Science and Our Food Supply: Investigating Food Safety from Farm to Table

ADVANCE PREPARATION

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You may want to send home a note to explain why 

you’re asking students to bring in items from their  

kitchens. 

• 

Bring in 1-gallon, sealable (zipper-style) plastic bags, at 

least one for each student.  

• 

Bring in extra kitchen items for students who aren’t able 

to bring items from home. 

• 

Make one copy of the Lab Report Outline for each  

student (page 23). 

MODULE 4:

 RETAIL AND HOME

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MIDDLE LEVEL

CROSSED UP! 

INTRODUCTION

Explain to students: Bacteria are everywhere, including in your very own kitchen! In this lab, you’re going to 

become kitchen inspectors and look in your kitchens for things that may contain bacteria. 

PROCEDURE

1

LAB:

 INTRODUCE THE LAB  

Ask students: 

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Where in your kitchen could bacteria be growing? 

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Could bacteria be on the kitchen items that you or your 

parents use when preparing food? Make a list of students’ 

responses. 

Some Probable Answers: 

–  Sponges 

–  Dishcloths 

–  Dish towels 

–  Pot scrubbers 

–  Vegetable brushes 

–  Can-opener blades 

–  Sink stoppers or  

disposal covers 

–  Paper towels 

–  Utensils 

–  Cutting boards 

–  Dishes 

• 

Next, ask students to hypothesize about which kitchen 

items contain the most bacteria and which contain the 

least bacteria. Make 2 lists: “Most Bac” and “Least Bac.” 

Ask them: Why would/wouldn’t bacteria be found on 

these items? 

• 

Then ask students to vote on the items most and least 

likely to harbor bacteria. List the Top 5 items in each  

category. Keep the Top 5 lists on the board through the 

next few labs so students can compare their lab results 

with the lists. 

• 

Group students into teams of 3 to 4. Ask each team to 

choose at least 3 or 4 kitchen items they want to inspect. 

–  Students should include items they think will have lots 

of bacteria as well as those they think will have fewer 

bacteria. For example, they may want to compare  

new sponges or just-washed dishcloths with dirty or 

just-used sponges or dishcloths. 

–  Items don’t have to be chosen only from the class list. 

Teams can pick their own items to investigate. Try for 

as many different items as possible but make sure the 

important ones, such as sponges, dishcloths and dish 

towels, are included by at least 2 teams.  

• 

Give each team 1-gallon storage bags to take home. Ask 

them to bring in kitchen items from home to test. Remind 

students to ask their parents’ permission to bring the 

items to class. Ask them to put in 1 item per bag, seal the 

bag, and bring it to class. Mention that they should bring 

in some items, like dishcloths, “as is” rather than washing 

them first. 

Note: This lab should be set up to avoid any comparing and 

critiquing of items from students’ homes. Put a number 

on each bag as students give the bags to you. Write each 

student’s name on a list with their corresponding bag 

number. The lab should be a general learning experience 

about how to avoid cross-contamination in the kitchen, not 

a specific review of individual items. For example, students 

should look for common items that are most likely to harbor 

bacteria. 

 MODULE 4:

 RETAIL AND HOME

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