Beta-carotene Isomerization

In this thesis, P-carotene was used as raw material. HPLC, LC-MS and DAD were explored and set up to identify all-trans-β-carotene, 9-cis-P-carotene and 13-cis-β-carotene. Thus the positions of cis/trans isomers of p-carotene in chromatogram were determined.Based on the experimental data, the reversible first-order kinetic model of interconversion of p-carotene in the solid phase was obtained and the kinetic parameters of cis/trans isomerization reactions were evaluated by genetic algorithm. The kinetic results showed that the rate of 13-cis isomer which isomerized to its all-trans isomer was faster than that 9-cis isomer.The area ratio changes of cis/trans isomers with time and determination of the holding time by the area ratio of by-product for 10%, 20% and 30% P-carotene dissolving in oil under heating at 120℃~170℃ were studied in this thesis. It has been observed that P-carotene was melted state in high temperature vegetable oil, the area ratios of cis/trans isomers didn't change with time under heating at 120℃~ 140℃. But after the temperature increasing to 150℃, some of by-product of 13-cis isomer was produced and the producing rate of by-product was faster with temperature increasing.The area ratio changes of cis/trans isomers and their effect on apparent absorbance for 10%, 20% and 30% p-carotene dissolving in oil under heating at 60℃~100℃ were also studied in this thesis. It has been observed that the ratio of P-carotene dissolving in oil was smaller at low temperature. Some of P-carotene was converted into crystalline or solidified state. Because of state change of P-carotene in oil, 13-cis isomer would isomerize to its all-trans isomer with temperature increasing. The area ratio of 9-cis isomer kept constant with times which illustrated that the solubility of 9-cis isomer in oil was relativly great. Tracking and detecting experiments for apparent absorbance showed that solution colour darkened and apparent absorbance increased with time at the same temperature...