Did you know you can make yogurt at home? And that it's really easy? You basically need a pot and milk and you're set. I started making my own yogurt when we were on a very tight grocery budget - when, yes, the $2 per week that it saved was significant. And even though we're not strapped for those few bucks anymore, I've kept it up. OK, to be completely honest, I still try to save here and there if I can - it adds up, after all! But really, I just find it satisfying to produce some of the things I enjoy in my daily life. I remember the first couple of times I made it, it was almost like magic. I still find it kind of marvelous, kind of like every time I take a loaf of bread out of the oven I'm amazed all over at the process.
You do need a little bit of yogurt with live active cultures to start. (Most yogurts have live cultures, but just check on the container, it will say.) You only need 1/4 cup to produce a whole batch of yogurt and then you can perpetuate that for quite a while. I'll go through the process and then include a list of notes and tips I've gathered along the way.
what you'll need:
half a gallon of milk (I always use whole milk)
1/4 cup yogurt with live active cultures
plain white paper towels or cheesecloth
what to do:
Heat the milk over medium high heat, stirring occasionally, until thermometer registers 175 - 180. Remove from heat and let cool. If a skin forms on the surface, simple remove and discard
When the milk is around 110 - 115 (any warmer and it will kill the active cultures; any cooler and it won't be warm enough to support the active cultures sufficiently), stir in the 1/4 cup yogurt. Cover with lid or plastic wrap.
Now for the incubation period. Your goal here is to keep the milk warm enough for an incubation period of anywhere between 8 - 12 hours while the cultures do their work. The way I do this is to preheat my oven to its lowest setting for a few minutes, wrap the pot of milk in a big towel, turn off the oven, stick the wrapped up pot in there, turn on the pilot light, and leave it.
After 12 hours, remove the pot and - voila!- it's yogurt. Stick the pot into the fridge to let it cool and thicken. There is no definite time frame on this. Move onto the next step when you get around to it.
When cool, you can thicken your yogurt by straining out some whey. Line a colander with plain white paper towels or a cheesecloth. Pour the yogurt in and let strain until desired thickness. The whey will collect pretty quickly as the yogurt settles. This has no definite time frame either, but the longer you leave it to strain, the thicker it will get.
After straining, dump out of the colander into a bowl and whisk until smooth. Store in a container and enjoy! Don't forget to reserve 1/4 cup of the yogurt for your next batch!
You can perpetuate the same strain of yogurt maybe 4 times over but then it starts to get weaker.
...in which case, when I first get started, I buy a carton of plain yogurt and freeze 1/4 cup portions in a cupcake tin, then store in a ziplock bag in the freezer. If I've forgotten to set aside the last 1/4 cup of my batch, or it's starting to get weaker, I simply take one of these yogurt "pucks" out of the freezer and allow to thaw and use that as my culture. When I'm getting low on my freezer supply, I freeze a whole bunch more of 1/4 cup portions from the next fresh batch I make.
Generally speaking, the warmer the incubation, the more tart the yogurt. It will still turn into yogurt but it won't be as sour. My summer batches are usually more tart.
As far as timing goes, I have found it works well for me to start heating my milk after dinner, letting it cool as we get kids to bed, tidy up, watch a show, etc, and letting it incubate in the oven over night.
Whey is supposed to be pretty nutritious. I have used it in soups, smoothies, and as the bread for my liquid. It is not buttermilk and cannot be used as buttermilk, but it does have a similarly tart flavor. Go ahead and experiment with it or just discard it.
As far as sterilization/contamination concerns go: I do not boil or sanitize all my equipment. I make sure they are all clean and I am reasonably careful not to let any foreign matter get into the milk during the process. In the 8 years that I have been making yogurt - so something like 150 batches of yogurt, I have only ever had one batch that I thought tasted off and threw away just to be safe.
Do not agitate the yogurt during incubation! Give it at least 8 hours before moving around. Otherwise, in my experience, you end up with a more curdled texture.