The process for making yogurt at home is quite straightforward. That's not to say there's no effort required. Mainly, you have to keep a rather careful eye on temperatures, but aside from that it can be a fairly simple operation.
Just what are the reasons for making yogurt in your own kitchen? For one thing, you'll likely find it less expensive, maybe quite a bit less expensive, than buying it at the store. Admittedly, if you only have a cup of yogurt once a month or so, making it at home is probably not going to be worth the time and effort, but if you eat yogurt often, or use it with other foods, you may find making your own to work to your advantage.
We tend to get used to the taste of a particular brand, and fear that by making yogurt on our own, somehow the taste won't be nearly as good as we've become accustomed to. The taste no doubt will be a little different, but it can just as easily be better, as it can be worse. Plus, you have the opportunity to try a number of different flavors, or work with a number of different recipes, and eventually end up with yogurt that is very good indeed. Also, you don't need special equipment for making yogurt.
The Equipment You'll Need - A candy thermometer is probably the only item you will need that you may not have in your kitchen. If you do have a candy thermometer, you have the most important item already. There are yogurt machines on the market, and if you plan on making lots of yogurt, a machine may be worthwhile looking into. But we'll touch on that a bit later.
Here's The Process - If it sounds too simple, bear in mind that there are some things you have to watch for along the way. We'll be discussing each of the following steps in more detail of course. There are five steps: (1) Put milk in a pan and heat it to near boiling. (2) Let it cool down, but not to room temperature. (3) Add some yogurt starter. (4) Incubate the mixture at a warm temperature for several hours. (5) Chill in the refrigerator. And that's basically what there is to it. The optional 6th step, which you'll probably want to do, is add some flavoring, like crushed fruit, or whatever strikes your fancy. You do this at the end, usually just before eating it.
One important step in making yogurt that wasn't mentioned above, but probably should have been, is preparation. Before you get started, every thing must be clean. That means cleaning your pots, pans, and utensils, the containers you plan to put the yogurt in, and even the thermometer. Wash in hot water with soap or detergent, and then rinse well so that no soap scum or detergent remains. Yogurt is largely fermented milk, and you don't want detergent or stray bacteria messing up the fermentation process.
Step 1 - Put Milk In Pan and Heat - What kind of milk is best for making yogurt? Just about any kind will do. Milk with a higher fat content will give you a thicker yogurt. But skim milk will work fine. Just make certain it is pasteurized milk. We usually use cow's milk here, but in many countries goat's milk is the one of choice. It you own a yak, that will do fine as well. You can even use soy milk, though not soy milk powder. If you use soy milk you have to add fructose or honey to initiate with the fermentation process. As far as heating the milk, a double boiler is best, if only because it will keep the milk at a steady, controllable temperature. One quart of milk will do for a beginning, and to that you'll need to add milk powder, 1/3 of a cup for whole milk, and double that if you're using skim milk. Mix the powder with the milk and you're ready to heat it up.
Why are we heating the milk? To kill off any bacteria that may interfere with the fermentation process. We'll be using warm milk in any event, but first you want to heat the milk and milk powder mixture to 200 degrees F for 10 minutes. You don't want to boil the milk; the thermometer comes in handy here. If you want your yogurt to not be quite as tart, you can add some honey, or another sweetener before bringing the milk to a boil. You might need to do a little experimenting to see how much sweetener you need, if any. Or you can just wait until it's ready to eat and add sweetening and flavoring at that time.
Step 2 - Let The Milk Cool - After heating the milk for 10 minutes, let it cool down. In making yogurt this is where the thermometer is really put to good use. You don't want the milk to cool all the way down to room temperature, but rather cool it down to 115 degrees F. You can allow the milk to cool down a few degrees more, but don't let it get below 100 degrees, and anything in the range from 112 to 115 degrees is best. (continued...)