ANNUAL REPORT, 1946-47 31 



of 42 surface-active agents investigated, only the quaternary ammonium salts 

 showed considerable promise of making a good sanitizing agent for dairy use. 



2. A Method for Evaluating the Sanitizing Efficiency of Quaternary Ammonium 

 Compounds. (W. S. Mueller and E. P. Larkin.) A method has been developed 

 for evaluating the sanitizing properties of quaternary ammonium compounds. 

 While the method is not new, it involves the use of some new procedures and some 

 refinements of older techniques. In brief, the method consists of the addition of a 

 standardized inoculum to a germicide, and the results are simply reported as 

 percentage survival or kill for definite periods of contact time. The usefulness 

 of this method depends largely upon the efficiency of the inactivator. A hand 

 homogenizer and spectrophotometer are used in preparing the inoculum, and 

 sodium naphthuride is used as the inactivator for the quaternaries. This method 

 appears to give a truer picture of the germicidal potency under actual .working 

 conditions than is given by the phenol coefficient values as determined by the 

 Food and Drug Administration method. 



3. The Use of Quaternary Afttmonium Compounds in ^Dairy Sanitation. 

 (W. S. Mueller and D. B. Seeley.) Organisms like E. coli, S. aureus, thermophilic 

 types, and the vegetative cells of B. cereus were readily killed by quaternaries. 

 While quaternaries appeared to have no greater germicidal effect on spores of 

 B. cereus and thermodurics than older types of germicides, they were highly bac- 

 teriostatic to sporeformers. 



Approximately 0.3 percent of either cow manure or non-fat milk solids pro- 

 duced the first significant decrease in germicidal potency of a 200 p. p.m. quater- 

 nary solution. When this concentration of quaternary was used as an udder 

 wash under normal conditions, approximately 30 to 40 cows could be washed 

 before the germicidal potency of the solution decreased to a point where a fresh 

 solution was needed. No chapping or cracking of udders, teats, or milkers' hands 

 was noted when this concentration of quaternary was used. 



Metal parts of dairy equipment, when properly washed, were effectively sani- 

 tized by the use of 200 p. p.m. of quaternary. However, as much as 400 p. p.m. 

 was not effective in sanitizing the rubber inflation tubes of teat cups after each 

 cow milked when the cups were dipped rapidly in and out of tne solution. 



A quaternary spray treatment for milk cans showed a significant reduction 

 in counts. 



Dual-purpose powders such as cleaner-sanitizer combinations appear to have 

 considerable merit. 



4. The Effect of Quaternary Ammonium Compounds on Molds. (W. S. Mueller 

 and R. S. McKenzie.) Considerably less work has been done with quaternary 

 ammonium compounds in connection with molds than with bacteria. The chief 

 purpose of this study is to determine what effect quaternary ammonium salts 

 have on some molds commonly found in milk, cream, butter, sweetened condensed 

 milk, and cheese. While work on this study has not progressed far enough for 

 definite conclusions to be drawn, it is evident that not all molds are destroyed 

 after five-minute contact with a 200 p. p.m. quaternary solution at room tem- 

 perature. 



Antioxidants from Cacao. (W. S. Mueller.) Improvements have been made 

 in the extraction of certain tannin-like antioxidants from cacao, thus making it 

 possible to obtain antioxidants of greater purity. The refined products obtained 

 were found to be more effective than the earlier extracts in improving the stability 

 of butter oil, according to peroxide value, color, taste, and odor tests. The re- 

 fined antioxidants also were more effective in retarding the destruction of vitamin 



