Vegetable oil-mediated thermal isomerization of (all-E)-lycopene: Facile and efficient production of Z-isomers

Thermal isomerization of (all-E)-lycopene to the corresponding Z-isomers was investigated in edible vegetable oils; perilla, linseed, grape seed, soybean, corn, sesame, rapeseed, rice bran, safflower seed, olive, and sunflower seed oil. Purified (all-E)-lycopene from tomato oleoresin was converted to Z-isomers in the range of 44.8-58.8% content, and the remaining ratio of total amount of lycopene isomers without decomposition were ranged from 38.8 to 79.6% after heating at 100 degrees C for 1 h in the vegetable oils. Both values were exceedingly high in sesame oil: 58.8% of total Z-isomers content and 78.3% of remaining lycopene. In particular, (5Z)-lycopene, which has higher bioavailability and antioxidant capacity as well as greater storage stability among the Z-isomers, was notably increased in that oil; approximately threefold higher than the average of the other vegetable oils.