DETERMINATION OF THE COLOR VALUE OF OLEORESIN CAPSICUM

15. DETERMINATION OF THE COLOR VALUE OF OLEORESIN CAPSICUM

In order to standardize the color of oleoresin capsicum it has been found that a very close match to the natural color can be attained with the proper mixture of solutions of potassium dichromate and cobalt chloride. The color standard is prepared as follows :

Into a 50 cc. Nessler tube pipette 5 cc. of a 0.1 N potassium dichromate solution¹⁷⁵ (4.904 g. K₂Cr₂O₇ per liter) and 0.5 cc. of a 0.5 N cobaltous chloride solution (5.948 g. CoCl₂.6HO₂ per 100 cc.) and make up to 50 cc. with distilled water.

The color value of the oleoresin is defined as the number of cc.'s of acetone, multiplied by 100, which are necessary to add to 1 cc. of a 1 per cent solution of the oleoresin capsicum in acetone, in order to match the color standard as outlined above. The height of the liquid in the Nessler tube should be about 8 in. and the color should be matched by looking down into the column, and not laterally.

Procedure: Weigh accurately 1.00 g. of oleoresin and make up to 100 cc. with acetone. Pipette 1 cc. of this 1 % solution into a 50 cc. volumetric flask and make up to 50 cc. with acetone.¹⁷⁶ Pour this dilute solution (0.02%) into a burette. Introduce sufficient of this solution into an empty 50 cc. Nessler tube to approximate the color of the standard (viewed through the length of the tube). Then add sufficient acetone to bring the volume up to about 45-47 cc. and make the final adjustment of color by addition of small amounts of the dilute solution (0.02%) from the burette. Finally add sufficient acetone to bring the volume to exactly 50 cc. and check the color match. Color value

Using this procedure, an accuracy of about rt 1,000 units can be obtained. The color values will vary between 5,000 and 25,000 for commercial oleoresins; a value of 14,000 is generally considered very satisfactory.

The procedure may be modified to permit the use of 100 cc. Nessler tubes and the colors of the standard, and the solution of oleoresin may be accurately matched with a Nesslerimeter.

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175 The potassium dichromate and the cobalt chloride used for these solutions should be of the grade known as "analytical reagent."

176 This procedure is satisfactory for oleoresins with a color value of 4,900 or higher; if the color value is lower, a stronger solution should be used.