Fabrication of water-in-oil-in-gel emulsion gel based on pH-shifting soybean lipophilic protein and carboxymethyl chitosan: Gel performance, physicochemical properties and digestive characteristics

Abstract

In this study, Soybean lipophilic protein (LP) was modified by pH-shifting treatment and the modified LP was cross-linked with carboxymethyl chitosan (CMCS) to form an interpenetrating network structure to prepare water-in-oli-in-gel emulsion gels (W/O/G). The effects of the variation of phase ratio and addition of cross-linking agent (genipin) on the physicochemical properties and digestive characteristics of W/O/G were investigated. FT-IR and intermolecular force analysis showed that pH-shifting treatment exposed more hydrophobic groups in LP, and promoted the increase of intermolecular hydrophobic interaction and hydrogen bonding force. With the increase of GP addition and W1/O ratio, the swelling rate, water-holding capacity and UV stability of W/O/G gradually increased. While the porosity, encapsulation efficiency and in vitro degradation rate kept decreasing. W/O/G exhibited thixotropy in rheological tests and withstood a maximum compressive force of 1870 mN at a strain of 40%. Additionally, CMCS confered a certain pH response capability to W/O/G, which both maintained the gel network during pH changes and enabled the slow-release of the encapsulated bioactive in simulated in vitro digestion and improves bioaccessibility up to 80.63%. This study provided a theoretical basis for the cross-linking of modified LP and CMCS to form interpenetrating networks and enriched the gelation treatment of W/O/W emulsions.