Yogurt

I've been making my own yogurt lately. Thanks to this Jane Galt post, I got this yogurt maker from Amazon. It's unbelievably simple: You heat a quart of milk, not to a boil, but slightly short of that, to a point where a little steam is rising from the milk. This is to make sure that any bad bacteria are dead. Then you let the milk cool to around 100-110 degrees (the yogurt maker comes with a thermometer for this purpose). Then you mix in a few tablespoons of existing yogurt (the source of good yogurt bacteria). They say you should use plain yogurt here, not flavored; I think this is because of the risk that fruit-flavored yogurts might have extraneous bacteria in the fruit.

Now that it's all mixed up, you pour into the little cups that fit inside the yogurt maker, which simply keeps them at a constant warm temperature. That's it. Several hours later, it has fermented into yogurt.

Total prep time: About 5 minutes of actual work.

One thing I notice is that it is runnier than store-bought yogurt, which is usually thickened with corn starch.

As for the starter, I like to use Stonyfield yogurt, because it is made with L. Reuteri, a bacteria that seems to have several health benefits. See here and here.

One thing that occurs to me, though, is this: How did humans ever figure out how to use only good bacteria in making fermented milk products (yogurt, cheese, etc.)? Yogurt was invented so long ago that no one seems to know. But think about it: A thousand or more years ago, how did people tell yogurt apart from spoiled milk? Ugh.