Since yogurt is almost all milk, this step matters, as it will have big impact on your yogurt’s consistency and flavor. Contrary to what you might think, whole milk, while it does deliver more fat, doesn’t make home-made yogurt thicker. In fact it makes it thinner, or perhaps I should say “soupier”. For reasons I’ll discuss in detail later, it’s protein that makes yogurt thick, not fat. The more protein you have, the better the gel you get. Since most American dairies supplement their skim and low-fat milks with extra protein to improve “mouthfeel”, lower fat milks are preferred.
This is not to say that soupy yogurts are a bad thing. I quite like a good whole milk yogurt even though it wants to run off the spoon instead of stand upright on it in a quivering slice. It’s luxurious, like cream, though with much less fat. So it’s really all up to you. As you’ll see as I march through the process, the recipe below is just a guide.
I also want to mention that when it comes to your milk, you need not feel limited to what you find in the market dairy case. For that matter, you need not feel limited to cows. Depending on where you live, you might be able to procure something a bit more exotic. Most health food stores carry goat’s milk these days, and if you’re really enterprising and live in a rural area, you can sometimes find it fresh. The same goes for cow’s milk. Laws concerning the sale of raw milk vary from state to state in America. Here in Kentucky it’s not legal to sell “raw” milk even in a health food store, though it’s not illegal for health food store owners to connect you with a farmer who’ll sell you a “share” in a cow for the price of a gallon of its milk (the legal loophole being that it’s not milk that ‘s actually being sold, but rather livestock, the milk from which an owner is free to drink if he or she pleases).
So look around. You might be surprised at the milk products you might find. For those of you in the US a partial list of raw milk sellers can be found here. Those not living in the US can try their luck here.