In India, they heat milk and then add the juice of 1 lemon and let the milk sit out overnight to culture yogurt. Aajonus Vonderplanitz (big raw foodie) makes it by just letting raw milk sit out for about 3-4 days in a mason jar until it cultures. I do this often & don't even add extra starter culture & find it highly digestible...I recommend Claravale raw milk if you live in CA. I work for a naturopath & he has issues w/people fermenting live cultures w/electrical products because it can mutate the bacteria. I say go back to nature & do it the way of the ancients! Obviously, the choice is yours...there is always more than 1 way to do anything. You can also check Sally Fallon's book Nourishing Traditions to read more about making your own cultured dairy. Enjoy!