I know, I know, it’s not normal for most of us in this day and age to leave dairy products sitting out at room temperature. Most of our kitchen devices are designed to prevent spoilage, which — let’s face it — is pretty much what fermentation is. It’s therefore not surprising that so many of you would have written me asking, in essence, are you really sure this won’t kill me?
The reality is that lactic acid bacteria are all around us. They’re present on surfaces, in the air, but more importantly in the bodies of ruminants like cows, which is where the bacteria that we use to make yogurt ultimately come from. Indeed even the milk we buy in stores, though it’s been pasteurized, is rife with them. Innoculate that milk with a yogurt starter, buttermilk or sour cream and you set off a bacterial feeding frenzy that produces acid on a scale that either kills off or neutralizes most of the microbes that can do you any real harm.
I’m not going to say it’s impossible that something unpleasant and/or harmful could move in despite the hostile environment, just very unlikely. This is what I mean about fermentation being miraculous. The fact that lactic acid bacteria behave this way naturally, in a way that’s beneficial to humans, is amazing.
Travel back in time 100 years or so in North America and you’d find something called a “clabber jar” in every rural kitchen. The clabber jar was a vessel into which farm wives would pour fresh (usually leftover) milk, buttermilk or cream, then let it sit at room temperature until it soured. The “clabbered” milk would be eaten as-is or used as a leavening agent in cakes or biscuits, mixed with baking soda. The sour buttermilk would be iced and consumed by farm hands like a soft drink. As for the sour cream, well, that’s where it came from before there were dairy cases.
Did people ever get sick eating/drinking out of the clabber jar? On occasion, but most of the time because their cow was sick, not because some random bad guy microbe moved in out of thin air. Thus my advice, while I know home fermentation is a little intimidating to most of us, is to clabber away. But need I say that should you, at the end of the day, culture something that looks, smells or tastes “off” in any way, do not hesitate to throw it out.