Determinatioii of oil soluble natural dyes in foods by high performance liquid chromatography (Analytical method for natural dyes in foods III)

Abstract

A rapid and sensitive method for the determination of oil soluble natural dyes in foods was developed by using high performance liquid chromatography (HPLG) equipped with ODS column (Zorbax ODS), neutral silica gel column (Lichrosorb Si 60) and a UV detector. Analytical procedure is as follows. Food sample (5 g) was homogenized in a mixture of 25 ml of ethanol-water (1:1) and 2 ml of sesame oil, and the dyes were extracted with equal volume of ether. Samples rich in protein were subdivided and incubated for 1 h at 37 �C with 25 ml of 0.2 % protease (Pronase E) solution and 2 ml of sesame oil before the homogenization. Samples of oils and fats were mixed with 50 ml of hexane and extracted with 50 ml of ether-ethanol (3 : 1). After the addition of equal volume of hexane to the extracted solution, the mixture was shaken with 5 ml of 0.5 M ammonia solution and the aqueous phase was transferred into another separately funnel. (I ; Gurcumin, Norbixin, Bixin) To the aqueous phase, 5 ml of 1 M acetic acid was added, and dyes were extracted with ether. (II ; β-Garotene) The organic phase was evaporated to dryness on a rotary evaporater and the residue was re-dissolved in hexane. (Ill ; Paprica extracts) A part of hexane solution from procedure (II) was applied onto an activated alumina column. After washing the column with 100 ml of hexane and 30 ml of hexane-acetone (30:1), dyes were eluted with 20 ml of acetone. The dyes obtained by the procedure (I) to (III) were separately determined by HPLG. The recoveries of dyes were not less than 70 %, and this method was successfully applied to the analysis of the commercial foods. © 1984, The Japan Society for Analytical Chemistry. All rights reserved.