Light-induced oxidative changes in a model dairy spread. Wavelength dependence of quantum yields.
Light-induced formation of lipid peroxides in a water-in-oil emulsion based on purified rape-seed oil (80%) was found to increase with decreasing wavelength and to have the (apparent) quantum yields (1.1 +/- 0.1) x 10(-)(3) for 436 nm, (2.6 +/- 0.1) x 10(-)(3) for 405 nm, and (4.5 +/- 0.4) x 10(-)(3) for 366 nm irradiation, as determined after 12 h of exposure to monochromatic light of an approximate intensity of 10(18) quanta.min(-)(1).mL(-)(1) and related to total light absorption. Riboflavin (0.8 ppm) had no effect on lipid peroxidation, but photodegraded with a quantum yield ((1.5 +/- 0.3) x 10(-)(5) for 436 nm, (1.7 +/- 0.2) x 10(-)(5) for 405 nm and (1.39 +/- 0.09) x 10(-)(5) for 366 nm irradiation) independent of irradiation wavelength. beta-Carotene was only photodegraded to a minor extent, but protected riboflavin against photodegradation and the lipids against peroxidation for 436 and 405 nm irradiation (reduction in quantum yield three times for 4.5 ppm beta-carotene for lipid oxidation and more for riboflavin degradation), but not for 366 nm irradiation, where beta-carotene has an absorption minimum.
Hansen
E
E
Food Chemistry, Department of Dairy and Food Science, Royal Veterinary and Agricultural University, Frederiksberg C, Denmark.
Skibsted
L H
LH
D003611:Dairy Products; D005229:Fatty Acids, Monounsaturated; D008027:Light; D015227:Lipid Peroxidation; D010938:Plant Oils / Q000737:chemistry; D000074262:Rapeseed Oil; D012256:Riboflavin / Q000737:chemistry; D019207:beta Carotene / Q000737:chemistry
D005229:Fatty Acids, Monounsaturated; D010938:Plant Oils; D000074262:Rapeseed Oil; D019207:beta Carotene; D012256:Riboflavin