Stability study of blue phycocyanin from spirulina and compatibility evaluation in eye remover solution using Plackett-Burman design

Phycocyanin is a blue pigment in spirulina that has been used as a colorant in the food, cosmetic, and pharmaceutical industries. However, it has a stability problem that is affected by numerous factors, such as light, temperature, and pH. The objectives of this study were to investigate the effects of temperature (40°C, 50°C, 60°C, 70°C, and 80°C) and pH (5.0, 6.0, 7.0, and 9.0) on phycocyanin stability. The results showed that the degradation of phycocyanin followed a first-order reaction. The maximum stability of phycocyanin was at pH 6.0 (the lowest degradation rate constant, 0.0480 h^-1). An increase in temperature significantly increased the degradation rate (p < 0.05) and correlated well with an Arrhenius plot of the degradation rate (ln k) against the reciprocal of kelvin (1/T), which showed a linear regression line with an R² value of 0.9656. The compatibility study of phycocyanin with various excipients in eye remover solution, as an example of cosmetic formulation, followed the Plackett-Burman design. The results showed that 47.0% w/w glycerin had a significant destabilizing effect on phycocyanin stability. These results indicate that a pH of 6.0 and lower temperatures increase the stability of phycocyanin.