22 EXPERIMENTS ON THE SPOILAGE OF TOMATO KETCHUP. 



the air was excluded and therefore no spoilage could occur. When 

 the cork was drawn, the organisms could grow and cause spoilage, 

 and this is a much more potent factor than the entrance of germs 

 from without. Bottling and sealing the ketchup quickly while 

 hot so completely excludes the air that only a few colonies of 

 yeast or mold may be found on subsequent microscopical exami- 

 nation. Filling at a low temperature and corking while cool 

 allows sufficient air to remain incorporated in the ketchup and 

 neck of the bottle to permit a considerable growth of the organisms 

 and a product derived from good stock may thus acquire the 

 appearance of ketchup derived from partially decayed material. 

 A ketchup in which bubbles of air are incorporated in filling may 

 show a growth of mold at each bubble throughout the mass. 

 The foregoing statements apply to ketchup containing sodium 

 benzoate as well as to the non-preservative goods of the character 

 used in these experiments. 



EXPERIMENTS WITH PRESERVATIVES. 

 SODIUM BENZOATE. 



The preservative in general use in ketchup is sodium benzoate. 

 Salicylic acid is used, but only to a limited extent. The amount of 

 sodium benzoate used, according to the labels, varies from one- 

 sixteenth to one- tenth of 1 per cent; but on some labels the amount 

 is not stated. Experiments were made to determine the amount 

 necessary to check the spoilage of ketchup. 



Two organisms, a mold and a yeast, were selected on which to make 

 the tests. The mold was the ordinary blue mold, Penicillium, which 

 was present in many of the brands of ketchup and is found commonly 

 on acid foods. It was selected on account of its prevalence and 

 resistive power. The yeast was obtained from ketchup and was also 

 a vigorous grower, forming a thick, wrinkled film on various media. 

 Any effect on the growth of the yeast could be seen readily in its 

 manner of forming the film. 



Portions of tomato gelatin to which 0.1, 0.5, 1, and 2 per cent, re- 

 spectively, of sodium benzoate were added, were first inoculated with 

 the mold. There was no development in those containing 1 and 2 

 per cent; a retarded development resulted in that containing 0.5 per 

 cent, and the growth when 0.1 per cent was used was nearly normal, 

 showing very little difference from that in the gelatin without sodium 

 benzoate. 



Ketchup was next tried as a medium, but the amount of benzoate 

 was reduced to one-sixteenth, one-twelfth, and one-tenth of 1 per cent, 

 as it was thought that some of the other constituents of the ketchup 

 were antiseptic to a slight degree. The growth in the ketchup was 



