The influence of light of different wavelengths on chlorophyll-containing foods

Abstract

The influence of light on a model system (sunflower oil spiked with chlorophylls) depending on the wavelengths of the visible spectral range was studied. A fluorescent lamp of daylight type was used for exposure. Subranges of the light spectrum were selected using interference filters. The irridiance of each sample was measured and the number of quanta absorbed by the model system was calculated. The sensitivity to oxidation was determined by the oxygen consumption during exposure time. The resulting effects of oxidation, such as the degradation of the chlorophyll derivatives and the formation of pentane as a secondary oxidation product, were measured after exposure. The greatest quantum-dependent sensitivity was detected around 650 nm, the lowest around 500 nm. It was shown that the quanta absorbed by the absorption maximum of chlorophyll at 650 nm are most effective to photooxidation. This sample showed the greatest chlorophyll degradation and an increase in the pentane concentration. The model system exposed to the full spectrum absorbed quanta of different wavelength ranges, which contribute more or less to photooxidation. The quantum yield over the whole spectrum lies tn the range of the samples exposed to selected wavelength ranges. When selecting packaging for chlorophyll-containing foods, the two critical spectral ranges around 400 nm (yellow-green) and 650 nm (blue-green) need special consideration. Foods mainly irradiated by fluorescent light need more protection in the lower wavelength range and foods irradiated by natural daylight in the longer wavelength range. © 2001 Academic Press.