Thermal stability of natural pigments produced by Monascus purpureus in submerged fermentation.

The major aim of the current study was to assess thermal stability of red pigments produced by Monascus purpureus ATCC 16362/PTCC 5303 in submerged fermentation. Natural pigments were produced by Monascus purpureus using stirred tank bioreactor. Stability of Monascus purpureus pigments was assessed under various temperature (50.2-97.8°C), salt (0%-2.5%), and pH (4.3-7.7) values. Thermal degradation constant and half-life value of the red Monascus purpureus pigments were analyzed using response surface methodology followed by a first-order kinetic reaction. Results of this study showed that pH, temperature, and salt content could affect red color stability of Monascus purpureus. The pigment showed various stabilities in various thermal conditions (temperature, salt, and pH). At high temperatures, degradation constant of the red pigments increased with decreasing pH, revealing that the Monascus red pigment was destroyed at lower pH values and salt could affect stability of the red pigments at lower temperatures.