PASTEURIZATION 105 



causes the cream to circulate through the machine in a 

 thinner layer than when the speed is low. He says that 

 the capacity of the pasteurizer is increased 8 to 10 per 

 cent when using dry steam as a heating medium instead 

 of hot water. It should also be noted that when water 

 is used there is much vibration when it boils, and that this 

 is rather hard on the pasteurizer. It is especially in- 

 jurious to the soldered joints. The amount of injury 

 depends largely on the construction of the machine and on 

 the way in which it is operated. Farrell says further that 

 the steam and water connection to the ripener and vat 

 pasteurizer should be sufficiently large to admit steam 

 and water fast enough for fast heating and rapid cooling. 

 He adds that it should not require more than twenty to 

 thirty minutes to heat a vat of cream and a little longer 

 to cool it. 



Sour cream. — • In large creameries where a fairly large 

 quantity of sour cream is handled, and with the continuous 

 method of pasteurization, a fore-warmer may be employed 

 to good advantage. The cream should be heated in this 

 fore-warmer, which is a small vnt with a heating device, 

 to 100° to 120° F., where it should be held for a few minutes 

 before it goes to the pasteurizer. This prevents foaming in 

 cold weather, increases the capacity of the pasteurizer, 

 and the mixing and heating lessens the danger of the cream 

 curdling in the pasteurizer. 



Thin cream. — Thin cream is often the source of diffi- 

 culty in pasteurization. In many creameries the cream 

 becomes " mealy " after it is pasteurized if it is sour and 

 low in fat-content. The " mealy " condition is due to 

 coagulation of a small amount of the serum of the cream. 

 When the cream is thin, which means that the percentage 

 of serum is high, even a low acidity is likely to cause some 



