A KINETIC-MODEL FOR EQUILIBRATION OF ISOMERIC BETA-CAROTENES

The equilibration kinetics and spontaneous isomerization of β-carotenes were studied. Carotene samples were stored at 25 or 45 °C in the dark for varied lengths of time. Isomerization reactions were monitored by HPLC with diode array detection. Two major cis isomers of β-carotene were separated and detected. Results indicated that the extent of isomerization and the proportions of cis isomers formed depended upon the solvent system in which the carotenoid was dissolved. An equilibrium mixture of β-carotenes contained 66.7 ± 3.9% all-trans-, 8.2 ± 3.1% 9-cis-, and 25.1 ± 2.9% 13-cis-β-carotene. © 1990, American Chemical Society. All rights reserved.