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A Tasty Experiment

cat sniffing apple

Activity from Teachengineering.org is  part of a lesson on the importance of smell developed by Duke University’s Pratt School of Engineering. 

Grade level: 3-7

Time: 90 minutes

Summary

Student teams in grades 3 to 7 learn the key role that smell plays in being able to recognize foods by conducting taste tests while holding and not holding their noses. They then create bar graphs comparing the number of correct identifications for the two experimental conditions.

Engineering Connection

Chemical and food engineers use information about how people sense taste to develop artificial flavors closer to the real flavors they are designed to mimic.

Standards

Next Generation Science Standards

Use a model to describe that animals’ receive different types of information through their senses, process the information in their brain, and respond to the information in different ways. [Grade 4]

Common Core State Standards for Mathematics

  • Draw a scaled picture graph and a scaled bar graph to represent a data set with several categories. Solve one- and two-step “how many more” and “how many less” problems using information presented in scaled bar graphs. For example, draw a bar graph in which each square in the bar graph might represent 5 pets. [Grade 3]

International Technology and Engineering Educators Association

  • Compare, contrast, and classify collected information in order to identify patterns. [Grades 3 – 5]

Prerequisite Knowledge

  • An understanding of what a biological adaptation is.
  • Ability to construct a bar graph (helpful, but not essential).

Learning Objectives

After this activity, students should be able to:

  • Explain the importance of the sense of smell to the ability of humans to recognize familiar foods.
  • Explain why it is adaptive for an animal to use its sense to identify food as being either nutritious or noxious.
  • Create and interpret bar graphs comparing quantities of different itemsCelebrating Science-Bed Bugs...Chocolate... and Beyond
Image: USDA scientist Mary Strem with visitor smelling cocoa husks at the Sustainable Perennial Crop Lab in Beltsville, Md.

Materials List

  • Yogurt or pudding, 4 different flavors, 8 to 12 ounces each (use the larger amount for class sizes greater than 24); if using yogurt, choose types that are “blended” and do not contain bits of fruit that might provide clues due to texture. It is not necessary to have all four flavors be either yogurt or pudding; for example, it would be fine to have two different flavors of yogurt and two different flavors of pudding. Note: See the Safety Issues section regarding food allergies.
  • 4 cup or bowls capable of holding at least 8 ounces
  • ~100 plastic spoons
  • 4 watches with second hands
  • 4 cardboard shoe boxes or similarly sized boxes without lids
  • 4 towels, t-shirts or pieces of fabric that are just large enough to drape over the boxes
  • 4 trash receptacles
  • 16 copies of the Tasty Experiment Datasheet, give each group four datasheets, one for each of the four stations

Introduction/Motivation

After completion of the Can You Taste It? associated lesson, students should be sufficiently motivated to conduct the experiment, and need no further introduction.

Procedure

  1. Make sure all students know how to use the watches to determine when 15 seconds have elapsed. Explain that this is the amount of time that students are allowed before they must state the flavor of the food they just tasted—or else state that they are unable to identify it. Since students take turns being the timers, everyone must be able to determine when 15 seconds have elapsed.
  2. Explain the basic procedure for the experiment, as follows:
Point out that the room will be set up with four tables to serve as tasting stations, and the class will be divided up into four groups. Each group rotates through the four stations (and each group uses four datasheets, one at each station). At each station, two members of the group sit on one side of the table. One of these two members serves as the “feeder,” because s/he feeds the food to the other students, who try to identify it. In front of the feeder is the food to be tasted; it is inside a box that is turned on its side so the rest of the team cannot see the food. One at a time, the other members of the team come to the table.The feeder puts a small amount (about one-half to three-quarters of a teaspoon) of food on a clean spoon, and gently feeds the student.
Meanwhile, the other member seated at the table is the “timer.” This student tells the feeder when to put the food in the taster’s mouth, and then announces when time is up 15 seconds later. Sometime during that 15 seconds the taster must identify the food, or else “give up.”
Mention that that the taster must state his or her answer very quietly, so that other students who have not yet tasted that food do not hear. Also mention that the taster must identify both the type of food and its flavor. For example, if the taster thinks the food is Jello®, s/he says orange Jello®, cherry Jello®, or whatever flavor s/he thinks it is. Once the taster has given his or her response, the timer and presenter record that response on the datasheet provided.
  1. Make sure that all students know how to fill in the datasheet, starting with identifying the tasting station number, and then listing the names of the team members that hold their noses in the left column. They enter the names of the team members that do the tasting without holding their noses into the third column, and once the taste-testing begins, they enter response of each student into the appropriate “Response” column. If the taster does not give a response within the 15 seconds, the response is recorded as “none.”
  2. Divide the class into fourths, with each quarter comprising a team. If necessary, ask for help in rearranging the classroom to set up the four tasting stations.
  3. At each station place one-fourth of the spoons, a trash receptacle for the used spoons, a watch and a box containing a cup or bowl of food to be tasted, but cover the box with the fabric while it is in transit so that students are not able to see its contents. Also place a copy of the datasheet at each station, and a placard with a number between one and four to indicate the number of that particular tasting station.
  4. Have each team choose two of its members to serve as the timer and the presenter for the first station. Have the remaining team members decide which half to hold their noses and close their eyes, and which half to only close their eyes. For teams with an odd number of students, have the extra student hold his or her nose and close his or her eyes while tasting. Be sure to explain that as they rotate through the different stations, every student will have an opportunity to do both types of tastings, and most will have an opportunity to be the presenter and/or the timer.

 

Body of Activity:

Part 1: Doing the taste tests

Once the class is clear on what is to happen, assign each team to a station and let them begin the taste tests. Watch closely to see that directions are being followed, and answer any procedural questions that may arise.
When each team has finished at its first station and filled out its datasheet completely, place a new datasheet at each station and make sure the box containing the food is covered with the fabric. Then have the teams rotate in one direction to the next nearest tasting station. There, they choose a new presenter and timer, and divide the remainder of the team into “smelling” and “non-smelling” halves, as they did for the first station. Then they conduct the taste tests and record their data.
Repeat this procedure for the third and fourth tasting stations. Remind students to keep their voices as quiet as possible, and not share their food identifications with other teams as they rotate to new stations. If necessary, explain that giving away a food type or flavor would ruin the fun—and make the experiment invalid.

Part 2: Graphing and interpreting the data

Once the tasting experiment has been completed, announce or write on the classroom board the foods and flavors for each of the four tasting stations. Then have each team look over its four datasheets. What do students notice about the data? Were students more successful at identifying the foods when they could smell them? If so, was there a big difference in the number of correct responses between the able-to-smell versus not-able-to-smell groups? Were the foods at some stations more difficult to identify, based on the number of incorrect responses, than the foods at other stations? If so, was this consistent across all the teams?
Explain to the class that bar graphs let us see at a glance the answers to these questions. Give each person a sheet of graph paper, and show the class how to set up the axes to make a bar graph of the results for the first tasting station. Make the graph consist of two pairs of vertical bars. The first pair shows the results of the able-to-smell tasters. Within that pair, the first bar shows the number of correct responses, and second shows the number of incorrect responses. The second pair of bars shows the results of the not-able-to-smell tasters. Again, the first bar shows the number of correct responses, and second shows the number of incorrect responses. Then have students choose a crayon or marker color to fill in both of the correct-responses bars, and a second color for the incorrect response bars. The use of colors means that they need to add a legend to the graph indicating what the colors represent. Be sure to ask why using the two different colors in the graph is a good idea. Expect students to respond that colors help to make any differences in the successes of the two different tasting groups more noticeable.
If students have not already done so, make sure that their y-axis is labeled appropriately, such as “number of tasters,” and the x-axis includes labels beneath each pair of bars indicating whether they represent the able-to-smell responses or the not-able-to-smell responses. Also point out that all graphs need informative titles. Ask the class to come up with one. Examples, ones that are fairly specific, might be: “Results from Food Tasting Experiments” or “Food Taste Experiments With and Without Smell.” Next, point out that the graphs need to indicate the station number, the source of the data. Include this information as part of the title or as a separate label elsewhere.
Once students have completed their graphs for the first tasting station, provide more graph paper and have them construct similar graphs for each of the other three stations. As they are working, circulate through the room and ask what they think their graphs show about people’s ability to taste foods under different circumstances.
When teams have finished the four graphs, have each team combine the results for all four stations. In other words, ask students to determine the total number of correct responses from all the able-to-smell tastings that occurred in their team, and the total number of correct responses from the not-able-to-smell tastings that occurred. Then have them do the same for the incorrect responses, and have them graph these results on a new sheet of data paper. Expect the bars on these graphs to be much higher than on the previous graphs.
By now, each student willl have completed five graphs. From each team, choose (or have the team choose) one graph from each of the five types. Tape them to the classroom board or mount them on a bulletin board so that results of each station are all together in one spot, and the combined results (the last graphs made) are together. At this point, any similarities and differences between the teams’ results become apparent, so ask students to point these out to you. If any noticeable differences exist between teams, ask why they think these might have occurred. Finally, ask students what they conclude about whether or not smell is important to the ability to recognize and identify foods, and ask whether or not their hypothesis was supported.

Part 3: Relating the experiment to human adaptations

Ask students what they remember from the earlier discussion about the adaptive value of being able to recognize and remember whether certain things are good to eat, that is, nutritious, or bad to eat, that is, noxious. Students may be interested to know that when babies are just starting to eat soft foods (after a few months of drinking only milk), they behave much the same way our early ancestors probably did when finding a strange berry or unknown root. They knew from experience that some things that looked like edible might instead make them sick, so they would only take a small sample at first. If they did not get sick after several hours, they would then eat a larger quantity —and of course, remember what it looked and tasted like for future reference. Similarly, infants refuse to eat more that a bite or two of a food they have not tasted before, even though the parent knows that it is a safe and healthy food. The second time the infant is offered the food, it will eat a little more. After that, it will be willing to eat full portions. This cautious behavior when experiencing new foods seems to be instinctive (one we are born with) in humans.

After this brief discussion of adaptive behavior, ask the class a harder question: what is the difference between the sense of taste and the sense of smell? Give them some time to share their opinions, and then draw a map of the tongue’s upper surface on the board, showing the regions that respond to the sweet, salty, sour, and bitter aspects of food. Then ask the class how the tongue can distinguish between different flavors of pudding, which are all sweet, if it has only the ability to distinguish between, say, sweet versus salty foods? Since it can’t, explain how the sense of smell works, especially as it relates to eating. Finally, conclude the activity and lesson by pointing out that not only is food tasting behavior adaptive, but the structures that allow us to taste foods—which includes smell—are adaptations of the body that have helped humans survive for thousands of years.

Safety Issues

  • Check for food allergies well in advance of the activity. Since the quantity of dairy products involved in the tasting experiment is extremely small, this should not be a problem for students with lactose intolerances. Nevertheless, consult with parents if you do have lactose-intolerant students in the class. If you are advised not to allow them to participate, substitute pureed fruit baby food products for the experiment.
  • Make sure all surfaces in the tasting areas are scrupulously clean before beginning.
  • All students should wash their hands thoroughly before and after serving as “feeders.” You may provide bottles of liquid hand-sanitizer at each station as an alternative, but be sure to check that students use them in such as way as to be effective.

Troubleshooting Tips

  • Make sure that students state their food identification responses before they release their noses for the not-able-to-smell components of the tastings. Responses given after releasing their noses should not be counted as correct responses, but instead should be marked on the datasheets as “none.”
  • Demonstrate the correct amount of food (about one-half to three-quarters of a teaspoon) that feeders should put on the spoon; if they use too much it may slide off the spoon before it reaches the taster’s mouth, or the food may run out before the end of the experiment.
  • Remind students not to share information about what a food is with students who have not yet had an opportunity to taste it.
  • Emphasize that the point of the experiment is not to get the food answers “right,” but to find out if it is harder to tell what a food is if you can’t smell it. Then ask if this information about the sense of smell is consistent with the results they got in their experiment. To use a pun, does it make sense that food identification is difficult or impossible without the sense of smell?

Investigating Questions

As students are conducting the experiment, ask the following questions:
  • What do you notice about the responses so far?
  • Are students more successful at identifying the foods when they can smell them? If so, is there a big difference in the number of correct responses between the able-to-smell versus not-able-to-smell groups, or is it only a small difference?
  • So far, does it look like your hypothesis is going to be supported?
  • Do the foods at some stations seem more difficult to identify than the foods at other stations? If so, why do you think that might be?
At the end of the concluding discussion, ask:
  • Why do many people complain that when they have a bad cold that food seems to lose its taste?

Assessment

Example quiz or discussion questions:
  • A fellow student tells you that he is going to give you either a piece of a plain brownie, or a piece of a brownie containing walnuts, but you have to close your eyes and hold your nose while you chew and swallow it. If you can correctly identify which piece he has given you, he will then give you the rest of the brownie. Do you think you will be able to correctly identify which piece he has given you? Why do you think that?
  • Another student tells you that she is going to give you either a spoonful of cherry Jello® or a spoonful of orange Jello®. However, if you want more than a spoonful, you will have to close your eyes and hold your nose while you eat it, and then correctly identify the flavor. Do you think you will be able to do it? Why do you think that?
  • Why do some people think that food has less flavor when they have a stuffy nose from a bad cold?
  • Create a bar graph similar to the ones students created, but showing the results of a different experiment, such as the one shown in the attachment test-graph.gif. Then ask the following questions:
  1. What was the total number of correct answers given by students who studied for the spelling test?
  2. What was the total number of incorrect answers given by students who studied for the spelling test?
  3. What was the total number of correct answers given by students who did not study for the spelling test?
  4. What was the total number of incorrect answers given by students who did not study for the spelling test?
  5. What can you conclude from this experiment?
  6. What hypothesis do you think this experiment was testing?

Activity Extensions

Many elderly people complain that food is not as flavorful to them as it was in their younger years. Have students do some library and/or internet research to try to find out if indeed this is reported to happen, and if so, why it happens. They could also survey older people, asking them if they find food less flavorful than it was when they were younger. Also, see if you can locate a dozen or more elderly volunteers (perhaps grandparents of students) willing to visit the classroom. They can serve as the tasters for the same experiment that students performed on themselves, and students can compare results from the elderly group to their own results. This time students would be testing the hypothesis, “Elderly people will not be able to identify food as well as fourth-graders can.”
Additional Resources
  • Flavor Chemistry. ChemMatters video on the science behind the taste and smell of food [YouTube 5:05]

References

Hebrank, M.R., 1995. “An Exercise in Good Taste,” in Biology on a Shoestring, National Association of Biology Teachers, Reston, VA.

Contributors

Mary R. Hebrank, project and lesson/activity consultant

Copyright © 2013 by Regents of the University of Colorado; original © 2004 Duke University

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