CHURNING. 433 



If the temperature at which the butter is churned and worked 

 be too high, very large percentages of water (up to 50 per cent.) 

 may be found ; this may be reduced very materially by cooling 

 the butter for several hours and re-working. 



Various substances rennet, pepsin, sodium carbonate, etc. 

 have been used to increase the yield of butter ; this effect is 

 attained by increasing the water contained in the butter. 



An article is sold under the name of " milk blended " butter, 

 which is made by working milk into butter ; the water is thereby 

 raised to 22 to 26 per cent., and the solids not fat are correspond- 

 ingly increased. 



Casein, to which sufficient alkali is added to make it soluble, 

 and often containing a little gelatine, condensed milk, and milk 

 powders are also sometimes added to butter. 



Preservatives in Butter. Besides salt, various other sub- 

 stances are used as preservatives ; the most usual are mixtures 

 of borax and boric acid, though formalin, salicylates, sulphites, 

 fluorides, and potassium nitrate have also been employed. 



Chemical Control of Churning Operations. The fat in the 

 buttermilk from each churning should be estimated. Usually 

 less than 1 per cent, of fat may be considered satisfactory, but 

 if sweet cream be churned it is difficult always to keep within 

 this limit. Any percentage of fat above 2 must be considered 

 unsatisfactory, and the cause should be enquired into. This 

 may be due to the use of cream which is too thick, mixtures of 

 cream of different consistency and age, too high a temperature, 

 or too rapid churning. 



The fat in the cream to be churned should also be estimated. 

 It has been found that cream containing from 25 to 30 per cent, 

 of fat gives the most satisfactory results. If the cream contains 

 more than 40 per cent, of fat, the buttermilk is very high in fat, 

 and a larger percentage loss is obtained. 



The weight of fat in the butter plus the weight of fat in the 

 buttermilk should come within 2 per cent, of the weight of fat 

 in the cream used. If a larger difference be found, a needless loss 

 of fat is taking place, and the cause of this should be ascertained. 



Table CLI. gives the weight in pounds of butter which may 

 be expected to be produced on churning cream varying in per- 

 centage of fat from 15 to 50. 



An approximation to the amount of butter in pounds that 

 may be obtained from milk by churning the separated cream 

 can be obtained by subtracting 0-1 from the percentage of fat, 

 multiplying the difference by j^, and by the number of gallons 

 of milk. 



The Use of Starters in Butter-making. The acidity of 

 the cream should be determined before churning, if ripened 



28 



