Calcium-modulated double emulsion for co-delivery of Monascus pigment and calcium

Monascus pigments are susceptible to environmental and processing conditions, leading to degradation and reduced functionality, while calcium bioaccessibility remains limited due to interactions within complex food matrices that can restrict its release and uptake during digestion. In this study, a gel-in-oil-in-water (G/O/W) double emulsion with a gelled internal phase was engineered for the co-delivery of Monascus pigments and calcium, enabling systematic investigation of the role of calcium in modulating emulsion structure, stability, and digestion behavior. Physicochemical characterization, including droplet size, ζ-potential, rheology, and SEM, indicated that a gel-like internal network strengthened droplet interfaces, minimized coalescence, and enabled high encapsulation efficiency (92.94 ± 0.35%). In vitro digestion studies showed that the emulsion underwent clear structural evolution from intact droplets in the oral phase, to controlled aggregation in the gastric phase, and partial breakdown in the intestinal phase. This progressive structural change directly influenced the release kinetics of both Monascus pigments and calcium ions, resulting in enhanced bioaccessibility (64.94 ± 1.7% for pigments; 60 ± 2.7% for calcium). The formulation containing 5 mM calcium showed the most favorable stability and structural integrity. These findings demonstrate that calcium-mediated ionic interactions, together with the internal gel network, can regulate emulsion structure, stability, and simultaneous delivery performance, providing mechanistic insight into the stabilization and release of functional ingredients during digestion. The study offers a versatile platform for designing functional food and nutraceutical delivery systems based on double emulsions.