Pigment change of freeze-dried carotenoid powder during storage

The stability of pigment in freeze-dried carotenoid powder during dark, sto rage at 4, 25, or 45 degrees C, or under light at 25 degrees C was studied. Carrot pulp waste was used as raw material for processing carotenoid powde r by freeze-drying. The various carotenoids were analyzed by HPLC with phot odiode-array detection. Results showed that the amounts of all-trans forms of all three compounds, alpha-carotene, beta-carotene and lutein, decreased with increasing storage temperature or illumination time. The major isomer s formed during dark storage were 13-cis-alpha-carotene, 13-cis-beta-carote ne and 13-cis-lutein, while 9-cis-alpha-carotene, 9-cis-beta-carotene and 9 -cis-lutein were favored during illumination. The degradation rate of the t otal 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 beta-carotene, followed by alpha-carotene and lutein. Both the Hunter L and b values of t he powder decreased with increasing storage time and temperature, while the Hunter a value showed insignificant change (p > 0.05). (C) 2000 Elsevier S cience Ltd. All rights reserved.