National Agricultural Literacy Curriculum Matrix
Mystery Juice (6-8th Grade)
6 - 8
Three 45-minute class periods
Using an inquiry approach, students will develop an investigation to determine the difference between two juices. Food safety will be discussed in relation to the results of the investigations. Students will have the opportunity to discover how pasteurization reduces the number of microorganisms in a food such as juice.
For the Class
- Pasteurized and unpasteurized juice (1 to 2 cups of each) in clear containers
For Each Team
- 2 to 4 sterile Petri dishes with nutrient agar and covers
- Sterile swabs
- Parafilm to seal dishes
- Safety gloves
- Do some juice “scouting” and find pasteurized and unpasteurized juice made from the same type of fruit. (If available, unpasteurized apple cider and pasteurized apple juice work well.)
- If unpasteurized juice is not available, you can prepare your own (see below).
- Use 2 pint jars or other clear containers that have lids. Wash and sterilize the jars and lids (see page 8).
- Mark one container “A,” and pour in 1 to 2 cups of the unpasteurized juice. Close the lid.
- Mark the other container “B,” and pour in 1 to 2 cups of the pasteurized juice. Close the lid.
- Keep the containers closed and refrigerated until class time.
- On activity day, place the equipment that students might use on a lab table.
irradiation: the process in which ionizing energy is used to kill foodborne pathogens
pasteurize: a process of partial sterilization involving heat treatment to kill bacteria and make a product safe for consumption and to improve its keeping quality
Did you know? (Ag Facts)
- More than 1,000 different types of food are pasteurized.
Background Agricultural Connections
Interest Approach – Engagement
- Set the stage for the activity by saying to the class: I have a mystery for you to solve. Together, we’re going to do some sleuthing! Here are two containers of juice.
- Do you see any differences between them? Remember, all science begins with awareness. What’s one way we become aware? (By making observations)
- How do we make observations? (Through the use of our senses. Mostly, we use sight. But sound, taste [although not in this case], and touch are also ways to make observations.)
- Can you determine which juice is safe to drink just by looking? Today, we’re going to do some detective work, and plan and carry out an investigation. Then you’ll report your findings to the class. It will be challenging! Let’s get started ...
1- Design the Lab
- Assign students to work in teams of 3 or 4.
- Ask each team to record at least 5 observations about the juice. (Students may notice color and clarity differences. One juice may have some solids in it, etc.) You may wish to help them understand the difference between observation and inference before they start.
- Ask each team to share their best observations with the class. List them on the board.
- Ask the students what the different observations may mean.
Develop a Hypothesis
- Develop a Hypothesis: Based on the class observations, challenge each team to come up with a hypothesis of which juice is pasteurized and which one is unpasteurized, and have them explain their reasoning.
Solve The Mystery
- Now ask the students to solve the second part of the mystery by asking, "Which juice is safe to drink … and why?"
- Ask each team to design a lab to provide evidence for which juice is safe to drink. You may want to review pasteurization with the students. Students can use materials and equipment on the lab table.
- Challenge students to develop their experimental designs complete with a control (in this case, a standard of comparison).
- If your students come up with a variety of ways to determine which juice is safer to drink (pasteurized), that’s great. Go for it!
2-Conduct the Lab
Option: Students can design a data table to record their results.
- Ask the students to review their experimental designs.
- Have teams carry out their labs.
- Note: You may need to show the students how to dip the sterile cotton swab into the juice and then inoculate the dishes (see page 2 of the Safety First in the Lab handout.)
3-Collect, Organize, and Report Results
- Have teams observe the results of their lab and report their results to the class.
- Note: The unpasteurized juice should have a greater number of colonies when samples of both juices are plated on agar dishes.
- Together with the students, analyze the adequacy of the experimental designs. Ask students what they would do to improve their labs.
- Ask the students to relate their findings to food safety.
- Review how the students used the various pieces of equipment and how they designed their labs, complete with controls.
Concept Elaboration and Evaluation
- Which juice would you prefer to drink, pasteurized or unpasteurized? Why?
- What effect would freezing have on microorganisms in unpasteurized juice? (Freezing does not kill bacteria. It only slows their growth.)
- How does pasteurization relate to your everyday life? (It keeps your food safe.)
- Can you tell if a food is pasteurized by looking at it? (No — you must read the product labels.)
Pasteurization is the process of destroying microorganisms that can cause disease. This is usually done by applying heat to a food. In order to determine which mystery juice is pasteurized, both must be plated on agar dishes and observed. The unpasteurized juice should have a greater number of organisms because it was freshly squeezed and may be contaminated from handling, etc. It hasn’t been heated to destroy bacteria.
We welcome your feedback! Please take a minute to tell us how to make this lesson better or to give us a few gold stars!
Research the history of pasteurization.
Research why some milk can be stored on the shelf and some milk must be refrigerated.
Write a letter to Louis Pasteur to thank him for developing the process of pasteurization, and tell him how important this process is in lowering the incidence of foodborne illness. Also explain how it makes foods more convenient for us today.
Answer the question raised in the video by Dr. Sizer, “How can you pasteurize an egg in the shell without cooking it?”
Research how people safely stored food prior to pasteurization, and choose which method you think was best — give reasons, specific details, anecdotes, and examples.
Suggested Companion Resources
- Beef Blasters (Activity)
- The 12 Most Unwanted Bacteria (Activity)
- Louis Pasteur and Pasteurization (Book)
- Animated Life: Seeing the Invisible (Multimedia)
- How Safe is Your Salad? (Multimedia)
- Food Safety A to Z Reference Guide (Website)
Agricultural Literacy Outcomes
Food, Health, and Lifestyle
- Explain the benefits and disadvantages of food processing (T3.6-8.e)
- Identify forms and sources of food contamination relative to personal health and safety (T3.6-8.h)
Science, Technology, Engineering & Math
- Explain the harmful and beneficial impacts of various organisms related to agricultural production and processing (e.g., harmful bacteria/beneficial bacteria, harmful/beneficial insects) and the technology developed to influence these organisms (T4.6-8.f)
Education Content Standards
Food Products and Processing Systems Career Pathway
FPP.01.02Apply food safety and sanitation procedures in the handling and processing of food products to ensure food quality.
FPP.01.03Apply food safety procedures when storing food products to ensure food quality.
FPP.03.03Create food distribution plans and procedures to ensure safe delivery of food products.
Health Standard 5: Demonstrate the ability to use decision-making skills to enhance health.
5.8.4Distinguish between healthy and unhealthy alternatives to health-related issues or problems.
Common Core Connections
Speaking and Listening: Anchor Standards
CCSS.ELA-LITERACY.CCRA.SL.1Prepare for and participate effectively in a range of conversations and collaborations with diverse partners, building on others’ ideas and expressing their own clearly and persuasively.
CCSS.ELA-LITERACY.CCRA.SL.2Integrate and evaluate information presented in diverse media and formats, including visually, quantitatively, and orally.