Design of vitamin-loaded emulsions in agar hydrogel matrix dispersed with plant surfactants

Polysaccharide colloids and gels supplemented with bioactive compounds are very common in the food industry, although hydrophobic substances can significantly affect the structure and physicochemical properties of hydrogels. In the present study, the impact of natural surfactants, saponins, on agar hydrogels containing vitamins A and E was evaluated. The study started with the research of droplet size distribution of vitamin-loaded aqueous emulsions, stabilized by saponins. A composition containing vitamins at a concentration of 2 mg mL−1 and Sapindus mukorossi saponins at a concentration of 0.1 mg mL−1 was used for further analysis. The second stage of our studies includes the introduction of the emulsion into a hydrogel matrix based on agar. The vitamin-containing hydrogel systems obtained were studied to verify how the vitamin, saponin, and agar concentration affect the mechanical and swelling properties of the materials, as well as their color and transparency. An important aspect was to indicate how the presence of vitamins affects the activity of water molecules measured by low-field NMR. The collected results indicated that, as a result of the use of saponins, stable emulsions that can be incorporated into hydrogels can be obtained while the size and properties of the droplets are maintained without changing their physicochemical properties.