So how do you make such a masterpiece?
The first step to find a good quality culture - I used to use just plain yogurt from the grocery (be sure it says "active cultures") and preferred Dannon brand. You can also get starters from Cultures for Health. They have both heirloom starters and one-time-use starters. Right now I'm using Custom Probiotics Yogurt Starter #1 (they have two different ones.) There are lots of options out there and it's worth trying a few and finding your favorite. You can save some yogurt from a previous batch of your own to use within a couple weeks, but just be aware that it must be "pure" (not raw milk yogurt) and overtime the strength of the culture may fade. I could go about 2 batches past the store starter. Freezing starter only seems to extend the life of the cultures a week or two.
The next step is to heat (or not heat) to prepare the milk for culturing. Milk heated to 180º F will be thicker in the final product, milk kept closer to raw (so only heated to 105º F or so) will have more complex probiotics and the benefits of being raw. This type of heating is *not* the same as pasteurizing, which is an intense method and quite destructive of the milk. If your milk comes to you pasteurized though, do heat to 180º before making into yogurt, as you are more likely to have undesirable cultures in the milk, and you don't want to promote those! I hate heating milk, but I think breaking down the proteins somewhat, especially in such a gentle way, helps make it more digestible too. My dear husband likes the flavor and thickness that way as well.
Before heating, make sure your tools are perfectly clean, sterile is ideal, but I don't stress it personally. I just pour my milk into a pot and use a thermometer to check. Once it hits 180º F, I turn the heat off and stir throughout the heating and cooling time. For a crockpot method, heat on low for about 2 hours.
After heating, cool to about 110º F before adding your cultures. Adding them when it is too hot will kill them. Yogurt cultures are finicky about temps. For store yogurt, add about 2 heaping Tbsps culture per half gallon of milk. For other starters, follow the included instructions. Mix very thoroughly. Avoid stirring with plastic, as plastic never truly comes clean and tends to harbor other bacteria.
Now here is the tricky part... how to keep it nice and cozy warm (and undisturbed!) for 24 hours. If you only want standard yogurt, 8 hours is fine, but for GAPS yogurt, it needs to go the full 24. This helps eliminate all of the lactose. Some yogurt makers have a lot of trouble staying warm long enough, though if you have one it is worth a try. Some people like the cooler method, or going in the crockpot, or a warm oven, but I have a dehydrator now and love it's consistent temp control! However you decide to tackle this, the temp needs to be about 95-110º F consistently for the whole duration, and sit in a spot where it won't be bumped or jostled during culturing.
For the crockpot - at least in summer - heating the milk for 2 hours on low, then turning off and adding cultures 2 hours later, and then sitting with lid on for the next day can work well... If you can find a warm spot in the house, put a towel over it (cultures don't like light) or a empty microwave that will keep the light on with the door cracked... use a spot like that. Check and see if it keeps the temp you need.
A heating pad inside an oven is another effective method, just check that your heating pad doesn't have an auto-matic shut off! The oven insulates, so when I did this I just had the yogurt on one rack and the heating pad on another.
For the cooler -hot water method, check out this link.
In the dehydrator, just put it in, and turn it on. It must be a dehydrator with temp control, such as an Excalibur. I got one for cheap on Ebay and love it.
Once it is finished culturing, stick it in the fridge. I find it does better if I don't stir until it has cooled. It has a smoother consistency. Some fancier-bloggers out there have experimented with adding gelatin or sweetening or other fun stuff, but I like to keep it simple.
Finally - just a quick note on containers. When I started, I was so super fancy, I just used a big ol' pyrex bowl. It was what I had and it worked. Later on I switched to Mason jars, and now I use Fidos. A sealed jar helps prevent other cultures that live in your house from entering in and taking over. Yogurt cultures are weaklings, I'm sorry to say. You have all kinds of yeast and other microbes hanging out in your house all the time, even if you don't have kombucha, kraut, carrot pickles, and a hundred other ferments bubbling away nearby, and if any of them pop in and start chewing on the milk sugars before the yogurt guys do, then all of a sudden you'll have yeasty milk instead of yogurt. Kefir is a much more robust culture (it is far far more complex) and is a lot less picky. So by fermenting in sealed jars (and burping them before going in the fridge) I can avoid yeast-yogurt that is only good for breadbaking. And it tastes better too! If you have an air-lock on your fancy jar and it fits in your fermenting hot spot, even better.
So there you are. You have conquered the mystery of yogurt making, and you can culture the world! Or at least your stomach.
Sweeten to taste if desired, strain for cream cheese, use to thicken sauces, as a base for smoothies, ranch dressing, or soak your skin in it. Yogurt is wonderfully useful.
Curious about other ways to make yogurt? Here are some other methods and tips:
Raw Yogurt - cooler method
Incubator method and oven & heating pad method
Another heating pad method for smaller batches
Coconut milk yogurt (I would recommend sweetening with honey, not agave though.)
Getting Whey & Cream Cheese - Video
Another cream cheese method from buttermilk
How do you like your yogurt?
