Isolation and Identification of Colour Additives in Some Food Products

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Mohamed, El Sayda El Taher El Tayeb
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Fourteen different types of food commodities were analyzed for colouring materials added which were then identified against reference colouring substance. The food materials studied were samples of jams, powdered juices, sweets and soft drinks, randomly collected from local markets. A wool dying technique was used for isolation of synthetic food colours. The colouring materials were retained by the wool and stripped with dilute ammonia solution (1 part of strong ammonia to 50 part of water). The mixed colours were separated by paper and thin layer chromatography (TLC). In both chromatographic techniques, the separations were done using different solvents. The separation of colours on TLC-plates were better and sharper than those with paper chromatography. Furthermore, using the solvent system of trisodium citrate: ammonia solution: water (2: 5: 95, w/v/v) system gave better separation on paper than on the solvent ammonia solution: water (1: 99) where more spots were resolved. Similarly, solvent n-butanol: absolute ethanol: 2 N ammonium hydroxide system (60: 20: 20) was better resolving on TLC than on iso amyl alcohol: glacial acetic acid: water system (40: 20: 20). All samples of food material studied contained only synthetic colours except the soft drink (maaza) which was found to contain natural yellow colouring material in addition to the synthetic sunset yellow colour. The Rf-values measured for the reference food colours were found to be similar to the corresponding colouring matters in the food samples tested. The soft drinks yellow miranda, red fanta toot and red vita were found to contain food colours of carmosine, sunset yellow, amaranth and tartrazine, and certain unidentified onces. A side of the soft drinks, all other food samples gave single spot colour component.
May 2005
Food Products