24 



The American Public Health Association 



(d) Application of Tests to Demon- 

 strate Efficiency. Up to this point, 

 consideration of the methods and sig- 

 nificance of the results of biological 

 tests has been given on a more or less 

 theoretical basis. It would be well to 

 point out some of the most disturbing 

 factors in the application of the tests 

 discussed. 



Tests for Sterility of Apparatus. 

 From what has already been stated the 

 conclusion must be self evident that 

 the results of any study for the de- 

 termination of the real pasteurization 

 efficiency will be of little or no value 

 if corroborated evidence is not avail- 

 able demonstrating the substantial 

 sterility of the entire apparatus of the 

 pasteurization system including the 

 cooler, before the run starts. In fact, 

 the first and most important element 

 in such a study consists in the deter- 

 mination of the existence of such a 

 sterile condition. When this is not 

 possible, and it is true that many forms 

 of commercial apparatus are substan- 

 tially , impossible to sterilize, it be- 

 comes necessary to collect a series of 

 samples of waters of condensation or 

 of previously sterilized salt solutions 

 used as wash waters and to determine 

 through the testing of them, the real 

 bacterial condition of each and every 

 important section of the apparatus be- 

 fore the treatment of the milk begins. 

 This involves a .considerable amount 

 of labor and on many occasions even 

 with such results available for consid- 

 eration along with those of the tests 

 on the samples of the raw and fully or 

 partially treated milks, it is not pos- 

 sible to come to any definite conclu- 

 sions as to the real efficiency of the 

 heating processes studied. 



One of the compensations arising 

 out of this substantial difficulty comes 

 from the fact that every study of the 

 heating efficiency of a system must of 

 necessity, determine the efficiency of 

 the cleaning operations applied to 



each section of the apparatus at the 

 close of the day's run. 



While uncleanliness of apparatus is 

 largely a piatter of old milk, either 

 dried on or moist and in a variable 

 condition of bacterial incubation and 

 while these conditions may not lead to 

 any very direct health menace to the 

 adult consumer of the product even 

 when these conditions exist in the ap- 

 paratus handling the already heated 

 and held milk, still they are most ob- 

 jectionable from other standpoints. 

 They tend greatly to reduce the gen- 

 eral quality of the milk in that they 

 promote rapid souring or other spoil- 

 age, and they tend to the develop- 

 ment of objectionable flavors and 

 tastes in the product. In the determi- 

 nation of the condition of sterility or 

 cleanliness of pasteurization apparatus 

 or of any milk handling utensils, the 

 following procedures 'are offered as 

 having given excellent results. 



Samples of any water of condensation 

 resulting from the steaming of the 

 apparatus should be collected and test- 

 ed both for total bacterial count and for 

 the quantative presence of B. coli using 

 inoculations of 1 c.c. and of smaller 

 amounts when the washing and steam- 

 ing processes have been obviously de- 

 ficient. Such waters of condensation 

 are obviously to be looked for at the 

 lower or dependent portions of the ap- 

 paratus. The points of collection should 

 be selected also with the idea of ob- 

 taining information as to the condition 

 of each important unit of apparatus in 

 the system, i. e., weigh and receiving 

 tanks, heaters, holders, cooler, fillers, 

 etc. To collect the same it is often only 

 necessary to unloosen the couplings in 

 the sanitary piping at the lowest points. 

 But in many cases the inspector must 

 use considerable ingenuity in order to 

 obtain sufficient amounts of such 

 waters without contaminating them. 

 Where there is no water of condensa- 

 tion the use of 200 c. c. of sterilized 85 



