But wait, if I use yogurt as a sour cream starter culture…

…won’t I just make more yogurt? That question from a few folks overnight. The answer is no. But why? Because yogurt cultures, like all fermenting cultures, are composed of scores of different types of microbes. Some grow better than others depending on things like temperature and humidity. The bacteria that create the stiff gels we associate with yogurt don’t grow well at low temperatures (which is to say, under about 110 degrees). The more conventional lactic acid bacteria that are adapted to local conditions will therefore prevail. Your cream will end up looking and tasting like regular ol’ sour cream.