When I make yoghurt at home the result is different every time even though I follow exactly the same procedure:
- Bring a gallon of milk to 85°C
- Cool to 43°C
- Add yoghurt culture from the previous time
- Keep it at 43°C for 2-3 hours or until ready
- Cool it to refrigerator temperature
Milk is always of the same kind from the same store (Costco). I use thermometer and keep the temperature with 1°C precision.
Sometimes it is extremely creamy, soft, homogeneous, and almost sweet, and sometimes a lot of whey forms on top and it becomes very sour.
Obviously I like the the former outcome rather than latter one.
I can't figure out what is wrong, why it is different every time?
I also noticed that when I start with the store-purchased culture the first batch is likely good (creamy).