An on-line color monitoring system for solid foods to be used during supercritical carbon dioxide (SC-CO2) pasteurization was designed and tested. The experimental apparatus described here allowed for the measurement of reflectance spectra and color parameters (L*, a*, b*) during (on-line) as well as before and after treatments (off-line). The results demonstrated that SC-CO2 pasteurization applied at 12.0 MPa, 40 degrees C slightly affected the color of freshly cut pieces of coconut and carrot during the process performed at different treatment times (10, 20, and 30 min), Reflectance spectra of coconut, acquired on-line, showed that CO2 influenced the color immediately upon treatment: lightness (L*) changed from 86.10 +/- 2.80 at 1 min to 79.57 +/- 0.74 at 30 min. The decompression was demonstrated to be the critical parameter affecting the color of carrot. The off-line measurements showed that 30 min of treatment induced 38% and 22% decrease of redness (a*) and yellowness (b*), respectively. The proposed apparatus allowed for a non-invasive, immediate and direct monitoring of food color before, during and after SC-CO2 pasteurization. (C) 2011 Elsevier Ltd. All rights reserved.