DAlftY FARMING DAIRYING. 5<S3 



ized or boiled milk as well as condensed milk likewise presents a similar micioscopic 

 appearance. In these cases the fat globules are homogeneously distributed through- 

 out the miscroscopic field. The fat aggregations that are so characteristic of the 

 preparations of normal milk and cream are here entirely lacking." 



This difference in the microscopic appearance of pasteurized milk 

 and cream was verified by hundreds of preparations of milk and cream 

 from different sources. 



It was found by combining the microscopical and viscometrical tests 

 that the change in consistency occurred at practically the same tem- 

 perature at which the microscopic clots in the milk broke up. This 

 change occurred between 59 and 65° C, depending upon the varying 

 condition of the milk. "This relation seems to show that the greater 

 consistency of natural cream is very intimately connected with the 

 presence of these fat aggregations. In milk this is less pronounced, 

 owing to the greater effect that the serum solids have upon the total 

 consistency of the fluid." 



The observations were extended to colostrum, and to the effect of 

 centrifugal force and of acids and alkalies on the consistency of milk 

 and cream. It was found in every case that in cream raised by a sepa- 

 rator the tendency toward grouping of the fat globules was greatly 

 reduced, "the fat globules often being as homogeneously distributed 

 as in pasteurized cream/' 



On the restoration of the consistency of pasteurized milk 

 and cream, S. M. Babcock and II. L. Russell (Wisconsin Sta. Bpt. 

 1896, pp. 81-94, Jigs. 3). — Continuing the investigations noted in the 

 preceding article, experiments were made with a view to restoring the 

 consistency of pasteurized products by some artificial means. For this 

 purpose the addition of finely divided egg albumen, tricalcium phos- 

 phate, and blood fibrin were tried with only partial success. It was 

 found that infinitesimal quantities of rennet (1 : 200,000 parts or less) 

 were sufficient to restore the consistency of cream in a few hours so 

 that cream containing only about 12 per cent of fat whipped easily in a 

 few minutes, while it was impossible to whip the same cream untreated. 

 The action of rennet, however, continued with sufficient rapidity, even 

 at refrigerator temperature, to cause the cream to thicken in the course 

 of time. 



"The development of acid with the increasing age of the milk constantly accel- 

 erated this curdling effect. The effect of acid upon rennet is to increase its rate of 

 action, and on this account the gradually increasing acidity of milk makes it impos- 

 sible to sufficiently retard it for practical purposes. Numerous experiments were 

 also made with pepsin, Avhich was found to be even more suitable than rennet, as its 

 presence could in no way be detected by taste or smell. 



"The addition of this enzym might have practically solved the problem had it 

 not been for the fact that its rate of action, like that of rennet, is continually 

 increased by the biological changes that occur in the milk even at low temperatures." 



In experiments with pancreatin, trypsin, and the vegetable ferment 

 papain, it was found that undesirable by-products were formed, render- 

 ing them unsuitable. 



