24 BULLETIN 319, U. S. DEPARTMENT OF AGRICULTURE. 
In making yogurt on a large scale the process is not essentially 
different except that it is advisable to carry a small culture, about 
1 quart, to inoculate the milk to be made into buttermilk. Every 
precaution should be taken to maintain the purity of the culture. 
It is advisable to carry duplicate cultures independently so that a 
good one will always be available. 
Expensh T e outfits for making fermented milks are on the market, 
but while they may be convenient they are by no means essential. 
For the smaller dairy the following procedure will probably be 
found satisfactory : 
(1) Propagate a small culture from day to day as indicated in the 
directions given above. 
(2) Carry in a similar way a culture of the ordinary sour-milk 
organism, which may be obtained from many of the commercial 
laboratories. 
(3) Thoroughly pasteurize the milk to be fermented. If a small 
quantity — 5 to 10 gallons, for instance — is to be made, it may be 
done by holding a can of milk in a tub or vat of water heated by a 
steam hose. If a larger quantity is made, one of the starter cans 
used in creameries will be found convenient. These are essentially 
cylindrical vats with mechanical stirrers and a jacket which can be 
filled with steam for heating or water for cooling. The milk should 
be held at a temperature of at least 180° F. for not less than 30 
minutes. 
(4) Cool the milk to about 100° F. Draw off one-half and inocu- 
late it with the culture obtained in (2). Inoculate the remaining 
half with the bulgaricus culture obtained in (1). The amount to be 
added will depend on the quantity of milk to be fermented, the time 
at which it is desired to have it curdled, and the temperature main- 
tained during the fermentation. This can best be determined by ex- 
perience. One pint should be sufficient for any amount between 10 
and 20 gallons. 
(5) The milk inoculated with (2) may be held at ordinar}^ room 
temperature. Precautions must be taken to hold that part inocu- 
lated with the bulgaricus culture at a temperature of 90° to 100° F. 
for several hours. If the milk is in cans it may be set in a tub of 
warm water. A large volume of milk in a warm room will maintain 
the proper temperature. 
If one is unable to hold the milk at the desired temperature, the 
amount of culture inoculation should be increased. 
(6) When the milk has curdled, which should be in 10 or 12 hours, 
mix the two lots thoroughly by churning or stirring together, 
bottle, and put on ice to check the acid formation. 
