It's even simpler than the crock pot method, if you can believe it! Y'all, seriously, if you or your kids go through carton after carton of pricey store-bought yogurt, you need to take this method for a spin. Sorry, no pictures this time; this was a spur-of-the-moment creation motivated by my need to get a half-gallon of milk out of my fridge.
A note on incubation: there are several ways you can keep the inside of your cooler warm for incubation. I put about two inches of hot tap water (around 140 Fahrenheit; if yours isn't this hot, put a little boiling water in as well) in the bottom of the cooler, and filled three quart jars with hot water to set around the jar the yogurt was in. Then I covered the yogurt jar with foil and placed a big towel down over the tops of all the jars and zipped the cooler shut.
- large glass bowl
- small glass bowl or measuring cup
- stainless steel (or other non-reactive) spoon
- mesh strainer or cheesecloth or tea towel
- thermometer that goes up to 190 (I used my cheapo meat thermometer; you can use a candy thermometer or I'll tell you how to gauge the temperature without one)
- large glass jar or several smaller glass jars (you can use any clean, empty food jar)
- incubation jars (see note above)
- medium-sized cooler
- half-gallon of milk*
- 1 cup nonfat powdered milk
- 6-8 oz cup of plain, unflavored yogurt with active cultures
- 2 T. sugar (optional; the addition of sugar makes the end product MUCH less tangy, so if you prefer a tangier yogurt, just omit this)
1. Pour milk into glass bowl and place in the microwave. Microwave on high for 2 minutes. Stir, and microwave for another 2 minutes. If you have a thermometer, begin checking the temperature now -- you're aiming for 180-190 degrees Fahrenheit. If not, keep an eye on the milk and continue microwaving in 1-minute intervals until milk bubbles around the edges and steams vigorously. 190 is just shy of boiling. Don't let it boil.
2. Remove bowl from microwave and stir the milk gently for about a minute. Stir in the powdered milk. Allow the milk to sit at room temperature for 30-60 minutes, or until it is between 110 and 120 Fahrenheit. You can test the temperature against your wrist if you don't have a thermometer; it should feel quite warm but not make you say, "Ouch!"
3. Take out about a cup of the warm milk and put it in the small bowl or measuring cup. Stir in the small container of yogurt. Add this mixture back to the large bowl of milk. Add the sugar, if you're using it.
4. Strain the mixture into jar or jars. This step isn't totally necessary, but I found that it strained out the bits of powdered milk that hadn't dissolved completely. Cover jar(s) with foil.
5. Place the yogurt jar(s) into the cooler along with the jars of hot water. Cover with a towel and incubate for 8-14 hours. Overnight is perfect for this! If your kitchen runs cool or when you're making this in the winter, give it a little boost of hot water an hour or two before you're going to take it out. A longer incubation tends to make thicker yogurt, but I only did about 8.5 hours and still ended up with yogurt that's plenty thick -- thick enough to stand up on a spoon! :)
6. Remove the yogurt jar(s) from cooler and refrigerate until cold. Keeps for two weeks. To flavor, stir in jam or preserves, honey, fresh or frozen fruit, granola, or any combination of the above.
*Re: milk. I've found that full-fat milk works best for thick, creamy yogurt and that the lower-fat your milk is, the runnier the set tends to be. I also used non-homogenized milk, so I ended up with cream-top yogurt! Yum!
If you have ANY questions or if something in my instructions isn't clear, please let me know in the comments section and I'll do my best to clarify or adjust!