172 SCIENCE AND PRACTICE OF DAIRYING. 



often advertised, contains, as its chief constituent, sodium carbonate, and 

 perhaps also alum or salt or saltpetre or annatto, and consequently can 

 only act as a neutralizer of the acid, or impart to the butter a higher 

 colour. Among the harmful substances added occasionally, with male- 

 volent intent, to a liquid to be churned, are soap-lye, sal ammoniac, even 

 small quantities of which retard or render churning quite impossible. 

 Sugar-gum, lime, spirits, meal, crumbled bread, to which a harmful action 

 has been also ascribed, have no bad effect if added in small quantities. 



If in winter the room in which churning is to be carried on is not 

 warm, or in summer is not cool enough, the churn should be cooled or 

 heated, before churning, with hot or cold boiled water. 



If the butter has to be coloured, the butter colour should be measured 

 in proper proportion, and cautiously mixed with the fluid in the churn 

 immediately before churning is commenced, so that none of the colour may 

 come into contact with the wood of the churn and thus be lost. 



A daily register of the initial and final temperature of the liquid and 

 the length of time of churning ought to be kept, and this register ought to 

 furnish a useful table of reference for judging of the speed of motion. 



So far as the author is aware, it has not been attempted to churn daily 

 and regularly in one churn more than 400 kilos, of liquid. 



92. Churning of Sour Cream. Sour cream is comparatively more 

 easily churned, and yields, when the souring has been properly done, 

 a butter which possesses the best keeping properties. The tempera- 

 ture at which churning begins varies, under ordinary conditions, 

 between 13'75 and 17*50 C. In large dairies the Holstein churn of 

 improved construction is almost exclusively used, and the churn is 

 worked at the rate of from 110 to 120 revolutions per minute. 

 The quantity of cream which is churned in this churn must be at 

 least large enough to stand 10 centimetres above the lower cross- 

 piece of the fly-wheel of the churn, and must not be, on the other 

 hand, so large that it stands more than a similar height above that 

 point. During churning, which should be completed in from 30 to 

 at the most 45 minutes, the temperature of the cream ought not to 

 be allowed to rise higher than from 1 to at most 2'5 C. 



93. Churning of Sweet Cream. Butter made out of perfectly 

 sweet faultless cream possesses the pure taste of butter, free of all 

 foreign flavours, and is the finest butter which can be made. Since, 

 in churning sweet cream, the souring of cream, the development of 

 which is attended with so much labour, inconvenience, and uncer- 

 tainty, is quite unnecessary, it is highly desirable, from a practical 



