APPLICATION OP REFRIGERATION TO HANDLING OP MILK. 81 
brine is circulated, and the temperature is controlled by regulating 
the flow. The coils are rotated at a constant speed, thereby insuring 
even temperature throughout the mass of cream. With an arrange- 
ment of this kind the temperature of the cream is raised to 140° and 
allowed to stand for 30 minutes, when it is cooled quickly to about 
65° by circulating cold water through the coils. The cream is allowed 
to stand at this temperature until it is ripened. The temperature 
must again be reduced to 52° to 60° before the ripened cream is run 
into the churn. This latter reduction of temperature of about 10° is 
accomplished by low-temperature brine or ice water. 
The proper churning temperatures also vary, but in summer from 
52° to 54° is considered to be an average, while in the winter, the 
churning temperature rises to about 56° to 60°. 
The term "starter" is used to designate a quantity of milk in 
which lactic acid-forming bacteria have been cultivated until it 
contains large quantities. This starter is added and seeds the cream 
with great numbers of these cultivated bacteria, which by their 
growth cause the acid formation to progress rapidly and in a more 
definite manner than without the addition of the starter. 
In the preparation of the starter a quantity of good skimmed 
milk is taken and heated to a temperature of 185° to 190° and allowed 
to stand for 30 minutes, after which it is cooled down to. 70° or 80°. 
To this milk is added the mother starter, which is a pure culture 
of the desired bacteria, in sufficient quantity to sour the skimmed 
milk in about the desired time. In order to develop the proper 
flavor, the perfect control of the temperature of the starter milk is 
necessary. Where the starter is made every other day it is pre- 
served by holding at a temperature of 50° or below. The amount 
of starter usually required is one gallon for every 10 or 15 gallons of 
cream. The cooling of the starter from the pasteurizing temperature, 
185° to 190°, is usually done by circulating well water through the 
jacketed space surrounding the starter can; consequently, mechanical 
refrigeration is only required to preserve the starter in storage. 
An ample supply of pure cold water for working the butter is very 
desirable. The average temperature of well water, especially in the 
South, is too high for washing butter; consequently it becomes 
necessary to cool the water to a temperature sufficiently low for this 
work. The temperature of the water used in washing the butter 
depends to a certain extent upon the character of the butter. In 
summer weather, wash water at a temperature of about 52° to 56° 
is considered satisfactory, while in winter, the temperature may be 
as high as 60° to 62°. It may be generally stated that the tempera- 
ture of wash water should not vary more than from one to three 
degrees below the temperature of the buttermilk. 
40083°— Bull. 98—14 6 
