Rates of thermal degradation and isomerization of all-trans-β-carotenes in air and in triacylglycerols were determined. Degradation of carotenes in triacylglycerols was faster than that in air. The 13-cis-β-carotene level in triacylglycerols was higher than in air. Oxidized materials of triacylglycerols probably facilitated isomerization of carotenes and, thus, degradation. Amounts of all-trans-β-carotenes and all-trans-α-carotenes in pumpkin decreased with an increase in heating time. The proportion of 13-cis-β-carotene increased after heat treatment started, probably due to thermal isomerization of all-trans-β-carotenes to cis-isomers, and to decreases in amounts of all-trans-β-carotenes and all-trans-α-carotenes in pumpkin. Effects of heating methods on proportions of isomers; however, were not different.
Keywords: isomerization; pumpkin; thermal degradation; triacylglycerol; β-carotene.