Production and stability of water-dispersible astaxanthin oleoresin from Phaffia rhodozyma

The process of extracting the astaxanthin oleoresin from pretreated Phaffia rhodozyma cells was optimised using a Box-Behnken response surface design. Microwaving the cells at 105 W for 1 min followed by ethyl acetate extraction was the best pretreatment, and the optimal extraction conditions were 65 °C for 24 min using a solvent-solid ratio of 19:1. The order of the ability to disperse the astaxanthin oleoresin was propylene glycol> Tween 80 > Tween 20 > α-cyclodextrin, β-cyclodextrin. It was determined that the degradation of the colour of the water-dispersible oleoresin followed a first-order kinetics model. The greatest stability was observed at pH 4 and at the lowest temperature evaluated (40 °C). The thermal degradation of the pigment occurs in two steps, the first one from 0 to 1.5 h, with an E_aI = 10.31 kJ mol^-1, and the second one from 1.5 to 5 h, with an E_aII = 30.06 kJ mol^-1