Water-in-water emulsions stabilized by konjac glucomannan/tragacanth gum hydrogels for riboflavin delivery

Water-in-water (W/W) emulsions as innovative transport for hydrophilic functional ingredients inherently lack stability due to the ultralow interfacial tension and thick interfacial layer. In this work, we first proposed a simple strategy to construct stable dextran (DEX)-in-poly (ethylene glycol) (PEG) W/W emulsions by utilizing the unique phase preference of konjac glucomannan/tragacanth gum (KT) hydrogels formed based on the cooling-induced intermolecular hydrogen bonds. KT hydrogels were demonstrated to present selective partition to PEG phase and could form physically crosslinking network, thus significantly improving the rheological behavior and stability of DEX-in-PEG (D/P) emulsions with no flocculation after 31 d of storage at 25 °C. Meanwhile, the average droplet size of emulsions decreased from 15.37 to 8.48 μm with TG concentration tuning from 0.2 % to 0.8 %. When encapsulating riboflavin (RIB) in D/P emulsions stabilized by KT-4 hydrogel, the storage and lighting stability of RIB were enhanced with retention rate of 60.94 % and 21.89 %, respectively. In addition, the release of RIB in the simulate gastrointestinal environment substantially reduced and the antioxidant activity of RIB was maximumly protected due to the unique pH-responsiveness of KT hydrogel network. This work provides a feasible strategy for designing stable W/W emulsions stabilized by natural polysaccharide hydrogels, and biocompatible carriers for hydrophilic functional ingredients.