116 



S. A. KOSER AND W. W. SKINNER 



usually citric, tartaric, phosphoric, or lactic — are added to 

 some types of beverages and that these acids may affect the 

 longe\'ity of the organisms in question. A comparison of the 

 viabiUty of Bad. coli in a non-acid and in an acid-containing 

 beverage is shown in table 3. It will be noted that the hydro- 

 gen-ion concentration of the latter is considerably greater than 

 that of the former. The colon bacillus is killed much more speed- 

 ily in the acid-containing beverage, the effect being especially 

 marked at the higher temperature. Apparently the rapid de- 



TABLE 2 



Viability of Bad. coli in carbonated tap water under pressure and with pressure 



released 



Held at room 

 temperature 



(22-24°C.) 



Held at 1°C. 



TIME 

 INTERVAL 



At once 



24 hours 



3 days 



7 days 



18 days 



At once 



24 hours 



3 days 



7 days 



18 days 



pbessube 28 pounds peb 



square inch 



(1.9 atmospheres) at 24°C. 



440, 000 



1,500 



13 



10 cc. + 



5 cc. 



10 cc. 



500,000 



34, 000 



3,600 



100 



1 cc. + 



360, 000 



1,360 



18 



10 cc. 



10 cc. 



390, 000 



14, 700 



900 



88 



1 cc. + 



EXCESS CO2 ALLOWED TO 



ESC.U'E AT THE 



RESPECTIVE TE.MPERATURE8 



BEFORE INOCULATION 



500,000 



130 



36 



10 cc. 



5 cc. 



10 cc. 



5 cc. 



540,000 



10,300 



71 



1 cc. + 



1 cc. + 



struction of Bad. coli in the acid-containing lemon soda is due 

 mainly to the dissociation of the citric acid present, for in addi- 

 tional experiments in which this acid was omitted the death 

 rate was found to be comparable to that of the non-acid vanilla 

 soda. Also in this case the hydrogen-ion concentration had 

 decreased from pH 3.0 to pH 4.0-4.4 by the omission of the 

 citric acid. 



Experiments with other acid-containing beverages have dem- 

 onstrated that as the amount of acid is increased above that 

 indicated in table 3, the more readily is the colon bacillus killed. 



