Yes, I'm afraid other things decomposed by the bacteria that turn sour in milk are toxic. . . .

It is best to use the specified flora (powder).

Sure, just use the pure yogurt (original) thick one sold outside.

Just put it in the milk, just like the mushroom powder.

Yogurt is the reproduction of lactic acid bacteria. Yogurt is the flora that thrives in milk. Of course, it can.