Encapsulation of musk willow (Salix aegyptiaca L.) essential oil with sodium alginate and whey protein: Characterization, controlled release and mathematical modeling

The musk willow essential oil is volatile and encapsulation can protect them from environmental factors such as, light, oxygen and temperature. In the present research, preparation of sodium alginate-whey protein microcapsule containing essential oil of musk willow was carried out by internal gelation-emulsification method with encapsulation efficiency of 87.31%. The obtained microcapsules were characterized by particle size analyzer, zeta potential analyzer and scanning electron microscope. Encapsulation efficiency, swelling ratio and in vitro release of the essential oil was also investigated in fatty and acidic food simulation conditions. At acidic and fatty food simulation conditions, the complex presented negatively charged, with potential zeta values being 42.25 and 38.11 mV, respectively. The greatest electrostatic interaction occurred near pH 3.0 where the charge approached neutrality, which represents a balance between the biopolymer charges. Microcapsules shrinking in the acidic food simulation (pH=3.0) and expanding in the fatty food simulation (pH=7.0). The release results indicated that the release of musk willow essential oil from the microcapsule in both conditions occurred with a controlled manner and exhibited a slow rate. The essential oil release was found to be best fitted by Hixson–Crowell model (R2=0.993 for the acidic food simulation condition and R2=0.995 for fatty food simulation condition) which implies that a change in diameter of the microcapsule as a function of time. Mathematical modeling of release kinetics shows that musk willow essential oil loaded microsphere release follows by classical Fickian diffusion and erosion/degradation mechanisms.