108 THE COAGULATION OF CONDENSED MILK, 



proceeds radially, and finally the enlarged blobs or lumps fuse 

 together into a solid jelly. This occurs when the milk is at rest. 

 When agitated from day to day, as was done in the experimental 

 work which will be mentioned later, the thickening begins at the 

 surface-margin and proceeds inwards and downwards. 



The manufacturer considered that tlie trouble was caused by a 

 fault in the condensing plant, whicli, he considered, permitted the 

 entry of water carrying salts of lime and magnesia in solution, 

 and this appeared to be a feasible explanation in view of some 

 experiments that were made by the Department of Agriculture 

 of Victoria. Briefly, these experiments consisted in adding 

 small quantities of lime salts ( = 0-02% of CaCOo) and of 

 magnesia salts, and incubating the milk thus treated. It was 

 concluded that small quantities of lime and magnesia salts bring 

 about a thickening or coagulation of condensed milk, and in this 

 ■connection it was noted that saccharated lime o-r viscogen is used 

 commercially to thicken cream. 



The action of the small quantities of calcium carbonate was so 

 unexpected, that I repeated the experiment with specimens of 

 condensed milk from the same firm. These specimens were 

 described as showing no tendency to coagulate. A control test 

 was made at the same time and treated in the same way with 

 the exception that the calcium and magnesium salts were not 

 added. Both tests were retained in the flasks in which the 

 milks had been agitated for two hours at 54^^ previous to incuba- 

 tion at 37^. The contents of the flask with the salts showed 

 signs of thickening on the fifth day, when a few nodules were 

 visible at the surface margin, and it appeared as if the salts had 

 induced the formation of the viscosity. Then the milk began to 

 thicken from the margin of the surface inwards. At this time, 

 however, it was noted that the check-test had also begun to 

 thicken. The coagulation proceeded in both tests until in about 

 a month the contents of each flask had become a jelly. The 

 only difference between the two was that the test with the salts 

 had a start of two or three days over the control. Both of 

 these milks contained the coccus which had been in the original 

 condensed milk. 



