FERMENTED MILKS 17 
which has been thoroughly heated to destroy the bacteria already 
present. The bottles in which the milk and grains are placed should 
not be stoppered but should be protected from the dust by cloths, 
inverted cups, or plugs of cotton. They are held at or near 14° to 
16° C. (57° to 60° F.) and stirred or shaken frequently. After 8 to 
10 hours the milk is strained through cloth and put into tightly 
stoppered bottles at the same temperature as before. The bottles 
should be shaken every few hours to prevent the formation of lumps 
of precipitated casein. The kefir is ready for use at the end of 24 
hours ; if held longer than this it is advisable to keep it on ice to check 
the fermentation. The temperature at which the milk is fermented 
is important in controlling the relative amounts of alcohol and lactic 
acid. At higher temperatures the percentage of alcohol is increased, 
while as the temperature is lowered the alcoholic fermentation is 
diminished and the quantity of lactic acid formed is greater. After 
the fermentation is once started the grains may be discarded and new 
kefir made by adding one part of the fermented milk to three or four 
parts of fresh milk. In order to remove the grains the kefir should 
be strained through cheesecloth, and after thorough washing to 
remove the curd, the grains may be dried by exposure to the sun on 
pieces of blotting paper. In this condition they are said to retain 
their vitality for several years, although many of the yeasts in the 
outer part of the grain are killed by the desiccation. It may be neces- 
sary to break up the grains with the fingers. When in the wet stage 
they should not be larger than a walnut. 
The routine manner of preparing kefir does not promote the growth 
of the grains to any great extent. When it is desired to increase the 
quantity of grains, a milk of low fat content, 2 or 3 per cent, is used, 
and the product is held at 15° C. for 48 hours. The grains are then 
washed and transferred to fresh milk every 48 hours until the desired 
growth is obtained. 
Kefir grains are not easily obtained in this country, but a good 
imitation of kefir can be made by carrying on simultaneously in 
sealed bottles an alcoholic and a lactic fermentation. Better results 
can be obtained by inducing the alcoholic fermentation in buttermilk. 
In this way it is possible to avoid much of the trouble from the for- 
mation of lumps of curd. If buttermilk is made for this purpose 
from whole or skim milk, careful attention should be given to the 
time of curdling and the breaking up of the curd. This is essential 
to a smooth, creamy kefir. Ordinary bread yeast may be used for the 
alcoholic fermentation, but as this yeast does not ferment lactose it 
is necessary to add cane sugar to the milk. If buttermilk is used in 
making kefir, the following steps should be taken : 
Buttermilk may be obtained from a dealer or prepared as directed 
on page 7. The yeast is prepared by adding a half teaspoonful of 
sugar to a 6-ounce or 8-ounce bottle of boiled and cooled water. Half 
a yeast cake is added to this sugar solution and set in a warm place 
overnight. This will give an active culture of the yeast and obviate 
the necessity for adding the yeast cake directly to the milk. This 
yeast culture should be ready at the time the buttermilk is received 
or, if made at home, at the time it is curdled. 
One to one and a half per cent of sugar is added to the butter- 
milk. On the quantity of sugar added to the buttermilk will depend 
