Roger Merkel, Ph.D.
Langston University
American Institute for Goat Research
100 Success Avenue
Langston, OK 73050
How milk was first cultured into yogurt remains a mystery. Analysis of the L. delbrueckii
subsp. bulgaricus genome indicates that the bacteria may have originated on the surface of a
plant.[3] Milk may have become spontaneously and unintentionally infected through contact with
plants, or bacteria may have been transferred via the udder of domestic milk-producing
animals.[4]
There is evidence of cultured milk products in cultures as far back as 2000 BCE[citation needed]. In
the records of the ancient culture of India and Iran, yogurt is mentioned by 500 BCE. In ancient
Indian records the combination of yogurt and honey is called "the food of the gods".[5] Persian
traditions hold that "Abraham owed his fecundity and longevity to the regular ingestion of
yogurt".[6]
The oldest writings mentioning yogurt are attributed to Pliny the Elder, who remarked that
certain "barbarous nations" knew how "to thicken the milk into a substance with an agreeable
acidity".[7] The use of yogurt by medieval Turks is recorded in the books Diwan Lughat al-Turk
by Mahmud Kashgari and Kutadgu Bilig by Yusuf Has Hajib written in the 11th century.[8][9]
Both texts mention the word "yogurt" in different sections and describe its use by nomadic
Turks.[8][9] The earliest yogurts were probably spontaneously fermented by wild bacteria in goat
skin bags.[10]
Another early account of a European encounter with yogurt occurs in French clinical history:
Francis I suffered from a severe diarrhea which no French doctor could cure. His ally Suleiman
the Magnificent sent a doctor, who allegedly cured the patient with yogurt.[11][12] Being grateful,
the French king spread around the information about the food which had cured him.
Until the 1900s, yogurt was a staple in diets of people in the Russian Empire (and especially Central Asia
and the Caucasus), Western Asia, South Eastern Europe/Balkans, Central Europe, and India. Stamen
Grigorov (1878–1945), a Bulgarian student of medicine in Geneva, first examined the microflora of the
Bulgarian yogurt. In 1905, he described it as consisting of a spherical and a rod-like lactic acid bacteria. In
1907, the rod-like bacterium was called Bacillus bulgaricus (now Lactobacillus delbrueckii subsp.
bulgaricus). The Russian Nobel laureate biologist Ilya Ilyich Mechnikov (also seen as Élie Metchnikoff),
from the Institut Pasteur in Paris, was influenced by Grigorov's work and hypothesized that regular
consumption of yogurt was responsible for the unusually long lifespans of Bulgarian peasants. Believing
Lactobacillus to be essential for good health, Mechnikov worked to popularize yogurt as a foodstuff
throughout Europe.
The word is derived from Turkish: yoğurt,[30] and is related to the obsolete verb yoğmak "to be curdled
or coagulated; to thicken"
Originally a simple fermented dairy product, yogurt now has many variations
and personalities. It can be thin and runny, or thick and firm. It can be made
from cow milk, goat milk, sheep milk, nut milk, soy milk, rice milk, and from
numerous other creamy substances. In some countries the milk of buffalo,
horses, yaks, or camels is used.
For most of this discussion, we’ll refer to yogurt in its original form: a
fermented dairy milk. This was how yogurt was first developed, and most of
the yogurt in the world is made this way.
Essentially yogurt is the product of beneficial bacteria fermenting milk and
turning it into a thickened, acidic food that will stay fresh longer than milk
itself, and that contains millions of bacteria that are welcomed by the human
gut.
The History of Yogurt
The word yogurt comes from a Turkish word meaning to curdle or to thicken.
Today it is spelled yogurt, yoghurt, or yogourt, with yogurt being the most
common American spelling.
It’s probable that the earliest yogurt was made by accident in Mesopotamia
around 5,000 BC, when milk-producing animals were first domesticated. The
milk was likely stored and transported in bags made from the stomachs of
these animals, and the digestive juices and bacteria in the stomach linings
made the milk coagulate and become acidic. Not only was it a new and
interesting food, but the acidity and helped to keep it edible for longer than if
it had just sat out in a bowl or jar.
There is also some evidence of yogurt being used as a cleaning product and
a beauty lotion as early as 2000 BC. The acidity of the yogurt helps clean
away dirt and rust, and also helps clear away dead skin and nourish healthy
skin cells.
Yogurt was a popular food in the Middle East for thousands of years, and has
been a staple of the Eastern European diet. It’s now eaten throughout the
world, as a main course, a snack, an ingredient in many recipes, and a
condiment. It has gained considerable popularity in America in the last forty
or fifty years, in keeping with general trends toward organic, cultured, and
nutrient-dense foods.
Yogurt can be mildly tart or quite sour, and can be thick enough to stand up
on a plate, or thin enough to pour, or anywhere in between. It contains
protein and calcium as well as a variety of vitamins. Additionally, the process
of yogurt fermentation is very similar to the process of digestion, so it can
be easily consumed.
Many people eat yogurt plain, while others prefer to mix it with fruits or
vegetables, or to add flavors or sweeteners. It is used in a variety of recipes
as a flavor enhancer or leavening, and frequently enjoyed as a refreshing
drink.
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. While numerous claims have been made regarding the health
benefits and digestibility of yogurt, we don’t comment on medical, health, or
nutritional qualities of our products. However, a great deal of research on
the subject is readily available on the Internet and in dozens of books.
1: Sterilize jars and lids which will be used to make the yogurt. Place in a 5 gallon pot (here we are using
a canner) with an inch of water in the bottom.
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.
Note the thick pad on the bottom of this pot. Alternatively, a double boiler may be used. It is not
necessary to boil them ilk. This gives the milk a "cooked" flavor, and increases the probability that it will
burn on the bottom or boil over.
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. (No hotter--you will
kill the bacteria in the starter.) Stir very well to thoroughly distribute the yogurt starter.
5: Heat the milk slowly over a medium fire (not so hot that it
burns on the bottom). I am using a medium hot fire here with my thick bottomed pot.
13: Once throughly mixed, distribute the inoculated milk to the sterilized jars, filling to the neck. Cover
immediately with sterile tops. Tighten well.
6: Scald 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...what
a mess! (Many claim success leaving out this step. But... results may work, but interemittently...)
14: INCUBATE:
Warm a gallon of fresh clean water to 55 C, pour into a clean cooler. Place in a warm location. (It
should cool to 50 C or below once the cooler is warmed up.) 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 close to 50 C (122 F). Above 55 C (130 F) kills the
bacterial inoculum.)
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:
1) Place about an inch of water in the bottom of a in a large pot (a canner is being used here).
Place equipment to be sterilized in the pot : Mason jars, lids, rims, tongs, two cup measure and a
canning funnel.
2) Bring to a boil so that you see steam coming out, boil for 10 minutes.
3) Spread a clean dish towel, and unload the sterilized equipment from the sterilizing
pot.
4) Select a 2 gallon stainless steel pot which features a thick aluminum pad on the bottom to
disperse the heat and prevent
burning.
5) Add one gallon of fresh milk to the 2 gallon pot. You may use 3.5 %, 2% or skimmed milk. More
butterfat produces a richer flavored
yogurt.
6) Cover the pot and heat 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 is, turn down the heat or stir more often, or use a
double boiler. With the pot shown, I am able to have the flame on medium high with no
problems and reach 85 C in about 25-30 minutes.
7) Run a dish pan half full of cold tap water, and place the covered hot milk in it to cool.
8) Insert a thermometer to monitor the temperature. Stir when the temperature drops to 55 C
(130 F). Once the milk is uniformly just below 55 C, remove from the cold water bath to a
counter.
9) For a yogurt starter, purchase the freshest pure yogurt at the store which contains only cultured
milk and live bacteria. Dannon Plain has worked well for years. Place 1 cup of scalded and
cooled milk in the sterilized two cup measure, and add enough commercial yogurt to fill to the
two cup level. Blend thoroughly with a whisk.
10) Add the blended yogurt starter to the scalded and cooled milk (it should still be between 50 and
55 C) with stirring to mix
thoroughly.
11) Fill the sterilized jars with the inoculated milk. Immediately cover as soon as the jar is filled.
Here we are using a funnel.
12) Alternately, with practice, one can pour the milk directly from the pot into the
jars.
13) 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” where you wish to perform the incubation. Place the jars
of inoculated milk into the cooler, and fill with 55 C water up to the shoulders of the jars. (Do
not contaminate the lids with the water). Check the temperature. It should now be around 50
C. Close the “cooler” and do not disturb for around three hours. After three hours, gently shake
to see if the milk has gelled. If so, label with the date and place in the
refrigerator.
14) Yogurt made at home is delicate and mild. If you want it more tart, incubate longer.
15) “Greek yogurt” is all the rage these days. It is yogurt that has been partially drained. To make
Greek yogurt, line a strainer or colander with a clean cloth (a handkerchief sterilized by boiling
works great), and transfer your yogurt into it. (Save the
jar.)
16) Pick up the corners of the
handkerchief.
17) Suspend with a thick rubber band looped around the ends and hang to drain for one to three
hours, depending on how thick you like your Greek yogurt. Transfer the drained yogurt back
into the jar and store in the
refrigerator.