LIME AND MILK. 265 



para-casein will find no opportunity for coagulation and escape in 

 the whey. These facts led a German investigator, some ten years 

 ago, to an announcement that he had discovered a method for 

 ■considerably inci"easing the quantity of cheese obtainable from 

 milk. 



This problem of yield is a very vital one in the cheese making 

 industry, for it is a well authenticated fact that in cheese making 

 only about two-thirds of the protein present is recovered whereas 

 one-third is lost in the whey. In general the " yield " is about lo 

 lbs. of cheese to the lOO lbs. of milk and if this could be increased 

 to II lbs., an increase of io%, as our German friend asserted ; 

 this would make a considerable difference to the pockets of cheese 

 producers. The remedy was simplicity itself, onh' to add some 

 chlorate of lime to the milk. 



Unfortunately all experiments had been made with the milk 

 of one herd, containing only o'6o% of salts. Here was a de- 

 ficiency of o'i5% and all the chlorate of calcium could do was 

 to replace the natural deficiency. When experiments were 

 repeated with milk containing the normal quota of salts, the 

 addition of chlorate of lime made no difference in yield. 



An increase of the cheese yield is possible if, previous to renneting, 

 steps are taken to decrease the proportion of the dissolved protein 

 in the milk. This can be ensured in two ways : — 



1. By preventing the development of bacteria in milk, as some 



proteid is dissolved directly or indirectly by bacterial 

 activity. This can be done by reducing the milk at 

 once after drawing to the lowest obtainable temperature. 



2. By changing dissolved proteid into either colloidal or 



suspended proteid, and this can be done by the agency 

 of heat. 



A temperature over bo degs. Cent, will solidify part of the dis- 

 solved proteid, and the higher the temperature is carried the more 

 protein will solidify. 



There is a material difference in the effect the two methods have 

 on the curdling properties of the milk. The chilling of the milk 

 has no influence on the lime salt, and such milk will coagulate in 

 a normal manner. The heating, however, has the effect of de- 

 creasing the proportion of soluble lime salts, and, if the heating 

 be carried to the boiling point and prolonged for some time, the 

 curdling properties of the milk will be probably destroyed. In 

 order to obtain a coagulum from milk which has been heated, it 

 is necessary to add some soluble milk salt, like the lactate, citrate, 

 or chlorate of calcium or citrate of magnesium. The chlorate of 

 lime shows the most vigorous action in reviving the curdling pro- 

 perties of milk. From pasteurised milk to which chlorate of lime 

 has been added, it is possible to obtain an extra yield of about 

 I lb. of cheese per loo lbs. of milk. Here, again, an intimate 

 relation between casein, lactic acid and lime is shown. 



In curdling, two-thirds of the protein is abstracted from the 

 milk and the acidity of the resulting whey is about one- third lower 

 than the acidity of the original milk. At the same time the whey 

 contains less lime salts than the milk as the curd encloses one-third 

 of the total milk salts. 



