OVERRUN 403 



buttermilk to test very high, amounting to from .5 to 1 per cent 

 or more, and causing a reduction of the overrun of from 1 to 3 per 

 cent or more. 



As it is difficult to correctly determine the per cent fat in 

 the buttermilk by the ordinary Babcock test, the results of the 

 test often do not show all the fat present in the buttermilk, so 

 that the operator may think that he is churning exhaustively 

 when in reality he loses much fat. For directions of testing 

 buttermilk see Chapter XXII. 



Some of the most important factors which control the ex- 

 haustiveness of churning are: Churning temperature, time held 

 at churning temperature, richness of cream, condition of cream, 

 fulness and speed of churn, size of butter granules when churn is 

 stopped, etc. For detailed discussion of these factors the reader 

 is referred to Chapter X on "Conditions Influencing the Churn- 

 ability of Cream," also Chapter VII on " Neutralization" and 

 Chapter VIII on "Pasteurization." 



Other Mechanical Losses Which Tend to Reduce the Over- 

 run. Frequently the low overrun is found to be due to exces- 

 sive foaming of the cream in the vats. The cream foam usually 

 contains a high per cent of fat. It is flushed out of the vats 

 with difficulty only, and often much of it goes into the sewer. 

 Efforts to thoroughly flush this foam out of the vats into the 

 churn require excessive amounts of water, usually warm water. 

 This in turn dilutes the cream and increases the amount of but- 

 termilk, thus augmenting the volume of buttermilk and with it 

 the amount of fat lost. The thinning of the cream in itself 

 causes a higher per cent of fat in the buttermilk. Furthermore, 

 the cream in the churn is thus warmed above the intended churn- 

 ing temperature, by the copious rinsing down of the foam with 

 warm water, which makes for less exhaustive churning. 



In most cases the excessive foaming of the cream in the vats 

 is due to too high a speed of the coils, whipping air into the 

 cream. This is especially 'the case when the vat is not full and 

 the coil is only partly covered with the cream. Reducing the 

 speed of the coil generally diminishes and often stops the foam- 

 ing entirely. The larger the coil the slower should be its speed. 

 The proper speed for a 24-inch coil is about 35 to 40 revolutions 

 per minute, for a 29-inch coil 28 to 30 revolutions per minute. 



