Analysis of Natural Dye in Foods. II. Determination of Cochineal Color Utilizing Methylation with Diazomethane.

Thin layer chromatography (TLC) and high performance liquid chromatography (HPLC) were used for the determination of a natural red dye from the scale insect Coccus cacti L. (cochineal) in various foods. Two kinds of orange products appeared by methylation of each of commercial cochineal color preparations and native cochineal color with ethereal diazomethane. These products were employed as reference species to decide whether cochineal color was added in foods or not. Oxalic acid was more effective than hydrochloric acid or acetic acid on the extraction of a color from foods and chromatography on an Amberlite XAD-2 column. A fraction containing a color to be tested was treated with ethereal diazomethane after removal of oxalic acid in the eluate. Orange products in the reaction mixture were detected by silica gel TLC and reversed phase HPLC. This method was found to be very suitable to determine the addition of cochineal color in foods.