THE KINETICS OF THE LOSS, OF ALL-TRANS RETINOL AT-LOW AND INTERMEDIATE WATER ACTIVITY IN AIR IN THE DARK

All-trans retinol was suspended on a support of microcrystalline cellu lose and stored in air in the dark after equilibration at water activi ties from 0.11 to 0.75. The loss of all-trans retinol was monitored by normal phase HPLC. The rate of loss could be satisfactorily described by first-order kinetics with respect to all-trans retinol (up to more than 50% loss). The rate increased with increasing water activity in the range 0.11-0.75 a(w). Arrhenius activation energies were found to be in the range of 28-48 x 10(3) J mol(-1). A correlation between enth alpy change and Gibbs free energy change indicated a chemical compensa tion effect in the range 0.11-0.66 water activity.