This is the second in a series of posts about making yogurt at home. The first post ended with a very brief description of the yogurt-making process. Milk is scalded to denature its proteins; then it’s allowed to cool to a safe temperature before adding a starter culture. At this point, the yogurt must be held at a temperature of about 110 degrees for a period of 8–12 hours. That temperature allows the bacterial culture to multiply, turning your milk into yogurt.
A stand-alone yogurt maker, or the yogurt function on an electric multi-cooker like an Instant Pot, is designed to hold that 110-degree temperature.
I first made yogurt using a stand-alone yogurt maker. Later, when I bought my first Instant Pot, I gave my yogurt-maker away, thinking I no longer needed it. There are some benefits to making yogurt in the Instant Pot, but for other reasons I eventually decided I liked a stand-alone yogurt maker, and I recently bought a new one and went back to that method.
Stand-alone yogurt makers are very inexpensive, even when purchased new. You can also find them at yard sales or thrift stores; a yogurt-maker is exactly the type of thing that might be received as a gift and left more or less unused.
There are two types of stand-alone yogurt makers. One kind incubates yogurt in individual, single-serving jars. The other type incubates yogurt in bulk (typically, a quart at a time). Which type you use is up to you — but if you plan to strain your yogurt, converting it into Greek yogurt, you’ll probably have to do that in a big batch anyway, so you might as well make the yogurt in bulk and then parcel it into individual servings later, after it’s been strained. Both of my yogurt-makers have been bulk machines.
One advantage of the individual-jar machines is that people who like to flavor their yogurt at the beginning of the process — before incubating it — can flavor individual jars separately. I always flavor my yogurt after the fact, so this isn’t an issue for me. If you do individually-flavored jars, you should leave one jar plain so that you can get your starter culture (for the next batch) out of that jar, or in case you need plain yogurt for a recipe. You can always flavor that last jar right before eating it.
There’s another type of yogurt-maker you can buy which is not an appliance and which does not require electricity. The YogoTherm and other such devices are actually sort of glorified thermoses. They are designed to keep yogurt warm by insulating it. I’d like to try one of these, but I haven’t yet. The online information seems to indicate that they’re good for incubation times of 8 hours, which for me would be on the short side, but would certainly be sufficient to produce a good product. And there are benefits to not having to plug in an appliance. You could set the insulated container somewhere out of the way — and if it’s a warm place, like the top of the fridge, that would be a little insurance.
But there are also methods of incubating yogurt that involve things you already have around the house. I have not tried any of these myself, and I’m going to recommend that if you want to try one, you do a test run before wasting any milk. Even though these recipes have been used successfully, they depend on the capabilities of your particular appliance, which may be different from the appliances of the person who developed the recipe. Here’s how I would check: fill the vessel with water (115 or 120 degrees) and follow the recommended method. Then, after four or five hours, check the temperature of the water using an accurate, easy-to-read thermometer. It should be in the neighborhood of 110 degrees. If it’s not, you may have to make adjustments or find a different method.
Method #1: The electric blanket. This is the method which Alton Brown used on an episode of “Good Eats.” Alton famously despises single-use gadgets like yogurt makers, which he calls “unitaskers.” Scalded, cooled and cultured milk is placed into a glass jar with a lid, and then the jar is placed in a wine bucket which has been lined with an electric blanket or heating pad. Alton suggests setting the pad on medium, but your test run — remember, I’m recommending a test run — will determine if that’s the right setting for your blanket. Also, make sure your blanket doesn’t have an automatic shut-off timer; some do.
Method #2: The oven. If you have a gas oven, the pilot light may generate enough heat to hold the interior of the oven at about the right temperature — provided you leave the oven CLOSED and do not open it at all during incubation. If you have an electric oven, the interior light bulb, when turned on, may do the same, again, if you leave the oven CLOSED the entire time. (Have oven-makers switched to using LED bulbs? They don’t put out as much heat, and so they would probably not work for this.) Put your scalded, cultured milk into a glass jar with a lid, and place the jar inside the oven.
Method #3: The slow cooker. This one comes from several sources, but I’ll link to it from the Crock Pot brand website. The slow cooker is used to scald the milk. Then, you turn off the slow cooker, leave the milk in the crock and allow it to cool before adding the culture. (It will take longer to cool using this method, and you must not add the starter culture until the milk is 115 degrees or lower, because the scalding temperature of 180 degrees will kill the bacteria.) The slow cooker is then wrapped in a towel to insulate it and left undisturbed in a warm place.
Method #4: The chest cooler. I almost didn’t include this one, because it seems the most suspect to me. I am recommending a test run with any of these jury-rigged methods, and that goes double with this one. In this method, the cultured milk is placed into glass jars, which are placed in a big rectangular chest cooler. Two big gallon milk jugs are filled with very hot water and are placed into the cooler along with the milk. In some versions, hot water is poured directly into the cooler. As with the oven method, you must leave the cooler closed and undisturbed once it has been loaded. If you’re using the milk jugs, you can swap them out for fresh hot water halfway through if necessary.
That gives you a number of methods to choose from. As I said, I like having an inexpensive yogurt maker. But if you don’t have one or want to get one, that shouldn’t be a barrier to at least trying a batch of yogurt.