Degradation of b-carotene in an aqueous medium exposed to fluorescent and halogen lights under different oxygen partial pressures

During distribution and at retail level, transparent packages are exposed to natural and artificial light which may impair food quality and marketability, due to the photosensitivity of the product. The aim of this work was to study the influence of different light sources and various oxygen partial pressures on the degradation rate of b-carotene in aqueous medium. Firstly, a survey of the light sources used in commercial display areas was performed in order to investigate the most common conditions of illumination. As a function of the obtained results, three types of light (a cool white, a warm white and a halogen lamp) were chosen for the experimental phase. An aqueous solution of b-carotene was closed in clear glass vials and stored under various conditions of lighting and oxygen partial pressure. The pigment photodegradation was monitored in terms of b-carotene concentration and colour evolution. The pigment degradation was correlated to illuminance and UVA irradiance values of the selected lamps. In particular, the fluorescent lamps caused a degradation higher than the halogen lamp because of the emission on the blue region of the spectrum, where b-carotene absorbs. Lighting was a critical variable also in the presence of a low oxygen partial pressure (5 kPa) and even if more slowly than at 20 kPa of O2, the b-carotene degradated completely during storage.