½ gallon of Whole Milk
½ cup of Powdered Milk
1 container of Commercial Yogurt (yogurt from market that contains active cultures.)
- Heat Milk: Heat ½ gallon of milk to 185 degrees F. Any type of milk will work, e.g. fat free, 2% or whole. This should take about 25 minutes in a 500 watt microwave. The temperature can be measured with a candy thermometer. Don't boil the milk.
- Add Powdered Milk: Stir in ½ cup of powdered milk. The additional milk solids make the yogurt thicker.
- Cool Milk: Let the milk cool to 115 degrees F or less. The yogurt does not seem as sour if you cool to 105 degrees. Once again, you can measure the temperature with a candy thermometer. This should take about an hour and a half at room temperature.
- Add Culture: Add one container of commercial yogurt with active cultures. Vanilla or plain works bests. Other flavors will add color and flavor, though they will work too. We've been using the Safeway store brand, low fat and calorie vanilla.
- Strain Mixture: Strain mixture with tea strainer to remove excess dry milk. Otherwise the excess dry milk will leave grit at the bottom of the bowl.
- Incubate Culture: Cover with plastic wrap, and let sit at 105 to 115 degrees for 8 hours. If you turn your oven light on and set the bowl in the oven all night, this should work. Wrapping the bowl in a bath towel with a heating pad turned on low will also work. Don't let the temperature go over 115 degrees or the culture may be killed.
- Cool: Place bowl in refrigerator. After a few hours the yogurt should be cool and ready to eat.