Microencapsulation of Monascus red pigments by emulsification/internal gelation with freeze/spray-drying: Process optimization, morphological characteristics, and stability

Monascus red pigments (MRPs), natural food colorants from microorganisms, are widely used in the food industry but are not very stable during storage and processing. Therefore, this study aims to microencapsulate MRPs using an emulsification/internal gelation technique to improve the stability. The highest encapsulation efficiency (EE) of 70.32% ± 0.28% was achieved when the percentage of NaCl in phosphate buffered saline (PBS) was 0.88%, the mass ratio of CaCO3 to NaAlg was 3.13, and the molar ratio of calcium to acid was 4.15. Spray-dried MRPs microcapsules had a smaller average diameter (D [4,3] ≈ 3 μm) with a smooth surface and spherical shape. Moreover, the stability assays revealed that spray-dried MRPs microcapsules processed higher retention rate, especially under the treatments of heating, light and in vitro simulated gastrointestinal digestion. The spray-dried MRPs microcapsules exhibited the lowest degradation constant and longest half-life compared with free MRPs and freeze-dried MRPs microcapsules. These results demonstrated that combining emulsification/internal gelation with spray-drying is feasible for enhancing the stability of MRPs to broad its further application in the food industry.