Yogurt is a traditional method of preserving milk that adds beneficial bacteria to the milk product. The process is fairly simple: heat the milk to scalding to kill competing bacteria, cool the milk to about 110° Fahrenheit, add a bacteria starter, and keep the milk at 110° Fahrenheit for twenty-four hours.
1) Starter. Use about a one-quarter-cup portion of a live culture yogurt for every quart of milk. Warm to body temperature, or about 100° Fahrenheit. Alternatively, buy a yogurt starter, a more foolproof method.
2) Stainless steel bowl or pot to heat milk. (See double-boiler method below.)
3) Container to culture yogurt. This can be a glass mason jar or the container that comes with a yogurt maker.
4) Optional: digital thermometer with alarm. (Alarm sounds when the heating milk reaches the desired temperature.)
Heating milk, adding starter:
1) Use a double-boiler method to scald milk. I put the milk in a large stainless steel bowl and set the bowl in a sauté pan filled with water.
2) Set a timer so that you remember to check the milk as it cooks on the stove. Alternatively, use a digital thermometer with an alarm set at 180° Fahrenheit.
3) Pull the milk off the heat just before it boils.
4) Set the milk on the counter in an out-of-the-way place and set your digital thermometer 110° Fahrenheit. Without a digital thermometer, check the milk every twenty minutes (set a kitchen timer to remind you). It is ready when it is just above body temperature. Do not stick your finger in to check the temperature. Take a small amount out with a spoon and drip it onto the back of your hand. When it is no longer hot to the touch, it is ready for starter.
5) Have all your containers ready so that when your milk is ready for the starter, you do not have to go into a frenzy.
6) When the milk cools, add some to a smaller bowl or cup. Add the starter to this smaller container. Mix it in well. Add the mixture to the main bowl. Mix well.
7) Pour the milk with the starter mixture into the yogurt containers. Set in a warm location for twenty-four hours. See “keep warm” next.
Keep it warm:
This is the step where people find a yogurt maker to be handy. Yogurt makers will maintain a temperature of 110° Fahrenheit. I used the Yogourmet yogurt maker because I could make a half gallon at a time and it would hold its heat for as long as I wanted to culture the milk. I have given the yogurt maker away, however, because I make one gallon at a time now. A yogurt maker is convenient for smaller quantities, but it is not necessary.
The key is to keep your milk at about 110° Fahrenheit. The yogurt will be forgiving, however. Some of the more common methods include the following:
1) Cooler. Put your jars of milk in a cooler, in a few inches of warm water. The water helps maintain a warm environment in the cooler for the twenty-four hours. In the summer I put the cooler in a sunny part of the house with a blanket over it to regulate the temperature over the whole cooler. In the winter I put the cooler near a woodstove with a blanket over it. In the winter I also change the water at least once in the twenty-four hours to keep the warm environment in the cooler. A cooler too close to the woodstove is a bad idea. This is where trial and error will help find the right spot.
2) Oven. If you have an oven with a pilot or an oven light that maintains a warm environment, this might be a good location for your jars. A warming drawer could also work.
3) Heating pad. Experiment by keeping your yogurt warm on a heating pad.
Raw milk yogurt
Follow the recipe above, but heat the milk to 110° Fahrenheit. Once milk hits 110°, add starter and keep warm per the instructions above.
Note that raw milk yogurt does not tend to congeal as well as pasteurized yogurt. Expect something more like a yogurt drink.