All you need to make homemade yogurt is yogurt starter, milk, and a way to heat the milk and keep it warm. I use a yogurt nest made from items I already had. Read below for how to create your own yogurt-making environment, then see the Cook for Good yogurt recipe, which includes a video of making the yogurt and tucking it into the yogurt nest.
Yogurt starter is just fresh yogurt in which the yogurt culture is still alive. Most yogurt sold in stores contains live yogurt – those that do should say so on the container. Look for a statement like this: “Contains active yogurt cultures including L. acidophilus.”
If you can find it, buy plain, unflavored yogurt. If you can’t, look for “fruit on the bottom” or unmixed flavored yogurt. You are after the yogurt culture, not the jam. I usually use Dannon’s All Natural plain yogurt.
When you buy a container of yogurt to start your own batch, freeze any you don’t need immediately in a clean ice-cube tray. The next day, pop the yogurt cubes into a freezer bag or container and keep it in the freezer. The culture will stay alive for months. Just take out a yogurt cube when you are ready to make a fresh batch of yogurt.
If you make yogurt every day or two, you can just use a spoon full of yogurt from one batch to start another. That’s how people in Turkey and India have done it for centuries. But if you make it just once a week or so, bad cultures will start to take over the good cultures. Most people start each batch with commercial yogurt. But you can save money by freezing cube or two of a batch you've just made just after it’s cooled. That will at least delay the takeover by the sour cultures so you don’t have to buy yogurt to refresh your culture more than a few times a year.
Making a yogurt nest
A yogurt nest will keep the milk and yogurt starter warm and cozy enough to make good yogurt. Yogurt culture grows best between 86 and 113 degrees. Using lower heat takes longer but produces silkier yogurt. Yogurt made at higher temperatures also releases more of its whey, making it more watery. Bumping, stirring, or moving the yogurt can disrupt the formation of the protein network that makes yogurt yogurt.
I use a box or a cake carrier, a heating pad, and an old bath towel to make a yogurt nest. Put one end of the towel on your counter. Put the heating pad on the towel and your yogurt container on the pad. Cover them all with the box and then flip the towel up over the box to trap the heat. I use the SoftHeat dry heating pad set on low.
Before you make your first batch of yogurt, test the nest by filling your containers with warm water (about 110 degrees). After an hour, check the temperature of the water. Adjust the temperature on the heating pad until you find one that will keep the water inside the safe range between 90 and 110 degrees. Make a note for yourself of which setting works best.