Make your own yoghurt

Make your own yoghurt

Another tasty science treat

Yoghurt is made using bacteria which are good for us. Have a look at The Invisible Helpers to find out more about these bacteria. You can make your own yoghurt at home!

What you need:

  • 2 litres of milk (skimmed or semi-skimmed)
  • 100 g (1/2 cup) dried milk powder (optional)
  • 8 tbsp (1/2 cup) plain, live yoghurt
  • Saucepan
  • Mixing bowl
  • Hand whisk
  • Thermos flask / cling film and clean towel
  • Sterile air tight container e.g. jam jar, coffee jar

How to:

Have a look at this video which shows you how to make your own yoghurt:

  1. Put the milk in a saucepan and place over a medium heat. Heat the milk to 80 degrees Celsius. If you don't have a thermometer, wait until the milk steams and bubbles appear around the edge.
  2. Pour into a mixing bowl and leave to cool until the milk reaches 46 degrees Celsius.
  3. Whisk in the yoghurt and dried milk powder. Dried milk powder thickens the yoghurt, so if you want runnier yoghurt, use less milk powder.
  4. In the video, the yoghurt is poured into glass jars and put in an oven with the light on overnight. Alternatively, you can cover the top of the mixing bowl with cling film and a clean towel and leave the bowel somewhere warm - in an airing cupboard or on top of a radiator. Another option is to gently warm a thermos flask and pour the mixture in there.
  5. Leave the mixture for 6-8 hours or overnight.
  6. If the yoghurt has thickened and looks set, pour it into a sterile, airtight container and put it in the fridge.

What's happening?

Heating the milk pasteurises it. This kills off any bacteria that might compete with your yoghurt-making bacteria. You need to cool the milky slightly before adding the yoghurt-making bacteria, as high temperatures would kill them too!

Yoghurt is made by adding the bacteria Streptococcus thermophilus and Lactobacillus bulgaricus into heated milk. These bacteria aren't harmful to humans. The bacteria feed on the lactose in the milk and produce lactic acid as a by-product - this is a type of fermentation. The lactic acid causes the milk to coagulate and thicken. You've made yoghurt!

Curriculum information