KINETIC-MODEL FOR PHOTOISOMERIZATION AND CONCOMITANT PHOTODEGRADATION OF BETA-CAROTENES

The photoisomerization and concomitant photodegradation of β-carotene were studied. β-Carotene samples were stored at 28 °C in the dark or under 250 ft-c of light for varied lengths of time. Isomerization and photodegradation reactions were monitored by using HPLC with diode-array detection. Under lighted storage conditions, the photodegradation reactions predominated over the isomerization reactions. Degradation of total β-carotenes took place at a rate of 0.040 ± 0.005 day-1. The 13-cis isomer was formed in greater amounts under dark storage conditions, while under lighted storage, accumulation of the 9-cis isomer was favored. Similar trends were observed for β-carotenes in a carrot juice sample. © 1990, American Chemical Society. All rights reserved.