Soy yoghurt is not identical to dairy yoghurt, but it works well in cooking. As a starter, you may use soy or any plant based yoghurt, if you can get it commercially. If not, use dairy yoghurt or rejuvelac to start. This is just to introduce the right bacteria for the culture. Once you have your own soy yoghurt, don’t forget to freeze a little to use as a starter, so that you will never be without it.
Bring the soy milk to 42-45°C. The culture will only thrive in a narrow temperature range: too cool and it won’t be active, too hot and it will die. It should be the same temperature as baby’s milk. Add the starter to the soy milk and mix well with a sterile spoon. Do not stir or move the container until the yoghurt sets – in about 8-10 hours. Transfer to the refrigerator.
Making the Soy Yoghurt Thicker
You will notice that home made yoghurt will be a little runnier than dairy yoghurt. To improve the thickness of the soy yoghurt, you could add one level teaspoon of agar powder, which is premixed in 50 ml water, to the soy milk when it begins to boil. You could also use corn starch or arrowroot starch as a thickener. Disperse 2 teaspoons of starch in 30 ml cold water and add this mixture to the soy milk just before boiling.
If you are using store bought soy milk, you should buy one with absolutely no sugar or flavourings added. Many soy milks add vanilla flavouring, which will spoil the taste of the yoghurt.
For the starter- You could also buy jamaa (a starter) online, or soak whole moong beans overnight and use the water as a starter. Alternatively, 10-12 chilli crowns may be used as a starter.
Try making a small amount first, since yoghurt can be a bit unpredictable the first few times. With the chilli tops, you may need to reserve some of the batch and use again with a fresh batch and more chilli tops, until you get a firm set yoghurt, which can be used as a starter for further batches. A starter portion of yoghurt or a starter culture normally gives reliable results.