INTRODUCTION Yogurt
Yogurt is a fermented milk product which was apparently broght to Turkey by the mongols millenia ago. It is produced by adding a "starter" of active yogurt containing a mixed culture of Lactobacillus bulgaricus (or occasionally L. acidophilus ) and Streptococcus thermophilus. These produce lactic acid during fermentation of lactose. The lactic acid lowers the pH, makes it tart, causes the milk protein to thicken and acts as a preservative since pathogenic bacteria cannot grow in acid conditions. The partial digestion of the milk when these bacteria ferment milk makes yogurt easily digestible. In addition, these bacteria will help settle GI upset including that which follows oral antibiotic therapy by replenishing non-pathogenic flora of the gastrointestinal tract.
Several factors are crucial for successful yogurt making:
* a. good sterile technique (i.e., proper sterilization and cooling of the milk, proper cleansing and heat treatment of glassware, and keeping out unwanted bacteria)
* b. proper incubation temperature. Lactobacilli and Streptococcus thermophilus are thermophilic bacteria, meaning they prefer elevated temperatures for growth. At such temperatures (50 C, in this case) pathogenic or putrifactive bacteria are inhibited. However, even these thermophilic bacteria are killed if exposed to temperatures over 55oC (130o F), and do not grow well below 37oC (98oF). We will incubate at 50oC, a temperature on the high side of its preferred growth temperature (122oF), a temperature which inhibits the growth of pathogenic bacteria. (Note that many recipes call for cooler temperatures than this. We find the results less dependable when incubation temperatures are lower.)
* c. protection of the starter from contamination. Do not open the starter (either Dannon Plain yogurt, or 8 oz starter from the previous yogurt batch) until you are ready to make the next batch.
Yogurt is preserved by its acidity which inhibits the growth of putrefactive or pathogenic bacteria. With lids intact, this yogurt will keep at least a month or two in the refrigerator. After that time, especially if your refrigerator is on the "warm" side, a layer of non-pathogenic white mold may form on the top. Merely lift off the mold with a fork, discard, and use the yogurt for cooking.
Baked goods will rise well when yogurt is used, again due to its acidity. Use yogurt as part or all of the liquid in cakes, waffles, pancakes and muffins, and cut down on the amount of baking powder. The thickness of yogurt helps to hold up the baking batter.
Yogurt is an excellent dish by itself, but is valuable in its many other uses
The following recipe makes four quarts of yogurt. If you would like to make 2 quarts, here is the recipe . The following instructions may seem overly detailed, but I believe that the detail increases your chance of successful yogurt.