Color stability of C-phycocyanin (C-PC) from two different sources, mesophilic Arthrospira platensis and thermophilic Chlorogloeopsis HTF, was investigated. For this purpose, C-PC solutions were heat treated at various temperatures (50–85°C) and pH levels (3.5, 5.0, 6.0, and 7.0). Changes in color and protein concentrations were measured between 1 and 30 min. These changes were successfully modeled using a nonlinear reaction rate approach. The model parameters obtained enable a prediction of color changes for various treatment conditions and an optimization of treatment conditions with respect to color retention. Solutions from Chlorogloeopsis HTF showed a better stability at higher pH values compared to those from A. platensis, but these differences disappeared at lower pH values.
