Oxidation and Isomerization of Lycopene under Thermal Treatment and Light Irradiation in Food Processing

Lycopene as a natural antioxidant may provide protection against a broad range of epithelial cancers and chronic diseases. Lycopene concentrate extracted from tomatoes can be used as functional food. Lycopene would undergo degradation via isomerization and oxidation under different processing conditions, which impact its bioactivity and reduce the functionality for health benefits. Heat and light induce lycopene oxidation and isomerization of all-trans form to cis form. The effects of thermal treatment and light irradiation on the stability of lycopene were determined. Results have shown that lycopene stability depends on the extent of oxidation and isomerization. Cis-isomers are less stable than trans-isomers. The level of cis-isomers increased as treatment time increased but only for a short period during the beginning of the treatment. The major effect of thermal treatment and light irradiation was a significant decrease in the total lycopene content. A true assessment of health benefits of lycopene concentrate depends on the lycopene content and the composition of all trans-isomers and cis-isomers.