Informed Consent Form for every participant who is questioned or observed. In all cases, the experimental design must be approved by officials from the fair (SRC/IRB) prior to the commencement of experiments or surveys. The Science Buddies resource, Projects Involving Human Subjects, has more information, along with links to the official ISEF rules.

1. Recruit your volunteers for the taste test. Be sure to ask them if they have any food allergies so you don't include those foods in your samples. Let them know the day and time of your experiment and how long it should take.
2. Make a list and gather up the foods you want to use in your experiment. You might consider having a few extra foods in case some of them don't end up working well as samples or taste too strong or bad to include in your test.
3. Prepare your samples, taking care to make sure the texture of the original food is not too recognizable. For instance, you'll want to completely blend peanuts so your volunteers can't identify the peanuts by the crunch or feel of the nuts. Food like salsa should also be blended so that the peppers and onions are not obvious.
4. You should try tasting each sample yourself so that you'll know if any is too unappealing or strong to use in a blind test with your volunteers. Remember, you are trying to test their ability to taste and identify foods they typically eat, not gross them out.
5. You can probably prepare many of your samples the day before and keep them in the refrigerator overnight, if necessary. Keep in mind that some foods lose their flavors if cut up or blended and stored for too long, so some samples may have to be prepared the day of the test.
6. Be sure all samples are at room temperature when you have your volunteers taste them since temperature can affect flavors.
7. The day of the taste test, explain to the volunteers that they will be trying a group of food samples with the nose plugs on and then the same set of samples with the nose plugs off. They also will wear the covered swim goggles during the test so that they won't be influenced by what the samples look like. Reassure them that they may taste some strong flavors, but you will be giving them food that they normally eat, nothing that is inedible.
8. Do the taste test with one volunteer in the room at a time so that the other volunteers do not hear any responses before it is their turn to try the food samples.
9. Assign each volunteer an identification number so that your data can be recorded anonymously.
10. For each sample, ask the volunteer to describe the type of flavor that they detect. Record their response(s) in your notebook. If they can't really identify any specific flavor, indicate that as can't identify.
11. Next, ask them to try to identify the food. Also record their response and whether they were correct, close, or incorrect.
12. Let the volunteer have a sip of water between each sample so that they cleanse their taste buds before trying the next food.
13. After each volunteer finishes each set of samples with the nose plugs on and without, you can have them remove their goggles and let them see what they have been tasting.

1. Make three large charts listing the food samples down the side and the volunteer's identification number along the top.
2. On one chart, record each volunteer's response(s) about the flavor of each sample when he/she had the nose plugs on.
3. On the second chart, record each volunteer's response(s) when they removed the nose plugs.
4. On the third chart, score the accuracy of each volunteer in identifying each sample with and without the nose plugs. Put "0" for wrong answer, "1" for an answer that is close, and "2" for a correct answer.
5. Compare the volunteers' flavor descriptions when they had the nose plugs on versus when they had the nose plugs off. Were there many changes in description of the food when they took the nose plugs off? Were the words the volunteers used more descriptive when the nose plugs were on or off?
6. On the first two charts, circle the responses that accurately match the food's real flavor. Which food samples had more accurate descriptions by the volunteers? Which chart had the most accurate descriptions?
7. On the third chart, total the values of each volunteer's responses with and without the nose plugs.
8. Do you see any differences in the total number of correct/nearly correct responses to wrong answers between wearing nose plugs and not wearing them? Were any particular foods easier to identify than others?
9. For help with data analysis and setting up tables and charts, see Data Analysis & Graphs.
10. For a guide on how to summarize your results and write conclusions based on your data, see Conclusions.

Variations

• Effect of Temperature: Some chefs insist that certain foods like tomatoes should be served at room temperature in order to fully taste their flavor. Test this idea by refrigerating and/or freezing one or two samples of your foods and having your volunteers try the food at room temperature and then refrigerated or frozen. Do the volunteers show any change in their ability to correctly identify the food? Research the process of taste and smell to see if temperature should have any affect on either of these senses.
• What's more dominant, taste or smell? For some foods, smell might overwhelm our recognition of taste. For example, have the volunteers wear the covered swim goggles and ask them to try a slice of apple. Tell them you want them to smell the flavor of the food while they are eating it. Put a slice of fresh onion under their noses when they start to taste the apple. Do they taste apple or onion? Are there other food combinations like this you could try? What does this result say about our sense of smell?
• Effect of Moisture: How important is moisture or saliva to our sense of taste and smell when we eat? Repeat your original experiment, but ask the volunteers to dry their tongues with sterile gauze before sampling a food. Then have them sample the food and see if they can identify it. They should retaste the food after a sip of water. Is there any difference in having a wet versus a dry tongue or mouth? Does lack of moisture have an equal effect on taste when smell is eliminated (nose plugs on) as when a volunteer can smell (nose plugs off)?

• For more science project ideas in this area of science, see Human Biology & Health Project Ideas.

Credits

Darlene E. Jenkins, Ph.D.

Sources

The idea for this project came from this DragonflyTV podcast:

• TPT, 2006. "Taste Test by Leah, Folabi and Julia," DragonflyTV, Twin Cities Public Television http://pbskids.org/dragonflytv/show/tastetest.html.

Last edit date: 2008-06-17 00:00:00

Career Focus

If you like this project, you might want to think about career opportunities in Human Biology & Health.

Doctor's need information to decide if a person is healthy or sick, if a baby's earache is bacterial or viral, or if the man next door needs medication to lower his cholesterol and prevent a heart attack. The information often comes in the form of results from lab tests. Medical and clinical laboratory technicians are the people who perform these routine medical laboratory tests, giving the doctors the information needed to diagnose, treat, and prevent disease. Learn more about this career: Medical & Clinical Laboratory Technician.