Shelf stability of lutein from marigold (Tagetes erecta L.) flowers in vegetable oils

The stability of lutein in sunflower and rice bran oils was investigated in the temperature range 25–40 °C. Experiments were made using a standardized plant extract at 5% by weight of lutein derived from the flowers of Tagetes erecta L. Samples of the pigment in oil were incubated at each temperature for up to 10 days and the time course of degradation was monitored. A kinetic analysis of the data showed that thermal degradation follows first-order kinetics, with apparent activation energies of 60.9 kJ mol −1 (in sunflower oil) and 44.9 kJ mol −1 (in rice bran oil). From the estimated kinetic parameters, the carotenoid half-life at 4 and 20 °C were determined. The results obtained indicate that lutein is more stable in sunflower oil. The observed differences in stability could be a reflection of the different fatty acid composition of the two oils and the presence of endogenous antioxidants.