Makin’ Yogurt

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Makin’ Yogurt

Two species of bacteria, Lactobacillus bulgaricus and Streptococcus thermophilus, grow in a symbiotic relationship and are used in starter cultures in the manufacture of yogurt. You can make your own yogurt with this overnight project.

For a printable version of this project, click here.

Materials

• Saucepan
• Cooking thermometer
• Clear plastic or glass cup
• Plastic wrap
• Foam cooler
• 1 2 Litre pop bottle
• pH paper
• Ice bath (bowl filled with ice and water)
• 1.25 g yogurt starter culture (available at nutrition or other specialty food stores)
• 1 g gelatine (e.g. Knox)
• 1 cup whole milk
• Jam (for flavouring)

Note: These ingredients make one serving. To make a larger amount, adjust the ingredients proportionately.

Instructions

1. Add gelatine to milk in a saucepan.
2. Stirring continuously, heat to 82°C. Don’t burn yourself—ask an adult for help!
3. Cool to 40°C in an ice bath.
4. Add the starter culture and stir.
5. Transfer the milk products into a clear plastic or glass cup and cover with plastic wrap.
Makin' Yogurt Instructions

6. Incubate the milk products at 40°C overnight until gels have formed and then refrigerate. To incubate, you can simply put the container in a foam cooler overnight along with a 2 L pop bottle filled with really hot water.
7. Use a strip of pH paper to measure the pH level. It should be about 4. (If the pH is not 4, you should start over with fresh ingredients.)
8. Add jam or preserves to taste.