Photochemical and Thermal Stability of Carmoisine, Sunset Yellow and Tartrazine Food-Coloring Dyes in Commercial Beverages

Abstract

It has been a custom in many developing countries to put beverages into display under sunlight. The photostability as well as dark degradation of the titled color dyes used in the commercial beverages Fanta^® and Mirinda^® have been therefore investigated in the presence of food acids citric and ascorbic acids. The degradation products have been identified in case of Sunset Yellow as sulfanilic acid and the 2-sulfonic acid-5-amino-6-hydroxyl naphthalene sodium salts. The degradation products of Carmoisine are naphthionic acid (1-sulfonic acid sodium salt-4-amino-naphthalene) and 1-naphthalene sulfonic acid-3-amino-4-hydroxyl naphthalene sodium salts. A third food coloring dye, Tartarzine, has also been studied for comparison. The dark reactivity of the studied dyes in the presence of citric or ascorbic acids was confirmed to obey second-order kinetic model. The stability of the dyes goes in the order Tartarzine > Sunset Yellow > Carmoisine with evaluated values of energies of activation (E_a) of 19.9, 16.5 and 14.8 kJ mol^-1, respectively. The Photochemical quantum yield (jc) for the three dyes have been determined showing that Carmoisine in the presence of ascorbic acid has the highest photostability when compared with the other two dyes.