Thermal degradation kinetics of neoxanthin, violaxanthin, and antheraxanthin in virgin olive oils.

A first-order kinetic mechanism was appropriate for describing the thermal degradation of epoxy xanthophylls in virgin olive oil (VOO). Consecutive reactions that involve reorganization of 5,6-epoxide groups to 5,8-furanoxide groups and subsequent rupture of the polyene chain occurred in the degradation pathways. Thermal stability was significantly affected by changes in the chemical structure (epoxy to furanoid structure), being the greatest stability for neoxanthin. A true kinetic compensation effect was found in a series of similar reactions, that is, the degradation of 5,8-furanoxides into colorless products. An isokinetic study in different VOO matrices showed that the oily medium did not significantly affect the reaction mechanisms. Consequently, the kinetic parameters obtained as temperature functions according to the Arrhenius model can be used to develop a prediction mathematical model for 5,8-furanoxide xanthophylls in VOO over time. The potential usefulness of the parameter neoxanthin/neochrome ratio is discussed as a chemical marker of heat treatment in VOO.