DETERMINATION OF MADDER COLOR IN FOODS BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

An analytical method for madder color in foods by high performance liquid chromatography (HPLC) was developed. As reference/guide compounds for the analysis, ruberythric acid (1), lucidin-3-O-primeveroside (2), and alizarin (3) were selected, since they are the principle coloring constituents in the ethanol-water (1 : 1) extract of madder. Soft drink colored with madder extract was subjected to HP-20 (Diaion) ion-exchange column chromatography prior to the HPLC procedure. Recoveries of 1, 2, and 3 from the soft drink were 83, 85, and 100%, respectively. In the case of proteinaceous foods (kamaboko and lactic drink) colored with madder extract, the raw material (5 g) was homogenized in water and the homogenate was heated at 85-degrees-C for 3 hours under an acidic condition (pH 2, adjusted with HCl) to extract the reference/guide compounds. After neutralization with NH4OH solution, the homogenate was purified by HP-20 column chromatography for HPLC. By the acid treatment, 1 and 2 were partially hydrolyzed to compounds 4 and 5. On the basis of the spectroscopic data, 4 and 5 were identified as alizarin-2-O-glucoside and lucidin-3-O-glucoside, respectively. The recoveries of 1, 2, and 3 were 68, 83 and 100% (kamaboko) and 71, 78, and 100% (lactic drink), respectively, taking into account the amounts of the hydrolyzed compounds.