CONDENSED AND POWDERED MILK 475 



Powdered milk has many advantages over liquid milk. First 

 of all there are the keeping qualities. Whereas liquid milk at 

 the best will keep only a few days, dry milk will keep many 

 months. In fact, some grades of it properly protected from 

 moisture, etc., will keep indefinitely. No bacterial action so 

 far as we have been able to determine takes place in the dry 

 product. There is rather a tendency for such bacteria as are 

 present to slowly die off. The question of bacteria is entirely 

 one of proper control up to the moment when the milk is dried. 

 That it is possible to exercise this control is shown by the results 

 of counts made on daily samples covering long periods of time. 

 During the past year something like 2800 dry samples were 

 counted in the Merrell-Soule laboratory. Of these 96 per cent 

 were below 25,000 per c.c, and had an average of about 2000 

 per c.c, 'figured to the liquid basis. 



One of the big factors in the present high cost of milk is that 

 of transportation. When we remember that seven-eighths of 

 milk is water, it is at once apparent that if we eliminate the 

 water we save seven-eighths of the cost of transportation. 

 The dried product may be shipped by freight, while liquid milk 

 must go by express. This means an additional saving in favor 

 of the dried article. 



The spray process of drying milk presents some very impor- 

 tant advantages over other processes. These advantages are 

 not all apparent at first. In fact, it is a question whether the 

 original inventor fully realized the importance of his discovery. 

 Chief of these is the rapidity with which evaporation takes 

 place. We have every reason to believe that each particle of 

 liquid as it is shot through the air gives off moisture so rapidly 

 that the milk solids are kept in a cool condition until perfectly 

 dry. This is in accord with the well-known physical law that 

 the evaporation of liquids uses up heat. In the ordinary con- 

 densation of milk it is well understood that if concentration 

 be carried beyond certain limits there is an injury to the milk 



