Effects of Emulsion Concentration on Physicochemical Properties of AOP/WPC Cold Set Emulsion-filled Hydrogels

Emulsion-filled hydrogels had the advantages of emulsions and hydrogels. In this study, Pickering emulsions were embedded into a pre-AOP and WPC hydrogel polymer solution, which were subsequently gelatinized to form cold set emulsion-filled hydrogels to explore the influence of different emulsion concentrations on the swelling degrees, hydrogel strength, water-holding capacity, rheological properties and microstructural of emulsion-filled hydrogels. The results showed that emulsion-filled hydrogels were self-supporting hydrogels with good integrity, and the hydrogel network with a high hydrogel strength was formed at the emulsion concentration of 15%. Hydrogen bonding was the main driving force for the formation of emulsion-filled hydrogels. Pickering emulsions could significantly improve the whiteness (55.29±0.52), water-holding capacity (90.03%±0.82%), hydrogel strength (72.58±6.32 g), and freeze-thaw stability (26.93%±0.47%) of emulsion-filled hydrogels, helping to form a tighter hydrogel network and ensure that emulsion droplets were stable and evenly distributed in the hydrogel. Rheological measurements showed that the emulsion acted as an active filler in the emulsion-filled hydrogels. The storage modulus (G') of the emulsion-filled hydrogels was higher than the loss modulus (G''), and the two moduli were weakly dependent on frequency. Emulsion-filled hydrogels significantly increased the free fatty acid release rate and the bioavailability of curcumin compared to Pickering emulsions and corn oil during in vitro digestion. Overall, the addition of a suitable concentration of emulsion was beneficial for improving the hydrogel characteristics of emulsion-filled hydrogels and guiding the development of encapsulated delivery systems for hydrogel food products.