LIGHT SENSITIVITY OF COLORANTS USED IN ALCOHOLIC BEVERAGES

Quantum yields for photobleaching in ethanol solutions of Hexacol Red 2G Supra (E 128), Hexacol Sunset Yellow FCF Supra (E 110), caramel colour (E 150) and Liquid Red Colour (E 128) based on carminic acid, have been determined at 25 degrees C in continuous photolysis experiments using monochromatic light at each of three wavelengths 334 nm, 366 nm and 436 nm, in order to obtain an objektive measure of the sensitivity to ultraviolet and visible light of colourants used in alcoholic beverages. For photobleaching of carminic acid from Liquid Red Colour in fruit wine [pH 3.1, with 15% (v/v) ethanol] quantum yield was determined as 2.1.10(-2) mol.einstein(-1) for 334nm irradiation, 1.3.10(-3) mol.einstein(-1) for 366 nm irradiation and 5.6.10(-5) mol einstein(-1) for 436 nm irradiation, respectively. For Hexacol Sunset Yellow FCF Supra in fruit wine, the quantum yield for 334 nm irradiation was determined as 5.9.10(-4) mol.einstein(-1) and for 366 nm irradiation as 2.4.10(-4) mol.einstein(-1). Hexacol Red 2G Supra in fruit wine had a quantum yield of 3.7.10(-5) mol.einstein(-1) for 366 nm irradiation. For Hexacol Red 2G Supra and Hexacol Sunset Yellow FCF Supra for 436 nm irradiation and for Hexacol Red 2G Supra for 334 nm irradiation the quantum yields were less than 10(-6) mol einstein(-1) The following order was determined for light sensitivity in fruit wine (366 nm light): Liquid Red Colour > Hexacol Sunset Yellow FCF Supra > Hexacol Red 2G Supra. The caramel colour in aquavit [pH 7.1, with 42% (v/v) ethanol] was moderately sensitive to light with a quantum yield almost independent of irradiation wavelength. Relative quantum yields were determined as 1.6 for 334 nm irradiation, 1.0 for 366 nm and 1.0 for 436 nm irradiation. The latter value corresponded to 2.6 g caramel per einstein absorbed.