Evaporated Milk — Heating 105 



casein to curdle, tends toward the formation of a hard, unshak- 

 able coagulum during sterilization, and makes the manufacture 

 of a marketable product difficult. Abnormal milk of this type 

 may come from cows approaching parturition, or too soon after 

 calving, or milk from cows suffering from disease, generalized 

 or local, or from cows in poor and abnormal physical condition, 

 which may be brought about by poor care, over-feeding, feeding 

 the wrong kinds of feed, or feed in poor condition, exposure to 

 abnormally hot weather and flies, or any other condition which 

 disturbs the physiological functions of the animal and thereby 

 affects the physical, chemical, and physiological properties of 

 the milk ; or it may be due to improper care of the milk, causing 

 it to be excessively contaminarted with germ life, or to be re- 

 latively high in acid. All such milk renders the quality of the 

 finished product uncertain and may result in heavy loss. 



In view of these facts it is obvious that the greatest care 

 should be exercised on the receiving platform, inspecting every 

 can of milk, using the most reliable means, as recommended in 

 Chapter III on "Control of Quality," p. 43, to detect suspicious 

 milk, and rejecting all milk that fails to reach the sanitary 

 standard adopted by the factory. 



HEATING THE MILK 



The equipment for heating the milk should be such as to 

 enable the factory to heat the milk with the least possible delay, 

 so as to avoid the development of acid or tO' make possible the 

 prompt cooling of the milk upon its arrival to a temperature at 

 which bacterial development is checked. In the manufacture of 

 evaporated ^ilk, the batches of condensed milk in the vacuum 

 pan must be relatively small. This milk foams more in the pan 

 than the heavier sweetened condensed milk. This factor 

 reduces therefore, the capacity of the pan. If the milk is not 

 cooled upon arrival, but is transferred immediately to the hot 

 wells, it is advisable to use numerous small wells, rather than 

 but one or a few large ones. These small wells fill rapidly and 

 the milk can be heated without delay. This system makes it 

 possible to render the bacteria inactive and harmless practically 



