SPECIFIC GRAVITY OF WHEY 207 



Leseoeur warms the milk to 45 C. (113 F.) and adds rennet; 

 after about one-half hour the whey is pressed out and filtered, then 

 it is cooled to exactly 15 C.; the specific gravity may then vary 

 between 1.029 and 1.031, but if water has been added it decreases 

 significantly, as shown below: 



Whey of pure milk =1.0300 



Whey of milk + 10 per cent, water = 1.0275 



Whey of milk -f- 20 per cent, water = 1.0251 



Whey of milk -J- 30 per cent, water = 1.0230 



Reich recommends that 20 c.c. glacial acetic acid be added to 

 500 c.c. milk, that the mixture be well shaken and heated for 

 5 to 6 minutes to 60 to 65 C. (140 to 150 F.) in a closed flask, then 

 cooled and filtered ; the filtrate is to be heated in a flask until the albu- 

 min coagulates, then filtered again and the specific gravity determined 

 after cooling to 15 C. According to his results, this varies between 

 1.027 and 1.029; a specific gravity of 1.026 is always a sign of the 

 addition of water. 



If one wishes to apply the determination of specific 

 gravity of whey to milk inspection, it is necessary to 

 develop a definite method, which must be followed out 

 exactly, for, otherwise, the result is uncertain; and be- 

 fore basing a prosecution on the results of this method, 

 one must have made careful comparisons, with the same 

 method, of normal and watered milks. 



From investigations that were undertaken in Copen- 

 hagen under Jensen's direction, it appears that these 

 two methods do not give uniform results. From 35 

 milk samples the following results were obtained: 



Rennet method Acid method 



Specific gravity Specific gravity 



7 samples 1.0270 to 1.0274 2 samples 1.0257 to 1.0259 



7 " 1.0275 to 1.0279 10 " 1.0260 to 1.0264 



15 " 1.0280 to 1.0284 15 " 1.0265 to 1.0269 



6 " 1.0285 to 1.0290 8 " 1.0270 to 1.0276 



