MANUFACTURE OF CASEIN. 29 



trouble need be experienced in handling that' kind of material. The 

 combination of acid in sour cream with the temperature required 

 for pasteurizing lias an injurious effect upon the normal handling 

 of the resulting buttermilk. The degree of acidity which may be 

 present in the cream at the time of pasteurization without seriously 

 interfering with the normal working of the buttermilk curd for 

 making casein has not been determined. As a large proportion of 1 be 

 casein of the best quality is used for coating paper, the numerous 

 lets of casein made were tested with special reference to their adapt- 

 ability and practical value for that industry. The tests applied in 

 the paper industry, however, give results applicable in determining 

 the value of casein for other purposes for which it may be used. The 

 requirements of casein for high-class paper-coating work are rather 

 severe, and lots not suitable for that work often can be used satisfac- 

 torily for other purposes. 



The casein is used for the purpose of fixing the coating material 

 to the paper in such manner as to make it a part of the paper. In 

 case an insufficient quantity of casein is used the coating ingredients 

 pull away from the paper when put to the test. By using more 

 casein the coating material is held firmly to the paper, which serves 

 as a practical means of determining the strength of the casein. The 

 strength or adhesiveness of all the samples made was ascertained 

 by a laboratory method used by the paper concerns, in which the 

 quantity of casein required to hold the coating mixture properly is 

 determined. 



In addition to the tests made in the laboratory large samples of 

 buttermilk casein were sent to two paper manufacturers for the pur- 

 pose of having commercial coating tests run on their large machines 

 and in that manner determine it's practical value and handling qual- 

 ities. While the results obtained in the large coating machines did 

 not always indicate the effect of the factor under observation in so 

 marked a degree as was found in the laboratory method, they did 

 demonstrate fully that a good grade of casein suitable for high-class 

 coating and lithographing work can be made from buttermilk. 



The strength test was used almost entirely in these experiments 

 as a basis for drawing conclusions as to comparative values of casein 

 in studying the effect of the factor under consideration, as there was 

 no trouble in obtaining a complete solution of the casein after adopt- 

 ing a suitable method. The time required for the casein to dissolve 

 is of importance, but slow dissolving does not necessarily indicate a 

 poor grade, as the rate of dissolving may be influenced by factors 

 that have no effect upon the strength. While the casein must dis- 

 solve within a reasonable time, its practical value is determined in 

 the final outcome largely by its strength or ability to hold the coat- 

 ing material. 



