Kinetic Stability of Lutein in Freeze-Dried Sweet Corn Powder Stored under Different Conditions

The powder of freeze-dried sweet corn was stored under different conditions at 4, 20 and 37 degrees C for 12 weeks, and the stability of lutein and its isomers during storage were studied. It was found that total lutein content declined depending on storage conditions and the kind of lutein isomer. The highest residual of all-trans-lutein was found stored at 4 degrees C with vacuum and dark. Under the storage of air and light at 37 degrees C, major isomers 9-cis-lutein, 9'-cis-lutein, 13'-cis-lutein and 13-cis-lutein showed significant increases by 35.0, 50.0, 38.4 and 37.1%, respectively, of its original content after 12 weeks of storage, which indicated isomerization might take place during storage. The kinetics of all-trans-lutein degradation under different conditions followed first order kinetics well, the apparent rate constant values were lowest under vacuum and dark and highest under air and light at each storage temperature, confirming potential detrimental effects of oxygen and light on lutein loss.