Microencapsulation of garlic extract by complex coacervation using whey protein isolate/chitosan and gum arabic/chitosan as wall materials : influence of anionic biopolymers on the physicochemical and structural properties of microparticles

The aim of this study was to encapsulate garlic extract by complex coacervation method using whey protein isolate (WPI)/ chitosan (CH) and gum Arabic (GA)/CH as wall materials. Two anionic biopolymers (GA and WPI) were used to find the most suitable wall materials to interact electrostatically with cationic CH. The complex coacervates were freeze-dried to obtain microparticles powders. The microparticles were examined for the nitrogen adsorption/desorption, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimeter (DSC), sorption isotherms, zeta potential, antioxidant activity, total phenolic content, solubility, moisture content, hygroscopicity, size distribution, and water activity. X-ray diffractograms evidenced microparticles with amorphous structure. WPI/CH and GA/CH microparticles showed surface area of 2.23 and 2.40 m2 g−1 and mean pore diameter of 5.20 and 5.37 nm, respectively. The nitrogen adsorption/desorption assay showed that microparticles presented mesopores and macropores that resulted in quick completion of microparticles surface monolayer with nitrogen. The sorption characteristics of microparticles followed the type II isotherm and Guggenheim-Anderson-de Boer (GAB) model was the best model to fit the experimental data. FTIR spectrum of microparticles reveals physical interactions between garlic compounds and functional groups of wall materials, indicating that garlic compounds were intact and encapsulated. TGA results indicated that the wall materials were effective in protecting the garlic sensitive compounds. The negative carboxyl groups (–COO− ) of GA were better than WPI for coacervation with positive amino groups (NH3 + ) of chitosan in terms of less hygroscopicity, smaller particle size, and higher retention of garlic phenolic compounds.