GIFT 



Issued October 16, 1911. 



United States Department of Agriculture, 



BUREAU OF CHEMISTRY Circular No. 78. 

 H. W. WILEY, Chief of Bureau. 



CHANGES TAKING PLACE DURING THE SPOILAGE OF TOMATOES, 

 WITH METHODS FOR DETECTING SPOILAGE IN TOMATO PROD- 

 UCTS. 



By RAYMOND F. BACON and P. B. DUNBAR, 



Assistant Chemists, Division of Foods. T *. < 



INTRODUCTION. 



Tomatoes contain, on the' average, about 6.4 per cent total solids, 

 of which 3.5 per cent is invert sugar, 0.5 per cent citric acid, 0.6 per 

 cent ash, 0.9 per cent protein (Nx6.25), 0.85 per cent crude fiber, 

 and about 0.05 per cent fat. When tomatoes spoil as a result of 

 the life processes of bacteria, yeasts, and molds the sugars are rapidly 

 used up, being changed principally into acetic acid, lactic acid, 

 alcohol, and carbon dioxid, the amounts of these substances depend- 

 ing on the types of organisms which are most active in the particular 

 sample in question. During most classes of spoilage the citric 

 is also rapidly decomposed, so that its amount serves as a valuable 

 index in detecting decomposition. It is very easy to detect spoilage 

 in tomato pulp or canned tomatoes, as such products, when perfectly 

 sound, contain no volatile acids and a considerable percentage of 

 citric acid and invert sugar, and when spoiled quite large amounts of 

 volatile acids are present with little or no invert sugar or citric acid. 

 But in such complex products as tomato ketchups and the various 

 tomato sauces, of which sugar and acetic acid may be legitimate 

 ingredients, and whose composition may vary within very wide limits 

 according to the caprice of each manufacturer, it is evident that the 

 ordinary analytical determinations give very little information as to 

 the soundness of the tomatoes from which these products have been 

 prepared. It has been found, however, that the condition of the 

 tomatoes which enter into ketchups or other tomato products may 

 be ascertained by determining the nature and quantity of the acids 

 present and to a certain extent by the changes in the nitrogenous 

 constituents. Also certain analytical ratios seem to give some in- 

 formation on this point, as will be developed more in detail in con- 

 nection with the experimental data. A good ketchup or other tomato 

 product is characterized by high citric acid content and no, or very 



3955-!! 



