You can obtain it from raw organic milk, free - range animal foods and eggs. (huffingtonpost.com)
FYI I am using raw organic milk from a Jersey and organic apple cider vinegar. (amazinggrazefarm.com)
I have always made this from raw organic milk soured 1 to 2 days, using the buttermilk from the separated cream as starter culture.250 mls to 5 litres skimmed milk. (peanutbutterboy.com)