Enhancement of Monascus Pigments Stability by Sodium Alginate and its Mechanism of Action

Monascus pigments (MPs) are natural food pigments whose stability in acidic environments is of considerable importance to the food industry. To enhance the stability of MPs, sodium alginate (SA) was utilized as a stabilizing agent and a mixture of MPs and SA was prepared (MP-SA). The stability of both the MPs and the MP-SA complex was evaluated at a pH of 3 and a temperature of 100 °C over various heating durations (0, 30, 60, and 120 min). The significant enhancement in the stability of MPs under acidic conditions is attributed to the formation of the MP-SA complex, which is evidenced by a reduction in particle size, increased electrostatic repulsion, and the establishment of hydrogen bonds, specifically C-H binding observed at a peak of 2930 cm⁻¹ and O–H binding at a peak of 3420 cm⁻¹. Furthermore, the study evaluated the storage stability of MPs over a 30-day period, both with and without the stabilizer, as well as the impact of six metal ions (K⁺, Na⁺, Ca²⁺, Mg²⁺, Cu²⁺, and Fe³⁺) on the storage stability of MPs. The findings indicate that SA effectively mitigates the degradation of MPs and protects them from the detrimental effects of metal ions. In summary, SA serves as an efficient stabilizer that enhances the stability of MPs under conditions of high acidity and temperature. This research also contributes valuable insights into the formation mechanisms and structural integrity of the MP-SA complex.

Graphical Abstract