EXPERIMENTS WITH PRESERVATIVES. 27 



of the acid will be driven off. This practice was followed in the 

 experimental work, but it has since been found that continued 

 heating in the presence of the acid has some effect upon steriliza- 

 tion, and therefore the increased amount of vinegar is effective not 

 only because of the additional acid present, but also because the 

 heating in the after process is thereby rendered more efficacious. 



This line of experiments gives promise of practical results in 

 producing a ketchup which will not only keep while in the bottle, 

 but will also keep longer after it is opened. Each manufacturer 

 must work out the quantities that could be used with his formula 

 and still retain the character of his goods. 



OIL. 



In ketchup manufacturing it is customary, if an agitator is not 

 used, to put a small amount of fat in the kettle to check the ebul- 

 lition during the reduction of the pulp. The amount used in this 

 manner is not sufficient, however, to be apparent in the ketchup. 

 Brannt a states that in some factories, where the trimmings are 

 allowed to accumulate for the season, they are given liberal doses 

 of oils and condiments when cooked, in order to disguise their defects, 

 so that the product can be placed on the market as " fresh tomato 

 catchup." That the use of oils is increasing is evident from the 

 comparison of the ketchup of the past season with that of former 

 years. 



When oil is used in ketchup, it is easily detected under the micro- 

 scope, as it appears in the form of shining, yellow globules which 

 blacken gradually when treated with osmic acid. Besides this, 

 the oil comes to the surface of the ketchup, where it can be seen 

 readily, and if considerable oil has been used a distinct layer is 

 formed. When the ketchup has been made for some time, the oil 

 changes so that the ketchup has a peculiar " greasy" odor, or the oil 

 may be so changed as to give a decidedly rancid smell to the ketchup. 

 Oil usually causes a deterioration in flavor and odor, though some 

 of the ketchups to which it has been added do not spoil readily. 

 Olive oil, cottonseed oil, and oleomargarine are used. That the oil 

 is not considered one of the regular known ingredients of the ketchup 

 is shown by the failure to declare its presence on the label. 



To test the antiseptic value of oils in ketchup, experiments were 

 made, using olive oil, cottonseed oil, and oleomargarine in the pro- 

 portions of 1 part of oil to 1,000, 750, and 500 parts of ketchup, 

 respectively. The ketchup was made in small quantities, 2 gallons 

 for each experiment. After bottling, all except the check bottles 

 were inoculated with Penicillium and kept at kitchen temperature. 

 All spoiled, and neither the quantity nor kind of oil used had any 



Brannt, W. L., A Practical Treatise on the Manufacture of Vinegar, 1900, p. 455. 



