Pigment change of freeze-dried carotenoid powder during storage

The stability of pigment in freeze-dried carotenoid powder during dark storage at 4, 25, or 45°C, or under light at 25°C was studied. Carrot pulp waste was used as raw material for processing carotenoid powder by freeze-drying. The various carotenoids were analyzed by HPLC with photodiode-array detection. Results showed that the amounts of all-trans forms of all three compounds, α-carotene, β-carotene and lutein, decreased with increasing storage temperature or illumination time. The major isomers formed during dark storage were 13-cis-α-carotene, 13-cis-β-carotene and 13-cis-lutein, while 9-cis-α-carotene, 9-cis-β-carotene and 9-cis-lutein were favored during illumination. The degradation rate of the total amount of all-trans plus cis forms of each pigment fits a first order model, and the highest rate constant (day−1) was found for β-carotene, followed by α-carotene and lutein. Both the Hunter L and b values of the powder decreased with increasing storage time and temperature, while the Hunter a value showed insignificant change (p>0.05).