A first-order kinetic mechanism is appropriate for describing the thermal degradation of lutein, β-carotene (β-c) and β-cryptoxanthin (β-cry) in virgin olive oils (VOO). Competitive and parallel reactions occur with lutein that yield reactions of isomerization and subsequent degradation to colorless products β-c and β-cry thermal degradation reaction was only studied as a total degradation reaction to products. The thermal stability varies among carotenoids and was greater for lutein than β-c and β-cry but being affected significantly by changes in their geometric configuration. A true kinetic compensation effect exists in lutein, β-c and β-cry degradation reactions. The isokinetic study compared kinetic and thermodynamic parameters (TP) determined in the three VOO matrices of different pigment content (high, medium, and low), and found that the oily medium did not significantly affect the reaction mechanisms. Consequently, TP can be extrapolated to any type of VOO matrix yielding a mathematical model that predicts the carotenoid degradation and (Z)-lutein isomer formation in VOO with time, and depending on temperature. © 2011 Elsevier Inc.

This work was supported by the Comisión Interministerial de Ciencia y Tecnología (CICYT-EU, Spanish and European Government) and FEDER (CE) in the Project AGL-2007-66139-C02-01 and by the Junta de Andalucía (AGR 148-2008-9).

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