UNSWEETENED CONDENSED MILK DEFECTS 259 



separates and the difficulty of overcoming this defect, differ 

 greatly with locality and season of year. The fat globules in 

 milk from the Channel Island breeds, average two to three times 

 as large as those in milk from the Holsteins and Ayrshires. 

 Therefore, factories located in Holstein and Ayrshire territories 

 are not troubled nearly as much with fat" separation in evap- 

 orated milk, as factories in localities where Jerseys and Guernseys 

 predominate. 



Again, the fat globules are largest at the beginning of the 

 period of lactation and decrease in size as the period of lactation 

 advances. 



In order to equalize the output of evaporated milk through- 

 out the year, condensing concerns make every effort to induce 

 their patrons to time the breeding of their cowls in such a way 

 that the fresh cows are distributed throughout the year. The 

 result of this practice is, that the milk supply of these factories 

 represents at all times a mixture of milk from cows at all stages 

 of their period of lactation. This naturally equalizes the be- 

 havior of the finished product as far as separation of the fat is 

 concerned, facilitating the control of this separation. On the 

 other hand, in localities of factories, newly established, summer 

 milk is largely produced and the majority of cows freshen in the 

 spring. This causes a marked increase of the size of the average 

 fat globules in early summer, rendering the manufacture of 

 evaporated milk, that does not separate its fat, more difficult. 



Effect of Degree of Concentration. Other conditions being 

 the same, the more concentrated the product, the less the danger 

 of fat separation in the finished product. The leason for this 

 lies in the fact that with the concentration the viscosity and the 

 resistance force of the evaporated milk increase, hindering the 

 fat globules in their upward passage. This is partly offset by 

 the increase in the specific gravity of the product, but the in- 

 crease of the resistance force exerts a stronger influence against 

 separation of the fat, than the increase of the gravity force exerts 

 in favor of fat separation. 



However, as the concentration increases, the evaporated 

 milk becomes more sensitive to the sterilizing process iajid 

 beyond certain limits it would be necessary to reduce the tem- 

 perature or the length of exposure to heat, or both, in order to 



