A Pickering double emulsion (DE) with an outer (O:W₂) interface stabilized by cellulose nanocrystals (DE-CNC) was designed as a co-delivery systems for chlorogenic acid (CA) and curcumin, then compared with a control DE emulsion with an O:W₂ interface stabilized with sodium caseinate (DE-NaCas). DE-CNC was more resistant to creaming during storage (6.79%, day 42) and showed higher encapsulation efficiency (EE) of CA (>90%). Conversely, both DEs exhibited similarly high EE for curcumin (>97%). The ζ-potential values were highly negative in both DEs, but tended to be lower in DE-CNC due to the highly negative charge of the CNCs. DE-CNC allowed for a steady release of CA during the oral, gastric, and intestinal phases of digestion, while a total release of CA was already observed in the gastric phase in case of DE-NaCas. The bioaccessibility of CA was similar in both DEs (~57–58%). Curcumin was mainly released in the intestinal phase with both DEs, reaching slightly lower bioaccessibility values with DE-CNC. The use of CNCs as a stabilizer for the outer interface of DEs is a promising strategy to increase the stability and EE of these systems, providing oral co-delivery vehicles capable of releasing significantly bioactive compounds during the intestinal phase of digestion.

Background/Objectives: Double emulsions (DEs) enable the simultaneous encapsulation of water-soluble and oil-soluble bioactive compounds. Their stability can be enhanced through Pickering stabilization, where solid particles are irreversibly anchored at the interfaces, forming a steric barrier. This study aimed to evaluate the release behavior of curcumin and chlorogenic acid (CA) in Pickering DEs formulated with chitin nanocrystals (ChNCs) stabilizing the outer interface (DE-ChNC) and both ChNCs and myristic acid-functionalized silica nanoparticles (SNPs-C14) stabilizing the outer and inner interfaces (DE-ChNC-C14) under in vitro gastrointestinal digestion. Methods: The optimal homogenization parameters (time and speed) for stabilizing the external interface with ChNCs were determined using a statistical design. Pickering DEs were characterized (droplet size and size distribution, microstructure, creaming, encapsulation efficiency and stability, rheological behavior) and subjected to the INFOGEST digestion method. Results: ChNCs effectively maintained the droplet size, microstructure, and ζ-potential, preventing coalescence and creaming while enhancing viscosity and gel-like behavior, contributing to improved physical stability. The CA encapsulation efficiency was higher in DE-ChNC-C14 (91.4%) than in DE-ChNC (45.0%) due to the presence of SNPs-C14 at the inner interface, which improved CA retention during storage. CA was gradually released from DE-ChNC-C14 throughout digestion, with bioaccessibility similar to that of the control DE (stabilized with conventional emulsifiers; ~60%). Curcumin bioaccessibility in the Pickering DEs was relatively high (~40%) but lower than in the control DE, as the ChNCs reduced lipid digestion and curcumin bioaccessibility. Conclusions: ChNCs and SNPs-C14 effectively stabilized the outer and inner interfaces of DEs, enabling the simultaneous release of water-soluble and oil-soluble bioactives with health benefits.

The low stability and bioaccessibility of polyphenols limit their application in functional foods. To address this, chlorogenic acid (CGA) and curcumin (CU) were selected as model compounds and co-encapsulated in spray-dried linseed oil (LO) multiple emulsions (MEs), using octenyl succinic anhydride-modified waxy maize starch as encapsulating agent. Water-in-oil-in-water MEs were prepared by two-step high-pressure homogenization and spray-dried under optimized conditions determined by response surface methodology to minimize surface oil. The resulting microparticles were characterized for encapsulation efficiency (EE), morphology, oxidative stability, and performance under simulated gastrointestinal digestion (INFOGEST protocol). Both CGA and CU exhibited high EE in microparticles (~88–90%), with spray drying significantly improving CGA retention compared to liquid emulsions. Microparticles also showed improved oxidative stability due to the presence of antioxidants. During digestion, CU bioaccessibility decreased (62.7%) relative to liquid MEs (83.6%), consistent with reduced lipid digestion. Conversely, CGA bioaccessibility was higher in microparticles (47.6%) than in MEs (29.2%), indicating a protective effect of the encapsulating agent under intestinal conditions. Overall, spray drying stabilized linseed oil-based MEs and enabled effective co-encapsulation of hydrophilic and lipophilic compounds, supporting their potential as multifunctional delivery systems for functional foods.