Thermal stability of natural pigments produced by Monascus ruber in submerged fermentation

• Heat treatment of the pigments led to significant color degradation.
• The pigments showed different behaviors to changes in temperature and pH value.
• The red color was retained at higher pH values.
• The orange pigment showed greater stability in the lower pH range.

The aim of this work was to present new data on the thermal stability of orange and red pigments produced by Monascus ruber CCT 3802 in submerged fermentation. The pigments were evaluated under different temperature and pH conditions in glass bottles with the temperature controlled using a thermostat bath. Samples of orange and red pigments were collected and submitted to measurement of the absorbance at 470 and 510 nm, respectively. The thermal degradation of the orange and red pigments followed a first-order kinetic reaction. The response surface models and empirical results described the behavior of the responses of color degradation and half-life of the pigments, and the temperature dependence of the degradation constants followed the Arrhenius model. The activation energies of the orange and red pigments were 12.65 and 11.49 kcal mol−1, respectively.