FERMENTED MILKS 15 
KEFIR 
Fermented milks have evidently been extensively used for many 
centuries by the people of southern Russia, Turkey, the Balkan coun- 
tries, and their neighbors. The natives have no records and few 
traditions of the origin of the milks they use, and it is probable that 
their preparation and use developed gradually by accident and cumu- 
lative experience. One of the first of the fermented milks known to 
Europeans was the kefir, made from the milk of sheep, goats, or 
cows in the Caucasus Mountains and neighboring regions. Kefir 
differs from most of the fermented milks of the Mediterranean coun- 
tries in that it is made from a dried preparation and contains con- 
siderable quantities of alcohol and gas. Kefir is made by many tribes 
under varying names, as " hippe," " kepi," " khapon," " kephir," 
" kiaphir," and " kaphir," all of which are said to come from a com- 
mon root signifying a pleasant or agreeable taste. 
For a large part of their food the mountaineers of the Caucasus 
depend on kefir, which they prepare in leather bottles made from the 
skins of goats. In the summer the skins are hung outdoors, either 
in the sun or in the shade, according to the weather, but in winter 
they are kept in the house. The bags are usually hung near a door- 
way, where they may be frequently shaken or kicked by each 
passer-by. Fresh milk is added as the kefir is taken out, and the 
fermentation continues. During this process foreign bacteria mingle 
with the essential bacteria of the seeds or grains, which are small, 
yellowish, convoluted masses in the kefir, and abnormal and fre- 
quently disagreeable flavors may result. In order to prevent the 
escape of gas when the milk is drawn off, a string is tied around 
the neck of the leather bottle, so that the small part wanted for use 
is held between the stricture and the opening. In the villages and 
the low country kefir is made in open earthen or wooden vessels, 
and most of the gas escapes. 
The grains in kefir consist of a central filament of two parts, of 
which the outer spreads out, forming the convoluted polyplike ex- 
terior. These parts are built up one upon another, giving the large 
grains a corallike appearance. The central part is made up of a 
mass of bacterial threads. In the outer layer yeast cells are found 
mingled with the bacteria. When the grains are added to milk they 
swell and increase in size by forming new grains. At the begin- 
ning of the fermentation they settle to the bottom, but in a short 
time they are carried to the surface by attached bubbles of gas. If 
the fermentation is active, a thick layer will be formed on the sur- 
face, but when shaken or stirred this layer settles again to the 
bottom. 
The biology of kefir was studied by Kern (4-7) in 1881, but, owing 
to the faulty technique of that day, his descriptions are evidently 
erroneous. 
Freudenreich (28) describes four organisms that he isolated from 
kefir grains. One of these was a yeast which he designated Sac- 
charomyces kefir; this he found to grow best at 22° C. (72° F.), but 
not at all at 35° C. (95° F.). It ferments maltose and cane sugar 
but not lactose. It gives a peculiar flavor to milk but causes no 
fermentation. The cells are oval, 3 to 5 microns by 2 to 3 microns. 
It is not identical wfch the ordinary beer yeasts. Two of the organ- 
