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 col our (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 beve rages. For photobleaching of carminic acid from Liquid Red Colour in f ruit wine [pH 3.1, with 15% (v/v) ethanol] quantum yield was determine d 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) f or 436 nm irradiation, respectively. For Hexacol Sunset Yellow FCF Sup ra in fruit wine, the quantum yield for 334 nm irradiation was determi ned as 5.9.10(-4) mol.einstein(-1) and for 366 nm irradiation as 2.4.1 0(-4) mol.einstein(-1). Hexacol Red 2G Supra in fruit wine had a quant um yield of 3.7.10(-5) mol.einstein(-1) for 366 nm irradiation. For He xacol Red 2G Supra and Hexacol Sunset Yellow FCF Supra for 436 nm irra diation and for Hexacol Red 2G Supra for 334 nm irradiation the quantu m yields were less than 10(-6) mol einstein(-1) The following order wa s determined for light sensitivity in fruit wine (366 nm light): Liqui d 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 mo derately 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 irradiatio n. The latter value corresponded to 2.6 g caramel per einstein absorbe d.