EXPERIMENTS WITHOUT USE OF PRESERVATIVES. 21 



during evaporation. Of the 39 which, according to the labels, con- 

 tained sodium benzoate, 15 spoiled. The bottles of unspoiled ketchup 

 after remaining in the laboratory for about a month were placed in the 

 incubator at 95 F. for three weeks, and were then taken out, and 

 have been left in the laboratory since. The metal cap had been taken 

 off frequently for observation, and the ketchup exposed, but the 

 treatment did not cause them to spoil. 



The average number of days after which spoilage occurred for the 

 46 bottles without preservative was about fifteen, the minimum 

 number being four days, the maximum number ninety-four days. 

 The average number of days preceding spoilage in the case of 15 bot- 

 tles with preservative was twenty-four days, the minimum number 

 being three and the maximum sixty days. The majority of these had 

 0.1 per cent of sodium benzoate present; the others had a smaller 

 amount, according to the manufacturer's label. These data are 

 not at all conclusive and further work on material of known his- 

 tory will be necessary. 



STERILITY OF KETCHUP. 



To determine the sterility of ketchup, cultures were made from 77 

 of the bottles. The method used was to wipe the bottles and cork 

 stoppers with a damp towel and then remove the cork. The cork 

 puller which was used grasps the neck of the bottle in such a way as to 

 cover the opening and remove the cork without the inrush of air that 

 occurs when the ordinary corkscrew is used. A flame was then passed 

 over the mouth of the bottle, after which the upper layer of ketchup 

 was poured out, so as to discard any material which might have been 

 contaminated in handling. Tomato gelatin was used as a medium and 

 cultures were made in petri dishes. 



There were 17 plates on which no organisms developed, indicating 

 that the ketchup was sterile. Of the 60 plates having organisms, 54 

 had molds, 22 of these having molds alone; 21 plates had yeast-like 

 organisms, 3 plates having these only; 29 plates had bacteria, 4 having 

 bacteria alone. Sometimes a plate would have only one form of 

 organism, but more often there was a mixture present. Of 15 plates 

 having only one form of organism, 3 had yeast alone, 2 bacteria alone, 

 and 10 had mold alone. Of the 77 bottles of ketchup from which the 

 inoculations were made, 41 were without and 36 with preservative, and 

 of the 17 sterile ketchups, 8 contained sodium benzoate and 9 were 

 without preservative. 



A considerable part of the experimental ketchup proved not 

 to be sterile. The organisms present were of the class which 

 require oxygen for their growth and therefore they had only been 

 arrested in their activity. No growth could take place so long as 



