CONDENSED AND POWDERED MILK 465 



milk at different times of the year. In spring or early summer 

 there is a greater tendency for curdy milk than later in the sea- 

 son. Unfortunately the intervals between the samples of the 

 June experiment are too great to show exactly when the forma- 

 tion of the curd begins, but the sample containing 28.02 per 

 cent solids showed such a curdy condition that it strongly suggests 

 that that milk would have been curdy at a considerably lower 

 degree of concentration. In the August milk curdiness started 

 with 27.33 per cent solids, and in the November milk with 

 28.23 per cent solids. 



In June the fresh milk contained .16 per cent acid, in August 

 .12 per cent, and in November .17 per cent. The greater curdi- 

 ness in the June milk could, therefore, not have been due to the 

 higher acid content of that milk, but it may have been due to 

 the peculiarity of the casein in milk coming largely from fresh 

 cows, or to the feed, or to both of these factors. 



The results of these experiments agree very closely with the 

 general experience in the manufacture of evaporated milk. 

 Milk in early summer is more difficult to process, owing to its 

 tendency to become curdy, than milk processed at any other 

 time of the year. 



The experiments above described related to the conditions at 

 one factory only. Other factories may and do have other con- 

 ditions, and experiments in some of them would undoubtedly 

 yield different results. It has been experimentally shown that, 

 in some localities and at certain seasons of the year, a market- 

 able evaporated milk cannot be made when the product is 

 condensed sufficiently to contain over 24 per cent solids. 



STERILIZATION AND KEEPING QUALITY 



The temperature to which the milk is exposed during the 

 condensing process destroys many of the microorganisms pres- 

 ent in the fresh milk, but some of the more resistant forms are 



2H 



