GENERAL SANITARY PRECAUTIONS. 17 



AIR FILTRATION FOR DESICCATION. 



A great deal of difficulty in handling perishable foods arises from 

 contamination by impure air. This is particularly true of factories 

 located in densely populated places where the air is usually heavily 

 laden with dust. The results obtained by exposing agar Petri plates 

 to the air before and after the passage of the ordinary city street 

 sweeper emphasize this point. 



Air may be cleansed by heating at temperatures sufficiently high 

 to kill the bacteria present, or it may be filtered through screens made 

 by using thin layers of absorbent cotton arranged in series or be passed 

 through water or over greased slabs. Less difficulty would, of course, 

 be experienced in obtaining air free from bacteria when conditions 

 for contamination were less favorable. The only way, however, to 

 insure the proper protection of foods against air contamination is by 

 using an efficient means of removing the bacteria. It is not so much 

 the mere presence of dust in our foods that is so dangerous as it is 

 bacteria associated with it. 



CLEANSING AND STERILIZING UTENSILS. 



The modern food factory should not only be properly constructed, 

 but it should also be fully equipped with the necessary facilities for 

 keeping the building, its utensils, and the product clean. Every 

 factory should install the necessary appliances to sterilize all contain- 

 ers and pieces of apparatus used during the handling and preparation 

 of foods, particularly those which come into direct contact with the 

 material during the process of manufacture. 



Sterilization may be accomplished by the use of live steam under 

 pressure or by boiling water. The momentary exposure of utensils 

 to live steam as ordinarily practiced is insufficient ; a much longer time 

 should be allowed if this method is used. The most satisfactory plan 

 is to pass live steam into a strong cabinet under 15 pounds pressure 

 for about 15 minutes, at the end of which time bacterial life would 

 ordinarily be destroyed. Such a cabinet may be constructed of metal 

 or possibly of reenforced concrete. When hot water is used for 

 cleansing purposes it should be kept boiling, and the containers should 

 receive more than a brief immersion. 



After sterilization all containers and materials should be adequately 

 protected from subsequent contamination while not in actual use. 

 The good effects of properly cleaning vessels are often^nullified by 

 exposing them to dust when they might have been kept clean by 

 simply inverting them. 



42222 Bull. 15812 3 



