Thermal degradation kinetics of all-trans and cis-carotenoids in a light-induced model system

Abstract

Thermal degradation kinetics of lutein, zeaxanthin, β-cryptoxanthin, β-carotene was studied at 25, 35, and 45°C in a model system. Qualitative and quantitative analyses of all-trans- and cis-carotenoids were conducted using HPLC-DAD-MS technologies. Kinetic and thermodynamic parameters were calculated by non-linear regression. A total of 29 geometrical isomers and four oxidation products were detected, including all-trans-, keto compounds, mono-cis- and di-cis-isomers. Degradations of all-trans-lutein, zeaxanthin, β-cryptoxanthin, and β-carotene were described by a first-order kinetic model, with the order of rate constants as k_β-carotene>k_{β-cryptoxanthin}>k_lutein>k_zeaxanthin. Activation energies of zeaxanthin, lutein, β-cryptoxanthin, and β-carotene were 65.6, 38.9, 33.9, and 8.6kJ/moL, respectively. cis-carotenoids also followed with the first-order kinetic model, but they did not show a defined sequence of degradation rate constants and activation energies at different temperatures. A possible degradation pathway of four carotenoids was identified to better understand the mechanism of carotenoid degradation.

Keywords: 13-apo-Beta-carotenone (PubChem CID: 5363697); 13-cis-Beta-carotene (PubChem CID: 10256668); 15-cis-Beta-carotene (PubChem CID: 12305639); 9-cis-Beta-carotene (PubChem CID: 9828626); Activation energy; All-trans- and cis-carotenoids; Degradation kinetics; Degradation mechanism; Degradation rate constant; HPLC-DAD-MS; Lutein (PubChem CID: 5281243); Zeaxanthin (PubChem CID: 5280899); cis-Beta-cryptoxanthin (PubChem CID: 101088204); β-Carotene (PubChem CID: 5280489); β-Cryptoxanthin (PubChem CID: 5281235).