302 ILLINOIS STATE DAIRYMEN'S ASSOCIATION 



suggest that the sweet cream be ripened with a good starter be- 

 fore the pasteurized sour cream is added, or, still better, the 

 sweet and sour cream can he ripened and churned separately, 

 though with a small run this is hardly practicable. 



If the sweet and sour cream is mixed when received, it 

 should be ripened for 30 minutes to two hours before it is pas- 

 teurized. This allows the sweet curd to be acted upon by the 

 lactic acid in the sour cream, making the whole mass of an 

 even acid content. By ripening in this way, the cream would 

 be beyond the curdling point and may be pasteurized without any 

 trouble. The length of time cream should be allowed to stand 

 before pasteurizing will depend upon the percentage of sweet 

 and sour cream, as well as on the temperature at which the cream 

 is held. The best guide in these matters is experience, and the 

 buttermaker should change his methods to conform with the con- 

 ditions under which he is working. 



We are ready to agree with any buttermaker that this rip- 

 ening of sweet and sour cream before pasteurization is not go- 

 ing to help the quality. Especially is this true if the sour cream 

 is of poor quality, and we recommend this method only where it 

 is impossible to grade the cream and handle it separately. 



When the vat method is used in pasteurizing sour cream, the 

 cream should first be heated to about 115 degrees F., and then 

 held at or near this temperature for a short time. The temper- 

 ature should then be raised as rapidly as possible to 143 degrees 

 F. 



The length of time at which cream should be held at 115 

 degrees depends on the amount of its acidity. The reason cream 

 should be held at 115 degrees is that this holding process will 

 assist in hardening the casein, thus overcoming the sticky con- 

 dition of the casein, which causes curdhng. The casein in high 

 acid cream will harden more rapidly than the casein in cream 

 containing less acid, and therefore it is not necessary to hold 

 high acid cream as long as cream containing less acid. Cream 

 is most liable to curdle when it contains from .30 to .45% of 

 acid. 



The curdling of cream takes place when the temperature 



