Preparation and Performance Study of Swallowable Emulsion Gels: Composite Protein Stabilization Strategy and Structural Stability Analysis

This study aimed to fabricate functional food carriers for dysphagic patients to achieve co-delivery of multiple bioactive components. Coconut protein (CP) and soy lipophilic protein (LP) were compounded at concentration ratios (1:3, 1:2, 1:1, 2:1, and 3:1) via ultrasound assisted pH-shifting treatment. The obtained CP-LP composite proteins were further cross-linked with calcium ions (Ca²⁺) and transglutaminase (TG) to construct W/O/W emulsion gels. The feasibility of the fabricated emulsion gels as dual delivery vehicles for vitamin B 2 (VB 2 ) and vitamin D 3 (VD 3 ), as well as their applicability for dysphagia diet preparation were systematically investigated. The results indicated that CP-LP composite assembly effectively regulated protein conformational structure, which significantly improved the particle size characteristics, emulsifying activity and comprehensive functional properties of the proteins. And the 2:1 CP/LP composite presented the optimal overall performance, with solubility of 64.52%, zeta potential of −28.27 mV, and minimized particle size of 70.74 nm. Microstructural observation revealed that CP-LP composite emulsion gels possessed more compact and dense network structure compared with single protein emulsion gels, endowing the gels with superior physicochemical properties. Specifically, the 2:1 CP/LP emulsion gel exhibited the maximum water holding capacity (WHC=81.99%) and swelling ratio (SR=4.23%). In accordance with the International Dysphagia Diet Standardisation Initiative (IDDSI) framework, the composite emulsion gel was categorized as Level 5, confirming its excellent edibility and safety for dysphagic individuals. Moreover, the optimized CP-LP emulsion gel achieved high encapsulation efficiencies of 98.33% for VB 2 and 94.01% for VD 3 , along with desirable in vitro sustained-release behavior for both vitamins. This dual-carrier system enables stable encapsulation and controlled release of two bioactive ingredients simultaneously, showing distinct advantages in co-delivery functionality. Overall, this study provides a feasible and effective approach for developing nutrition-fortified functional foods for dysphagia management, holding great potential for broad applications in special dietary food industries.