Decoloration kinetics of chlorophylls and carotenoids in virgin olive oil by autoxidation

- Kinetic and thermodynamic parameters for decoloration in virgin olive oil were studied.
- A first order kinetics mechanism for non-oxygen thermal autoxidation was proposed.
- Chlorophyll pigment fraction was thermally more stable than carotenoid pigment fraction.
- Differences between the oily matrixes did not affect the reaction mechanisms.
- Neither isokinetic nor compensation effect existed in both fractions of pigments.

Kinetic models are capable of predicting shelf life in keeping with the different variables that can affect the degradation of the food item. In this work, virgin olive oils (VOOs) extracted from olive fruits at three ripening stages with high, medium and low pigment contents respectively, were thermodegraded to characterize the kinetic and thermodynamic parameters for the oxidation of two pigment fractions: a green fraction (chlorophylls) and a yellow fraction (carotenoids). A first-order kinetic mechanism was appropriate for describing the decoloration processes under non-oxygen thermal auto-oxidation. A marked effect of temperature has been pointed out, with the carotenoids (CARs) being the most affected by heat. The kinetic constants for the CAR degradation were about 3.6 times higher than the respective constants for chlorophylls (CHLs) that showed a more stable structure to decoloration by heat. As well, higher activation energy of CHLs (16.03 ± 0.26 kcal·mol− 1) as compared to CARs (15.45 ± 0.17 kcal·mol− 1) implies that a smaller temperature change is needed to increase the kinetic constant of CHLs.Neither isokinetic ratio nor compensation existed between the three VOO matrixes and further, for each pigment fraction (CHLs or CARs) all kinetic constants were explained by a single Arrhenius line. Consequently, the differences between the oily matrixes did not significantly affect the decoloration mechanisms, and moreover, the kinetic parameters obtained as temperature functions according to the Arrhenius model, can be used to develop a prediction mathematical model for decoloration of CHL and CAR pigment fractions in VOO over time and depending on temperature.