Effects of ozone and oxygen on the degradation of carotenoids in an aqueous model system

Abstract

The effects of ozone and oxygen on the degradation of carotenoids in an aqueous model system were studied. All-trans β-carotene, 9-cis β-carotene, β-cryptoxanthin, and lycopene were adsorbed onto a C18 solid phase and exposed to a continuous flow of water saturated with oxygen or ozone at 30 °C. Carotenoids were analyzed using HPLC with a C30 column and a photodiode array detector. Approximately 90% of all-trans β-carotene, 9-cis β-carotene, and β-cryptoxanthin were lost after exposure to ozone for 7 h. A similar loss of lycopene occurred in only 1 h. When exposed to oxygen, all carotenoids, except β-cryptoxanthin, degraded at lower rates. The degradation of all the carotenoids followed zero-order reaction kinetics with the following relative rates: lycopene > β-cryptoxanthin > all-trans β-carotene > 9-cis β-carotene. The major degradation products of β-carotene were tentatively identified on the basis of their elution on the HPLC column, UV - Vis spectra, and electrospray LC - MS. Predominant isomers of β-carotene were 13-cis, 9-cis, and a dicis isomer. Products resulting from cleavage of the molecule were β-apo-13-carotenone and β-apo-14'-carotenal, whereas epoxidation yielded β-carotene 5,8-epoxide and β-carotene 5,8-endoperoxide.