Yogurt Making Illustrated

	YOGURT MAKING ILLUSTRATED David B. Fankhauser, Ph.D. Professor of Biology and Chemistry U.C. Clermont College Batavia OH 45103
You can use commercial yogurt as your starter.	~1980, rev. 17 December 1993, 5 Dec 98, 11 Dec 98, 18 Apr 99, 20 Apr 99, 3 Jan 00, 7 Sept 00 This page has been accessed times since 1 Sept 2000.	Use a "cooler" for an incubator

Yogurt is a fermented milk product in which a mixed culture of Lactobacillus bulgaricus (or occasionally L. acidophilus) and Streptococcus thermophilus which produce lactic acid during fermentation. This lowers the pH and makes it tart. 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 cleansing and heat treatment of glassware, and keeping out unwanted bacteria)

b. proper incubation temperature. Lactobacillus is killed if exposed to temperatures over 55^oC, and does not grow well below 37^oC. We will incubate at a temperature on the high side of its preferred growth temperature, a temperature which inhibits the growth of pathogenic bacteria.

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 spoilage bacteria. With lids intact, this yogurt will keep at least a month or two in the refrigerator. After that time, a layer of non-pathogenic white mold may form on the top. After this is removed, the yogurt is still suitable for cooking.

Baked goods will rise well when yogurt is used due its acidity. Use it as part or all of the liquid in cakes, waffles, pancakes and muffins, and cut down on the amount of baking powder.

Yogurt is an excellent dish by itself, but is valuable in its many other uses. See additional suggestions below.

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.
Click on a thumbnail image to see the full-sized image

SUPPLIES EQUIPMENT

1 gallon fresh milk
1 cup Dannon Plain yogurt (starter)
(I prefer Dannon Plain, made purely with milk and culture: it WORKS.)
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, very clean and sterile
candy thermometer, reading range = -10 to 110^oC (0 to 225^oF)
1 medium sized cooler
      (such as a "Playmate" or styrofoam with
        close fitting lid)
      (A gas oven with pilot can work if monitored).

Procedure

	1) Set up a double boiler which will hold a little more than one gallon. Here I improvise a double boiler by adding 3/4 inch water to a pot which will accept the one gallon primary pot.
	2) Insert the one gallon primary pot into the secondary (water-containing) pot.
	3) Add 1 gallon of cold, fresh milk to the primary pot, insert a thermometer and cover.
	4) Turn on heat to bring water in secondary pot to boil. The temperature of the cold milk at the beginning of the heating is around 4^oC.
	5) Continue heating over medium fire until the temperature reaches 85-90^oC (185^oF). If you are using a double boiler, you will not need to stir the milk, but be certain that you do not run out of water in the secondary pot. If you are using a heavy pot, stir frequently to prevent sticking. Keep covered when not stirring.
	6) Once the milk has reached 85^oC, turn off the fire, remove the covered pot of hot milk with hot pads and carefully lower it into a pan of clean cool water. Stir occasionally (always replace lid) until the temperature is just below 55^oC.
	7) While the milk is cooling, measure out 1 cup live yogurt into a two cup measure. For starter, you may use either unopened yogurt from your previous batch, or a freshly purchased cup of Dannon Plain Yogurt.
	8) Stir up yogurt starter with a clean fork, add an equal volume of 55^oC milk, stir thoroughly.
	9) Be certain that the temperature of the cooled milk is 55^oC (125^oF).
	10) Stir the suspended starter into the gallon of 55^oC milk to inoculate the milk with the bacteria. The temperature of the mixture should drop to around 50^oC.
	11) Whisk the mixture to blend thoroughly.
	12) Immediately distribute the (still warm) inoculated mixture into the four quart bottles, plus the smaller 8 oz jar. Cover immediately with the sterile lids. The 8 oz jar will serve as your starter for your next batch of yogurt.
	13) Place filled bottles in cooler "incubator," add enough 50^oC (120^oF) water so that bottles are surrounded, but the water is well below the lid rims. The starter jar will have to be placed on a support to keep its lid above the water.
	14) Place "incubator" in warm location. Do NOT disturb, or the yogurt will not gel properly.
	15) The yogurt will be finished in 3 hours, provided its temperature does not drop below 37^oC (98^oF). (Note in the picture that the temperature has dropped from 50^oC to 42^oC.) Label each jar with the date, and refrigerate at 4^oC until needed. To keep the starter free of contamination, do not open the 8 oz starter jar until you are ready to make the next batch.
	16) The resulting yogurt will be mild and delicate. It will easily keep a month under these conditions. If you want yogurt that is more tart, incubate longer and maintain the temperature near 50^oC by adding hot water to the "incubator."

For more firm yogurt, add 4 Tbl powdered milk to the gallon of milk prior to heating (step 3). Either whole or skimmed milk may be used, but whole milk makes richer yogurt.

YOGURT HAS MANY USES:

My favorite include:

In place of sour cream. Add dollops:
    to baked potatoes
    on rice dishes
    on bowls of soup (especially lamb stew, chili or borscht)
    with hot chili (works as an oral fire extinguisher too!)
In cucumber-yogurt soup (fabulous summer dish)
As a liquid (or portion of the liquid) in baking soda-raised breads, waffles and pancakes
As labneh, a Lebanese soft cheese, (easy yogurt cheese). It can be made by hanging yogurt in a clean cloth, permitting the whey to drip into a bowl. Add salt to taste. It is delicious served with pulverized spearmint and olive oil as a dip. Follow the link to a page on how to make labneh.
As a starter for cheese
As a starter for yogurt (see above for how to do this)
Check any Middle Eastern cookbook for a variety of uses.

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	SUPPLIES	EQUIPMENT
	1 gallon fresh milk 1 cup Dannon Plain yogurt (starter) (I prefer Dannon Plain, made purely with milk and culture: it WORKS.)	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, very clean and sterile candy thermometer, reading range = -10 to 110^oC (0 to 225^oF) 1 medium sized cooler (such as a "Playmate" or styrofoam with close fitting lid) (A gas oven with pilot can work if monitored).