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 °C or illuminated at 25 °C 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 °C, the isomerization dominated in the first 9 h; however, degradation was favoured afterwards. At 100 and 150°, 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.