Make Homemade Yogurt

Learning how to make homemade yogurt is not only fun, it can also be a great food science experiment. With just milk, plain yogurt, and warmth, kids can observe how live bacteria transform milk into a thick, tangy food.

This activity is part of our Food Science Experiments for Kids collection where you can explore kitchen chemistry, growing experiments, and edible science projects.

Since yogurt takes several hours to sit, a good time to start is around 1 or 2 p.m. That way it can rest overnight and be ready to stir the next morning.

What You Need

• 4 cups milk
• 1/4 cup plain yogurt with live active cultures
• Small 2-quart crockpot
• Bowl
• Whisk
• Large blanket or towels
• Plastic container for storage

How to Make It

Step 1: Heat the Milk

Use a small 2-quart crockpot, turn it to low, and pour in 4 cups of milk.

Step 2: Warm the Milk

Cover with the lid and cook on low for 3 hours.

Step 3: Let It Rest

Turn off the heat and let the milk sit in the covered crockpot for 3 hours.

Step 4: Remove Some Milk

After 3 hours, take out 1 cup of the warm milk and place it in a bowl.

Step 5: Add the Yogurt Starter

To the 1 cup of warm milk, add 1/4 cup of plain yogurt. Whisk together until smooth.

Step 6: Return the Mixture

Pour the yogurt and milk mixture back into the crockpot and whisk together.

Step 7: Keep It Warm Overnight

Cover the crockpot with a large blanket or towels and let it sit overnight.

By covering your crockpot, you are making an incubator.

Step 8: Stir and Chill

The next day, whisk the yogurt and place it in a plastic container. Store it in the refrigerator.

Use within 1 week to 10 days. If you would like to make it again, save 1/4 cup of your yogurt for the next batch.

---

---

What Happens?

The ready-made yogurt has live bacteria in it. When those bacteria are combined with warm milk and kept in a warm place, they begin to grow and ferment the milk. As fermentation continues, the milk thickens and develops the tangy flavor we expect from yogurt.

Why It Matters in Cooking

This experiment shows kids that some foods are made by helpful bacteria. Homemade yogurt is a great example of food science in everyday cooking. It teaches that temperature, time, and live cultures can completely change an ingredient.

• Kids learn how fermentation changes food
• They see why warmth matters in food science
• They understand how one food can help make another
• They connect science to something they can actually eat and use

Questions to Ask Kids

• What changed about the milk after it sat overnight?
• Why do you think the crockpot had to stay warm?
• What role did the plain yogurt play?
• How was the texture different before and after?
• Why is this considered fermentation?

Ways to Extend the Experiment

• Compare homemade yogurt with store-bought yogurt.
• Try adding fruit after the yogurt is finished.
• Record how thick the yogurt becomes after different resting times.
• Use part of your finished yogurt to start another batch.

Safety Tips

• Adult help is needed when using the crockpot.
• Use clean bowls, whisks, and containers.
• Refrigerate the yogurt after it has incubated.
• Do not keep yogurt past the recommended storage time.

Use Your Homemade Yogurt In

You can make a larger batch if you know you will be able to use the yogurt within a week.

Homemade Yogurt Maker

Try These Kitchen Science Experiments Next

If you enjoyed this homemade yogurt activity, try these other fun food science experiments.