In December we were staying in Germany for Christmas and during that time we had a discussion with my parents about Finnish joghurt. If you were ever used to German joghurt you will only like some of the Finnish joghurts, perhaps the one liter fruit joghurt or the Turkish/Greek style joghurt. Everything else is just too watery or very tasteless from a German perspective. During the discussion someone suggested that we should make joghurt on your own. We looked it up on some websites and books, read some recipes and blogs and then started.

The microorganisms, mostly lactobacili I guess, in the starter (fresh joghurt from the shelf) have a certain temperature range where they live and grow. As the bought joghurt didn't list which exact microorganisms were used we guessed a temperature somewhere between 40°C to 45°C would be optimal. We also wanted to denature milk proteins, which happens from 65 to 95°C in order to prevent forming of curds. As we didn't have a thermometer around I used one of the DS18B20, which I use for monitoring the water line in winter, and an Arduino to measure the temperature of the milk.

Step by Step

  1. Heating up the milk to 85°C and keeping it there for 5 to 10 minutes - don't bringt it to boil
  2. In the meantime getting the glasses we are going to fill sterile as we use them for the first time - water bath at about 100°C (visibly boiling)
  3. Letting the milk cool down to 45°C - could be speeded up using a cold water bath
  4. Filling some starter into the glasses - 1 tea spoon per glass
  5. Filling the 45°C milk into the prepped glassed
  6. Storing the glasses in an insulation box in a warm place for about 6 hours
  7. Storing them in the fridge
  8. Enjoying the product!