Characterization of physicochemical properties of mung bean protein isolate and κ-carrageenan hydrogel as a delivery system for propolis extract.

A wide range of protein and polysaccharide structures have been applied for the encapsulation of bioactive compounds. In this research, a hydrogel was prepared using mung bean protein isolate and κ-carrageenan as a copolymer. The obtained hydrogel was used for encapsulating propolis at 1 % and 3 % (w/v). The rheological properties and the elasticity of the hydrogel samples with different percentages of propolis was investigated to determine resilience of the hydrogel. The textural analysis illustrated that propolis encapsulation does not change the hydrogel's chewiness, adhesiveness, and hardness. Fluorescence spectroscopy, FTIR, and SDS-PAGE techniques were used to determine the interactions between κ-carrageenan and mung bean protein isolate. The results suggested that electrostatic interactions and covalent bindings are responsible for gel preparation. Hydrophobic interactions contributed to propolis encapsulation. The quenching of aromatic amino acid residue and the clear propolis peak observed in fluorescence spectroscopy represented the role of hydrophobic interactions in encapsulation and gel formation. The water holding capacity (WHC) of >99 % and syneresis of <0.03 % of κ-carrageenan and mung bean protein isolate hydrogel represented an efficient structure of the hydrogel. The peak shifts of κ-carrageenan and mung bean protein isolates illustrated in the FTIR spectra were in line with SDS-PAGE results and fluorescence spectroscopy. The significantly increased encapsulation efficiency of >99 %, release rate of >50 %, and antioxidant activity of propolis encapsulated in κ-carrageenan and mung bean protein isolate suggested that the κ-carrageenan and mung bean protein isolate hydrogel is a potential delivery system and carrier for hydrophobic bioactive compounds, especially propolis.