232 MILK 



Harding and Van Slyke, in a study of the quantity of chloro- 

 form required to restrain bacterial growth without materially 

 affecting enzym action, have observed that some of the chloroform 

 is absorbed Ijy the fat and then becomes useless as a restraining 

 agent. The greater the percentage of fat in the milk, the larger the 

 amount of chloroform lost. It settles to the bottom with the dis- 

 solved fat. Skimmed milk containing 3 per cent, protein required 

 0.2 per cent, by volume of chloroform to destroy vegetative forms 

 of bacteria gradually and 0.4 per cent, to destroy them within 

 twenty-four hours. In whole milk of 5 per cent, fat content 1 per 

 cent, chloroform destroyed the vegetative forms gradually, 1.5 per 

 cent, within twenty-four hours, and 2 per cent, in fo.ur hours. 

 Spores were not immediately destroyed even with excessive 

 amounts of chloroform. In chloroformed cheese a uniform de- 

 struction of vegetative forms was not obtained with less than 10 

 per cent, chloroform by weight. In skimmed milk digestion pro- 

 gressed at a uniform rate in the presence of 0.2 to 0.7 per cent, 

 chloroform by volume. With greater quantity of chloroform the 

 rate of digestion decreased. The decrease when 2.5 per cent, 

 chloroform was present was 12 per cent, of that occurring in the 

 presence of 0.7 per cent. Beyond 2.5 per cent, an increase to 

 30 per cent, chloroform did not retard the rate of digestion more 

 than did 2.5 per cent. The authors conclude that chloroform is 

 a fairly satisfactory agent for repressing germ life in connection 

 with the study of milk enzyms, and that quantitative studies of 

 enzym action should receive a correction of 10 per cent, where 

 2.5 per cent, chloroform or more is used. 



Babcock and Russell studied the increase of soluble protein in 

 milk obtained under aseptic precautions and after addition of 

 chloroform. As the soluble protein increased the protein pre- 

 cipitable with acetic acid decreased. The progressive proteolysis 

 is shown by the following figures : 



PROGRESSIVE PROTEOLYSIS IN MILK WITH ANTISEPTIC 



Kind and age of milk. Soluble protein. 



Average of analyses of whole milk, fresh 21 .07 per cent. 



Average analyses of whole milk, twenty-five days old 38.27 " " 



Average analyses of centrifugal skimmed milk, fresh 25 . 26 " " 



Average analyses of centrifugal skimmed milk, eight to twelve months old 73.30 " 



Maximum found in skimmed milk 91.18 " " 



Galactase was also obtained from centrifugal slime of milk 

 that had been continuously kept in contact with an antiseptic. 

 Aqueous extracts had proteolytic properties, curdled fresh milk, 

 and rapidly decomposed hydrogen peroxid. The aqueous ex- 

 tract probably contained a mixture of enzyms. 



Galactase was at first thought by Babcock and Russell to be 

 a tryptic ferment, because its action is increased in neutral or 



