Stability of lycopene during heating and illumination in a model system

The stability of lycopene during heating and illumination was studied. Lycopene standard was heated at 50, 100 and 150 degreesC or illuminated at 25 degreesC for varied lengths of time. Lycopene and its cis isomers were analysed by HPLC with photodiode array detection. The degradation of total amount of lycopene (all-trans plus cis forms) during heating or illumination was found to fit a first-order model. At 50 degreesC, the isomerization dominated in the first 9 h; however, degradation was favoured afterwards. At 100 and 150degrees, the degradation proceeded faster than the isomerization while, during illumination, the isomerization was the main reaction. The degradation rate constant (min(-1)) of lycopene rose with increasing temperature, and the activation energy was calculated to be 61.0 kJ/mol. (C) 2002 Elsevier Science Ltd. All rights reserved.