Stability of Lutein and Its Esters

Stabilities of lutein and its esters against light, heat, acid, alkali, metal ions, oxidant and reductant were studied. Results showed that both lutein and lutein esters were unstable against light, and stable in darkness. Their preservation rate was 0.35% toward outdoor sunlight for 0.5 h while they were preserved constantly in darkness. They were slightly stable against heat but their degradation could be accelerated with decreased preservation rate under long time and high temperature. Lutein ester was more stable toward light and heat than lutein under the same condition and esterification of —OH group with fatty acids might stabilize lutein against heat and light. They were unstable with decreased preservation rate toward Fe3+,Fe2+, Cu2+ and strong acid while stable against Zn2+, Mg2+,Ca2+,K+,Na+, alkali and Na2SO3 as well as slightly stable toward H2O2. It was noted that VC could degrade significantly lutein esters and lutein, in which absorbance of lutein esters decreased more quickly than that of lutein.