Microbes on My Mind: Lesson 3

Opening Questions

• How do you think yogurt is made?
• Where do you think the concept of making yogurt originated from?
• Describe the texture and taste of your yogurt.
• How do you think different flavors of yogurt are made?

Part 1: Let’s Do It!

1. Give participants a small cup with yogurt and allow them to place toppings of their choice on it.
2. Provide each participant with one copy of the Microbes in Our Food Introduction and Lab Analysis worksheets.
3. When all participants have their samples and are enjoying their treat, ask the Opening Questions.
   • How do you think yogurt is made?
   • Where do you think the concept of making yogurt originated?
   • Describe the texture and taste of your yogurt.
   • How do you think different flavors of yogurt are made?
4. Direct participants to take notes from the class discussion for each question on the worksheet.
5. Engage participants’ questions/responses about the production of yogurt. Ask participants to come up with a list of ideas they have about what is required to make yogurt.
6. Show participants the presentation on how yogurt is made and the importance of fermentation. Direct them to fill in the missing words on their worksheets.
7. Show participants any items or pictures of different items that go through the fermentation process (bread, sauerkraut, soy sauce, etc.) that you brought in and discuss with participants the importance of fermentation and bacteria in food production.
8. Direct participants to join their small groups.

Facilitator Lab Procedure

This first part of the activity will be conducted by the facilitator. It is highly suggested participants watch this procedure being done. This gives the facilitator a chance to discuss why it is important for the mixture to be heated before the production of yogurt. (Bacteria thrive in warm and wet environments, and we want the bacteria in the yogurt to grow.) This is also an opportunity for the facilitator to discuss why certain foods have to be cooked before consumption. This connects to the food safety aspect of this lesson.

The following mixture will make enough for 4 groups. Double the amounts as needed for more groups.

1. Plug in the hot plate and set to medium-high.
2. Add 3-3 1/2 cups whole milk to a large beaker or saucepan and place it on the hot plate.
3. Add 3/4 cup of powdered milk into the liquid milk.
4. Stir the mixture slowly and constantly.
5. Use the cooking thermometer to monitor the temperature of the milk.
6. When milk gets between 175-200ºF, remove from heat. (Note: yogurt will not set up properly if the milk boils.)
7. Cover the top of the milk with plastic wrap to prevent a film from developing on top of the substance.
8. Allow the milk to cool to approximately 135ºF.
9. Once the milk has reached the desired temperature, remove the plastic wrap.
10. Dispense the milk into four foam cups (one cup per group).

Participant Lab Procedure: Part 1

Participants will need to have all materials listed on the Lab Procedure at their workstations.

1. Label the bag using a permanent marker with group members’ names.
2. Use the spoon to mix the milk to make sure nothing has started to settle.
3. Add one teaspoon of yogurt starter into the cup.
4. Stir the mixture carefully but make sure the starter gets evenly distributed throughout the milk.
5. Once the solution is completely mixed, cover the cup with plastic wrap.
6. Place the plastic lid on top of the cup over the plastic wrap.
7. Carefully place the cup down into the sealable bag.
8.  Take the newspaper provided and rip it into shreds. Place the newspaper shreds around the cup in the bag to help retain heat.
9. Make sure the bag is tightly sealed. The top of the bag may also be taped to help prevent spills.
10. Place the yogurt mixture into an insulated container for 6 hours or longer (overnight is acceptable).