Determination of synthetic colorants and natural carmine in wines

Abstract

Methods were developed for the determination of synthetic colorants and natural carmine (E120) in wines. The synthetic colorants studied were tartrazine (E102), quinoline yellow (E104), sunset yellow (E110), azo ruby (E122), amaranth (E123), ponceau 4R (E124), and erythrosine (E127). The colorants were extracted using solid-phase extraction (SPE) with NH₂ cartridges. The extracted colorants were then analysed by high-performance liquid chromatography (HPLC). The compounds were identified by comparing the spectrum of extract with spectra in a UV-vis spectral library of known food colorants. The detection limits in red wine ranged from 0.1 mg/l to 0.2 mg/l. Diode array detection and library search makes the method very effective in identifying forbidden colorants in wines. SPE is sufficiently effective in separating and concentrating colorants from wine. The effect of added colorants, e.g. azo ruby (E122), amaranth (E123) and tartrazine (E102) on the UV-vis spectra of red and white wines were studied. The added colorants could be identified in this way but not as accurately as by the HPLC method.