Makes: Approximately 1 quart
- 1 quart of skim or low fat milk
- 1/2 cup of non-fat powdered milk
- 4 oz plain yogurt with live cultures
- Honey or Sugar to taste
- Combine milk and powdered milk in sauce pan.
- Heat sauce pan on medium heat to 200 degrees Fahrenheit stirring occasionally to dissolve the powdered milk. Do not allow the milk to boil!
- For a sweeter yogurt, completely dissolve sugar or honey in the hot milk. Be careful not to scald the sugar or honey.
- Remove sauce pan from heat and cool to 110 degrees Fahrenheit.
- In a heat resistant bowl or measuring cup, add the plain yogurt and slowly temper a small amount of the cooled milk into the yogurt.
- When the temperature of the yogurt has reached the same temperature as the milk, add it to the milk stirring gently.
- Place the entire mixture into one or more containers and hold the temperature of the containers at 110 degrees Fahrenheit for 2-3 hours.
- Refrigerate the containers of yogurt.
- Retain a small amount of homemade yogurt to inoculate your next batch.
Yogurt can be stored in the refrigerator for 1-2 weeks without spoiling.
To hold the yogurt at 110 degrees Fahrenheit, you need to use an incubator of some sort. Commercial yogurt makers are simply an incubator which consists of a container, a heating element and a thermostat. If you are making individual cups of yogurt, use your oven as an incubator by placing a casserole dish filled with a hot water bath inside. The containers can then be placed in the hot water bath and the temperature can be monitored with a meat thermometer. If you are making yogurt in one or more quart size containers of yogurt, an insulated cooler and a heat pad with an adjustable thermostat work well. Again use the meat thermometer to monitor the temperature in the cooler. While 110 degrees is the optimal temperature for the bacteria, a slightly lower temperature will only slow down the fermentation process and thus requires more time. Be careful if using a higher temperature, the process may be slightly faster, but you risk killing the bacteria in the yogurt. The end result will be sour milk.
Yogurt is essentially a type of cheese. Instead of using rennet to cause the proteins in the milk to entangle and form a solid, live bacteria are added which cause fermentation to occur. While bread, ale and lager yeasts excrete CO_2 and alcohol as they consume sugar, the bacteria in yogurt excrete an acid that causes the proteins in the scalded milk to coagulate. The sugar that yogurt bacteria consume is lactose which means that it is possible that yogurt will not cause upset stomach in people that are lactose intolerant. This is important because yogurt is a good low-fat source of protein and calcium.