Degradation and isomerization of chlorophyll a and β-carotene as affected by various heating and illumination treatments

The degradation and isomerization of β-carotene and chlorophyll a as affected by oven-heating, reflux-heating, iodine-catalysed illumination, and non-iodine-catalysed illumination, were studied. Results showed that the degradations of both total β-carotene and chlorophyll a may fit the first-order model under either heating or illumination treatment. 13-cis-β-Carotene and 13,15-di-cis-β-carotene were the major cis isomers of β-carotene formed during oven heating, while 13-cis-β-carotene was favoured during reflux heating. For illumination with or without iodine as catalyst, 13,15-di-cis-β-carotene was the major cis isomer of β-carotene formed. The formation of 13,15-di-cis-β-carotene may be due to conversion of either 13-cis- or 15-cis-β-carotene. No epimerization of chlorophyll a was observed as a result of illumination.