THE ALUMNI JOURNAL. 



187 



CONDENSED HILK PREPARED BY HOT 

 AND COLD PROCESS. 



By BYRON F. MCINTYRE, l'H. G. 



The residents of our large cities are 

 familiar with the unsweetened varieties 

 of condensed milk, and to a larger extent 

 the people of the whole country are ac- 

 quainted with the sweetened or canned 

 condensed milk, and yet how little is 

 known of the detail and method of pre- 

 paration of these important food pro- 

 ducts. 



The farmer contributing his share of 

 the raw milk to a condensing factory can 

 testify to the restrictions, inspections and 

 obligations exacted by the factory man- 

 agement to secure pure milk, but the con- 

 sumer rarely discovers the untiring 

 vigilance and scientific methods put forth 

 to insure a palatable and pure condensed 

 milk. 



The art of condensing milk has been 

 perfected largely through improvements 

 in mechanical details, but the so-called 

 " vacuum principle " of removing water 

 from milk, remains unchanged, and is the 

 universal process of condensing not only 

 milk but many liquids injured by high 

 temperatures. A brief consideration of 

 this " vacuum principle " and the me- 

 chanical appliances necessary for its opera- 

 tion, may refresh our knowledge, and be 

 helpful by way of contrast with the es- 

 sential features of the preserving or cold 

 process of condensing. 



A vacuum is defined as an enclosed 

 space void of air or matter, and by vacuum 

 principle we express briefly such a com- 

 bination of pumps, condensers and tight 

 enclosures or pans, as will permit of 

 drawing from the whole apparatus the 

 larger proportion of air contained there- 

 in, so that a boiling process can be car- 

 ried on in the pans at a very low tem- 

 perature or under vacuum conditions. 

 The importance of this reduction of quan- 

 tity of air in the pan is seen when we 



consider that normally, or with the at- 

 mospheric pressure at fifteen pounds to 

 the square inch, a boiling temperature 

 would register 212 F. With but seven 

 and one-half pounds of atmospheric pres- 

 sure, or one-half of the air pumped out of 

 the apparatus, the boiling temperature 

 would register 170 F., and with nearly 

 all of the air pumped out, the boiling 

 would continue actively at ioo° F. In 

 other words, a vacuum process is perfect 

 just in proportion to the low temperature 

 obtained and held during the working of 

 same. 



It is apparent that there must be de- 

 structive changes in the milk when heat- 

 ed to 212 F. , otherwise the necessity for 

 vacuum conditions would not exist, so 

 that an inquiry as to the chemical 

 changes, must apply to temperatures be- 

 low 212 F. Authorities can be quoted 

 confirming the statement that serious 

 chemical changes are wrought in milk 

 by vacuum process temperatures, decreas- 

 ing the nutritive value of the milk, and 

 producing a series of decompositions, oc- 

 casionally noticed in burned flavors, that 

 renders the product unlike plain milk in 

 its constituent parts. 



The consumer and non -expert observer 

 will notice that the physical character- 

 istics of vacuum process condensed milk 

 are ; loss of fresh milk odor, almost com- 

 plete destruction of fresh milk taste, and 

 when mixed with water, to dilute to 

 original milk, there is no separation of 

 cream or milk lat, as in plain or fresh 

 milk. The toleration of the human 

 stomach of material digestable. and ques- 

 tionable, is well known, particularly in 

 food stuffs, both cooked and uncooked, 

 and while we have in normal milk a 

 universal food suited to all ages of the 

 human family, whether in health or sick- 

 ness, there is a growing volume of evi- 

 dence from scientific physicians and 

 chemists, unfavorable to the reputation of 



