Yogurt Making

Yogurt is a fermented milk product which originated in Turkey in which a mixed culture of Lactobacillus bulgaricus (or occasionally L. acidophilus ) and Streptococcus thermophilus produce lactic acid during fermentation of lactose. The lactic acid lowers the pH and makes it tart and causes the milk protein to thicken. 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:

  1. Good sterile technique (i.e., proper cleansing and heat treatment of glassware, and keeping out unwanted bacteria)
  2. Proper incubation temperature. Lactobacillus is killed if exposed to temperatures over 55oC (130o F), and does 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.)
  3. 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. 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.

SUPPLIES

EQUIPMENT
  • 1 gallon fresh milk (whole milk makes richer flavored yogurt, skim milk makes it non-fat)
  • starter: 1 cup Dannon Plain yogurt, very fresh I prefer Dannon Plain, made purely with milk and culture. 

 
  • Double boiler (or heavy pot) with lid,  capacity 1+ gallon 
  • Four quart jars with lids, sterilized in boiling water 
  • One 8 oz jar with lid, sterilized in boiling water. 
  • Candy thermometer, reading range = -10 to 110oC (0 to 225 oF) 
  • 1 medium sized cooler  (such as a "Playmate" or styrofoam with close fitting lid) 
  • (A gas oven with pilot may work if monitored closely).

PROCEDURE

1:  Sterilize jars and lids which will be used to make the yogurt.  Place in a 5 gallon pot with an inch of water in the bottom. For more firm yogurt, add 4 tblspn powdered milk to the gallon of milk prior to heating

9:  Place one cup of the scalded and cooled milk in a two cup measure.

2:  Cover and bring to boil. Boil for ten minutes.  Turn off heat, do not remove lid.

10:  Add enough fresh, uncontaminated yogurt to bring the level up to two cups.

3:  Use a pot with a thick bottom to scald the milk.  A double boiler may be used.

11:  Stir to blend the yogurt starter into the scalded and cooled milk until homogenious.

4: Add one gallon of milk to the pot.  You may use whole, 2% or skimmed milk. Here I am using my home grown goat's milk.

12:  Inoculate - Add the yogurt-milk slurry slowly to the  50 C scalded and cooled milk with stirring.  Stir very well to thoroughly distribute the yogurt starter.

5:  Warm the milk over a medium fire (not so hot that it burns on the bottom).

13:  Once throughly mixed, distribute the inoculated milk to the sterilized jars, filling to the neck.  Cover immediately with sterile tops.  Tighten well.

6:  Heat until the temperature of the milk is 85-90 C (185-195 F).  It is not necessary to boil, and do not let boil over! 

14:  Incubate - Warm a gallon of fresh clean water to 55 C, pour into a clean cooler.  Place in a warm location.  Carefully set the jars of inoculated milk in the water so the bottom of the lids are above the water.

7:  Place the still covered pot in a pan of clean cold water to cool it down.

15:  Check to see that the water in the cooler is not below 50 C (122 F) or above 55 C (130 F).

8:  Cool the milk to 50 to 55 C (122-130 F).  Remove the pot of scalded and cooled milk from the cooling bath.

16:  Close the cooler, place in warm place and let sit undisturbed for three hours.  If the starter was active and the temperature correct, the yogurt will have gelled:

For more firm yogurt, add 4 tbspn powdered milk to the gallon of milk prior to heating (step 3). 

Recently, I have switched to a two gallon stainless pot with a heavy pad of aluminum on the bottom. It considerably simplifies heating the milk. So long as you heat it to 85-90oC (185-195o F) without burning, that is what is required. Once the milk has been scalded and cooled, you can even add the starter directly to the pot, and make the yogurt in the pot. It is better aseptic technique.

Yogurt has many uses

My favorites include:

 

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