Roger Merkel, Ph.D.
Langston University
American Institute for Goat Research
100 Success Avenue
Langston, OK 73050
ARTICLE ON SMALL SCALE PRODUCTION OF YOGURT
Here is the web page from which this article was derived:
http://biology.clc.uc.edu/Fankhauser/Cheese/yogurt_making/YOGURT2000.htm
HISTORY:
The origins of yogurt are lost in our early history, but it seems likely that it came from the nearEast, perhaps as early as 5,000 BC at much the same time that the practical arts of agriculture
were being developed in the fertile crescent of Mesopotamia. It is clear that as soon as dairy
animals were kept, milk would have been souring. While some milk spoiled because
putrefactive bacteria, occasionally, the soured milk had a pleasant, tart flavor, and was good for
consumption. At some point, someone noted that adding some of this good soured milk to
fresh milk would ensure that the milk would turn into a favorable product. This practical art,
though totally lacking in scientific understanding, became part of the culture, and was passed
down to succeeding generations.
One advantage of this product, which we now know has undergone lactic fermentation, is its
acidity, which inhibits putrefactive bacteria from growing. Thus, milk acidified with specific
bacteria are still palatable, safe to consume and will keep for much longer, even at ambient
temperatures.
Ancient Turks referred to this spontaneously fermented milk product as yoğmak meaning "to
be curdled or to thicken". To this day, yogurt is prominent in Turkish cuisine, and a staple in
diets of people many countries of the area between Asia and Europe. The longevity of the
Bulgarian and Caucasus people has been attributed to their consumption of yogurt. In the 20th
century, Bulgarian and Russian scientists (including Nobel –laureate Menchnikov) identified the
bacteria causing fermentation of yogurt as rod-shaped (Lactobacillus) and chains of spherical
(Streptococcus) bacteria.
WHAT STARTING PRODUCT CAN BE USED TO MAKE YOGURT?
Yogurt can be fermented from any kind of milk, as well as a number of vegetable “milks.” All
that is necessary is a sugar which can be fermented which these bacteria can produce into lactic
acid. A major key to success is to ensure that the only bacteria present in the warmed scalded
milk are the beneficial “lactic acid” bacteria. The acidification results in a healthful, thickened,
acidic food that will stay fresh longer than milk itself, and that contains millions of bacteria that
are welcomed by the human gut.
Yogurt has gained considerable popularity in America in recent decades, in keeping with
general trends toward organic, cultured, and nutrient-dense foods.
Yogurt can be mildly tart or quite sour, and can be anywhere between thin enough to pour to
thick enough to stand up on a plate. Yogurt contains the protein and calcium of milk as well as a
variety of vitamins. Additionally, since the process of yogurt fermentation is similar to the
process of digestion, yogurt can be easily digested.
NUTRITIONAL CONTENT
Not only does yogurt contain the same amount of protein and fat as the milk from which it is
made, it also contains calcium, riboflavin, vitamin B6, and vitamin B12. Because it is easily
digested, it offers nutrition to individuals who may have digestive problems or malabsorbtion
syndromes of a variety of descriptions.
OUTLINE OF THE PRINCIPLE STEPS IN MAKING YOGURT:
Here are the several simple principles of making good yogurt:
1) Good quality milk is scalded (95 C) to kill any pathogens of putrefactive bacteria.
2) The milk is cooled to 55 C.
3) Bacterial starter, containing live lactic acid bacteria, usually yogurt from a previous
batch, is added at the ratio of 1 part yogurt to 16 parts scalded and cooled milk.
4) The inoculated milk is poured into sterilized jars, covered, and incubated at 50 C for 3
hours, or more if greater tartness is desired.
5) The jars are chilled, and kept under refrigeration until desired. Properly made yogurt
will easily keep a month or more.
TURNNING ONE GALLON (FOUR LITERS) OF MILK INTO YOGURT:
EQUIPMENT:
Heat source: we prefer gas because of heat distribution, but electric or other source will suffice.
Large ~five gallon pot (= 20 liter) with lid
Seven Mason jars, plus a 16 ounce jar for the next starter
Eight Lids
Eight Rims
Tongs
Two cup (500 mL) measure
whisk
MATERIALS:
One gallon of fresh wholesome milk
8 ounces of fresh unalduterated yogurt (or starter purchased from a supplier)
I: STERILIZE JARS AND EQUIPMENT TO BE USED:
1) Proper sanitization is important at every stage of making yogurt. To start, the
containers in which the yogurt will be made must be sanitized. To do this, place about an
inch of water in the bottom of a large pot (a canner is being used here). Place all equipment
to be sterilized in the pot :
a) Mason jars
b) Lids
c) Rims
d) Tongs
e) Two cup (500 mL) measure
f) Canning funnel.
2)
Cover the pot and bring to a boil so that you see steam coming out from under
the lid. Boil for 10 minutes.
3)
Spread a clean cloth (here a dish towel), and unload the sterilized equipment
from the sterilizing
pot.
II. SCALD AND COOL THE MILK.
1) Meanwhile, select a 1.5 to 2 gallon stainless steel pot which features a thick aluminum
pad on the bottom to disperse the heat and prevent burning. (Alternatively, set up a
double boiler with a larger pot mostly filled with water into which the pot containing the
milk is placed. Have a lid which covers the whole assembly.)
2) Add one gallon of fresh milk to the pot. You may just about any milk: 3.5 %, 2% or
skimmed milk. More butterfat produces a richer flavored yogurt. (Reconstituted
powdered milk does not work well because the yogurt is very thin and
tasteless.)
3) Cover the pot and heat slowly to 85 C (185 F). The first time you make it, monitor the
milk to be sure it is not burning or sticking to the bottom. If it sticks, turn down the heat
and/or stir more often. If in doubt, the safest heating means is to use a double boiler as
described above). With the pot shown, we are able to have the flame on medium high
with no problems and reach 85 C in about 25-30 minutes.
4) Run a clean dish pan half full of cold, clean tap water. Carefully lower the covered 85 C
milk into the dish pan to cool. (Do not splash the cooling water into the scalded milk.)
5) Insert a thermometer into the milk to monitor the temperature. Closely watch the
temperature as the milk cools. You want a cooled temperature of 55 C, (no lower than
50 C). Stir when the temperature drops to 55 C (130 F). Once the milk is uniformly at or
below 55 C, remove from the cold water bath to the
counter.
III. INOCULATE THE SCALDED AND COOLED MILK WITH BACTERIAL
STARTER
1) For a yogurt starter, either purchase pure starter from a dealer, or purchase the freshest
pure yogurt at the store (with the expiration date farthest into the future). It should
contain only cultured milk and live bacteria. (No fruit, pectin, guar gum or other
additives). “Dannon Plain” has worked well for years.
A)
Place 1 cup of scalded and cooled milk in the sterilized two cup measure.
B)
Add enough commercial yogurt to q.s. ( fill) the two cup measure to the two cup
level.
C)
Blend the two cup contents thoroughly with a whisk.
2) Add the blended yogurt-milk starter to the scalded and cooled milk (it should still be
between 50 and 55 C) with stirring to mix
thoroughly.
3) Fill the sterilized jars with the 50-55 Cinoculated milk, using the sterilized funnel if
necessary. Immediately cover as soon as the jar is filled.
4) Alternately, with practice, one can pour the milk directly from the pot into the sterilized
jars. Again, cover immediately with sterilized
lids.
IV)
INCUBATE THE INOCULATED MILK AT 50 C
1) Heat about a gallon and a half of water to 55 C. (Part of the water can be the water
used to cool the scalded milk). Situate a “cooler” (Styrofoam, “Playmate”, etc) where it
can sit undisturbed for the length of the incubation.
2) Place the jars of inoculated milk into the cooler, and fill with the55 C water up to the
shoulders of the jars. (Do not over fill which could contaminate the lids with the water).
Check the temperature. It should now be around 50 C (up to 55 C). Close the “cooler”
and do not disturb for around three hours. After three hours, check for gelling by gently
shaking. If suitably gelled, label each jar with the date and place in the
refrigerator.
IV.
REFRIGERATE FINISHED YOGURT FOR LONG TERM STORAGE
1) Yogurt made at home is delicate and mild. If you want it more tart, incubate
longer. If you want it thicker, you may dissolve a tablespoon (15 cc) of
powdered milk per quart (liter) in the milk before scalding. Alternatively, you
could make “Greek yogurt” (see below).
2) If the properly made yogurt is refrigerated at 4 C, it will easily keep for a month
or longer.
V. MAKING “GREEK YOGURT”
1) “Greek yogurt” is all the rage these days. It is merely yogurt which has been partially
drained. To make a thicker yogurt, referred to as “Greek yogurt”:
A) Line a strainer or colander with a sterile cloth (a handkerchief sterilized by boiling
works great). Stir your yogurt well, and transfer it into the cloth. (You may save the
original jar to hold the finished “Greek”
yogurt.)
B) Pick up the four corners of the
handkerchief.
C) Suspend with a thick rubber band looped around the ends as shown, and hang to
drain for one to three hours (or more?), depending on how thick you like your Greek
yogurt. Transfer the drained yogurt back into the jar and store in the refrigerator. If
you add a teaspoon of salt/quart first, and drain it overnight, you have made labneh,
a favorite Lebanese soft cheese. Here is the webpage describing how to make
labneh and how to serve it:
http://biology.clc.uc.edu/Fankhauser/Cheese/Making_Laban/Labneh.htm
EPILOGUE:
The production of yogurt, while involving a number of steps which require careful attention, becomes
simple as you understand the reason behind each step. Of course, rigorous attention to each step is
necessary so that the quality of the final product is ensured.
USES OF YOGURT?
You may want to explore the numerous recipes which use yogurt as a central ingredient, especially in
the middle and near east. The tart and healthful contribution to these dishes is wonderful.
Finally, in recent years, we have seen increasing advertising campaigns which promote the health
benefits of “probiotic” bacteria in yogurt. We look forward to additional evidence of the health benefits
to consumption of yogurt.