ABSTRACT
Lycopene is the pigment principally responsible for the characteristic deep-red color of ripe tomato fruits and tomato products. Increasing clinical evidence supports the role of lycopene as a nutrient with important health benefits, since it appears to provide protection against a broad range of epithelial cancers. Thus, means of preserving lycopene during food processing and storage have drawn much attention. Tomatoes and related tomato products are the major source of lycopene compounds and are also considered an important source of carotenoids in the human diet. Lycopene belongs to the carotenoid family. Lycopene in fresh tomato fruits occurs essentially in the all-trans configuration. The main causes of tomato lycopene degradation during processing are isomerization and oxidation. Isomerization converts all-trans isomers to cis-isomers and results in a reduction in the biological properties of lycopene. Determination of the degree of lycopene isomerization and oxidation during processing would provide a measurement of the potential health benefits of tomato-based foods. Thermal processing generally causes some loss of lycopene in tomato-based foods. Heat induces isomerization of the all-frans to cis forms. The cis-isomers increase with temperature and processing time. Heat, light, oxygen and different food matrices have effects on lycopene isomerization and oxidation. Lycopene might isomerize to mono- or poly-cis forms with the presence of heat or oil or during dehydration. Reisomerization takes place during storage. After oxidation, the lycopene molecule splits, which causes losses of color and off-flavor. The effects of heat, oxygen, light and 18presence of oil on the stability of lycopene are important issues for the nutritional quality of tomato-based foods.
