We don't usually associate cooking with chemistry but cooking really is a chemical process. Instead of a recipe it is a formula. When we subject food to heat, there are several changes in both physical and chemical composition. In the manufacture of yogurt we see a special kind of change due to fermentation. Better known for making alcohol, fermentation has some very interesting properties. We will be breaking down the protein in milk to make a tangy, and probiotic rich food. Any kind of milk can be used, but regular milk from cows will be used here. It can be whole, 2%, or skim milk. The fat content will remain the same as what we start with. We will be making a small batch size to illustrate the easy, and fun way to make yogurt at home. Scaling up is easy as well, and the process is exactly the same.
Parts and pieces...
- 1 Cup milk, whole, 2%, or skim
- 1/2 Tablespoon plain starter yogurt. Any commercial kind with active cultures
- 1/8 Teaspoon sugar
- Glass container, microwave safe if using microwave oven
- Fahrenheit or Celsius thermometer-Helpful but not absolutely necessary
I am showing how to make yogurt on the stove top but the microwave works as well. Just use a microwave safe container. The first step is to scald the milk. A temperature of 180 F ( 80 C) will be fine. We don't want to boil the milk, just scald until a skin forms on top. This will kill any bad or competing bacteria. Let the milk cool to about 110 F (43 C). If you can put your finger in the milk for a few seconds without being too hot it is close enough. Add the starter yogurt and the sugar and stir well. Bacteria thrives on sugar and it really promotes good conversion. Now, set aside for 4 to 7 hours. It is important to keep the container warm for as long as possible. In the stove top version I just cover and set aside. The temperature then slowly goes down which is fine. So, if you use a microwave, transfer to a 100 F water bath, on in a saucepan with a cover as I have done. I will explain the time factor in the next step.
In step two we will watch for the milk/starter to thicken. This is the time to place it in the refrigerator to completely solidify. In the fermentation process, the milk conversion forms lactic acid when it become yogurt. The longer it ferments, the more lactic acid and the more tangy or sharp it becomes. So, if you prefer milder and slightly more liquid yogurt, go with the 4 hours. For real zest, increase to the seven hours.
After refrigeration it is yogurt! There are many people who simply don't like the taste of plain yogurt and add honey or other sweetener. I like to add fresh fruit as well. This yogurt will last for 1 to 2 weeks in the refrigerator. This new yogurt can also serve as the starter for the next batch. Simply take out the amount needed and freeze. Thaw before use.
There is a great amount of information available on the Web, so check it out and have some fun!
There is a great amount of information available on the Web, so check it out and have some fun!
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