United States Department of Agriculture, 



BUREAU OF CHEMISTRY Circular No. 25. 



H. W. WILEY, Chief of Bureau. 



COLORING MATTERS FOR FOODSTUFFS AND METHODS FOR THEIR 



DETECTION. 



[A preliminary report made to the Association of Official Agricultural Chemists.] 



By W. G. BERRY, 



Associate Referee on Colors. 



INTRODUCTION. 



This preliminary report, including a classification of the colors used 

 in food products and methods for their detection, is published in its 

 present tentative form for the purpose of crystallizing what work has 

 been accomplished in this large field and presenting it for suggestion 

 and criticism. A basis for future work of a more detailed nature is 

 thus afforded, and it is hoped that criticisms and contributions to the 

 subject will be made by those working in this field. 



W. D. BIGELOW, 



Acting Chief, Bureau of Chemistry; 

 liefer ee on Food Adulteration, A. O. A. C. 

 Approved: 



JAMES WILSON, 



Secretary of A griculture. 



WASHINGTON, D. C., August 22, 1905. 



CONTENTS. Page. 



Scope of the investigation 3 



Classification of colors 7 



I. Coal-tar color lakes 7 



II. Natural colors of vegetable and animal origin 8 



III. Organic lakes 13 



I V. Mineral pigments 13 



V. Coloring compounds 15 



Methods of analysis 15 



I. Wines 15 



A. Preliminary tests 16 



a. Examination for natural or artificial coloring matters 16 



Paris municipal laboratory test 17 



Dupre test 



b. Examination for coal-tar colors 17 



Mansfield's test 17 



Cazeneuve's test 18 



Falieres-Kitter test 18 



c. Examination for foreign vegetable colors 18 



B. Separation and identification of the coal-tar colors 20 



a. Method of Sostegni and Carpentieri 20 



6. Arata's method 20 



c. Wolff-Winterthur method 20 



d. Detection of coal-tar colors by extraction with solvents ... 20 



Paris municipal laboratory method 20 



