Introduction to Flavor Chemistry Mark as Favorite (9 Favorites)

LESSON PLAN in Observations, History, Identifying an Unknown, Molecular Structure , Functional Groups, ACS National Historic Chemical Landmarks Program. Last updated January 30, 2024.


Summary

In this lesson, students will read an article about flavor chemistry to learn about the science of tasting. There are a series of activities to help promote literacy in the science classroom related to the reading and help students experience what they’ve read about. One part, the Job Interview, could be used as plans for a substitute teacher since the activity is self-guided.

Grade Level

High School

NGSS Alignment

This lesson will help prepare your students to meet the performance expectations in the following standards:

  • HS-PS2-6: Communicate scientific and technical information about why the molecular level structure is important in the functioning of designed materials.
  • Scientific and Engineering Practices:
    • Asking Questions and Defining Problems
    • Using Mathematics and Computational Thinking
    • Analyzing and Interpreting Data
    • Obtaining, Evaluating, and Communicating Information

Objectives

By the end of this lesson, students should be able to:

  • Explain that flavor is an experience of both taste and smell.
  • Different people taste flavors differently due to the number of papillae.
  • Identify the four basic tastes: sweet, salty, bitter, and sour.
  • Obtain, evaluate, and communicate information about a specific flavor molecule.

Chemistry Topics

This lesson supports students’ understanding of:

  • Organic Chemistry
  • Molecular Structure
  • Functional Groups
  • History
  • Identifying Unknowns

Time

Teacher Preparation:

  • What Kind of Taster Am I?: 15 minutes
  • Taste Recognition: 20 minutes
  • Job Interview: 10 minutes

Lesson: Approximate times for students to complete each activity in the lesson:

  • Anticipation Guide: 5–10 minutes
  • Reading: 20 minutes
  • What Kind of Taster Am I?: 45 minutes
  • Taste Recognition: 30 minutes
  • Job Interview: 2 hours

Materials

  • What Kind of Taster Am I? (per group)
    • Droppers with blue or green food dye
    • Magnifying glass
    • Wax paper squares cut to be a frame, measuring 1 square centimeter (1 per student)
    • Scissors
    • Flashlight
    • Camera (optional)
    • Soap
    • Water (for swishing mouth)
    • Gloves
  • Taste Recognition
    • Citric acid solution (0.5 g citric acid + 999.50 g water)
      • * Must be food grade
    • Sucrose solution (7.00 g sucrose + 993.00 g water)
    • Salt solution (1.00 g + 999.00 g water)
    • Tonic water (flat)
    • 7 L of water
    • 6 small disposable sample cups per student
    • Sharpie marker and/or labels to label cups
    • 5 1-L measuring cups (or larger) to make solutions
    • Paper ballots (see student resource)
  • Job Interview
    • Computers with internet connection

Safety

  • Food and drink are not permitted in the laboratory; be sure to complete this activity in a non-lab setting.
  • Wash your hands with soap and water before you begin.
  • Wear gloves at all times.
  • Be sure that the tip of the dropper does not come into contact with your partner.
  • Do not consume any solution from laboratory glassware.

Teacher Notes

Background:

Lesson Overview:

The lesson includes multiple components as outlined individually below. The Reading is essential for all of the activities. Teachers can choose to do one or all of the included activities. Student handouts and corresponding answer keys are provided for each item described below:

  • Activity: Anticipation Guide
    • Anticipation guides help engage students by activating prior knowledge and stimulating student interest before reading. If class time permits, discuss students’ responses to each statement before reading the article. Then, while they read, students should look for evidence supporting or refuting their initial responses.
  • Reading: Flavor Chemistry at the USDA
  • Activity: What Kind of Taster Am I?
    • Students determine the number of papillae they have within a 1cm2 defined area to determine what type of a taster they are (non-taster, average taster or supertaster).
    • Either the students or teacher can prepare the wax paper square “frames” needed for the activity. This should be a piece of wax paper cut out like a frame, with the open portion measuring 1cm x 1cm.
    • Students will be instructed to drop food coloring on their tongues. The dye should last less than a full day, typically only a couple of hours. Teeth may get colored too. As an alternative, students could eat frosting that has been dyed blue and it would achieve the same effect of being able to see the papillae on their tongue.
    • Note that students may find the food coloring bitter.
    • Remind students not to let the food coloring dropper hit their lips, teeth, tongue, or mouth.
    • Everyone needs to wear gloves and wash their hands before and after the activity.
    • Droppers need to be new at the time of the lab and not previously used for other lab work to avoid cross-contamination. They could be sanitized between use or if they happen to touch a student's tongue.
    • This activity should not take place in a lab setting. Ensure that cups and drinkable water are available for use in this activity.
  • Activity: Taste Recognition
    • Students taste different unknown solutions to see if they can identify the kind of taste each is (salty, bitter, sweet, or sour).
    • Solution preparation measurements are included in the materials section.
    • Prior to the class period, prepare 5 1-L samples: one with each of the four flavors (salty, sweet, bitter, and sweet) and one with plain water.
    • Students will need five tasting cups plus one cup for water. All water and the blank should come from the same water source.
    • Make sure that there is a place (like a sink) available for students to spit out the solution after they have tasted it.
    • Use a random four-digit code for each solution (examples provided on the student handout), so students cannot share answers among sections.
    • It is suggested that the tonic water is allowed to go flat in order to create a good comparison to the other substances.
    • The taste recognition for each sample should follow:
      • Citric acid: sour
      • Sugar water: sweet
      • Salt water: salty
      • Tonic water: bitter
    • Data/outcomes will vary; some students may be able to recognize all four flavors, others may be able to recognize one or no flavor. This is due to differences in the number of papillae, thus the different types of “tasters.”
    • An extension option: Try this at different temperatures (warm, cold, room temp) to determine whether temperature affects the ability to taste different flavors.
    • Be sure that this activity is not completed in a lab setting.
  • Activity: Job Interview
    • Students are on a career journey to become a flavorist, or a flavor chemist. You could share this career profile with them. To become a flavorist, a person must go through a multistep process. Usually, this process starts by obtaining a chemistry degree, studying with a flavorist, and then demonstrating knowledge for the Society of Flavor Chemists. As part of this test, the applicant must identify the major chemical components that characterize flavors and aromas of natural flavoring.
    • Students will work independently or in pairs. They should choose (or be assigned) a flavor and research the major compounds that give each taste its flavor and choose a way to communicate their research findings.
    • Part of the research is comparing molecules with other teams. To be successful with this activity, students should be familiar with the terms and concepts listed below. Many of the flavor compounds contain these properties. This could be a good introduction into organic compounds/topics:
      • Isomers
      • Structural isomers
      • Stereoisomers
      • Enantiomers
      • Cis/trans isomers
      • Lewis structures
      • Functional groups such as alcohols, esters, aldehydes, carboxylic acids
    • A list of the natural flavoring items (found in the syllabus for the Society of Flavor Chemists) is available for download and can be used as an answer key for the research portion of this activity.
    • A suggested grading rubric can be found in the answer key document.