Make Homemade Yogurt

Learning how to make homemade yogurt is not only fun, it can also be a great kitchen science experiment. With just milk, plain yogurt, and warmth, kids can watch 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.

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What Happens When You Make Homemade Yogurt?

Warm milk mixed with plain yogurt creates the right environment for live bacteria to grow. As the bacteria multiply, they ferment the milk sugars and thicken the milk into yogurt.

• Milk is heated
• The milk cools slightly
• Plain yogurt is stirred in
• The mixture stays warm overnight
• The milk thickens into yogurt

Result: A smooth, tangy yogurt made by fermentation.

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

Make It Homemade

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.

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Use Your Homemade Yogurt In

Smoothies
Parfaits
Stir into mashed potatoes
Yogurt Soup
With granola
Pancakes
Fruit Dip
Greek Gyros with sauce
Frozen Yogurt Snacks
Frozen Yogurt
Yogurt Bites
Yogurt Cups

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

Homemade Yogurt Maker

Science Behind Homemade Yogurt

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.

The tangy flavor comes from this fermentation process. Simply put, yogurt is milk that has fermented. You cannot make yogurt without these active bacteria cultures.

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.

Homemade Yogurt FAQ

Why does homemade yogurt need warmth?

The live bacteria in the yogurt need a warm environment to grow and ferment the milk.

What does the plain yogurt do in this experiment?

The plain yogurt provides the live active cultures that start the fermentation process.

How long does homemade yogurt take to make?

This method takes about 18 hours total, including warming, resting, overnight incubation, and chilling.

Can you use homemade yogurt to start another batch?

Yes. Save about 1/4 cup of your finished yogurt to use as the starter for the next batch.

Try These Kitchen Science Experiments Next

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

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