Oregano essential oil encapsulated in alginate beads: Release kinetics as affected by electrostatic interaction with whey proteins and freeze-drying

Considering the antimicrobial effect of oregano essential oil, this work aimed to investigate the influence of its encapsulation in alginate beads, subjected or not to electrostatic interaction with whey proteins, wet or freeze dried, in the oil release kinetics in liquid medium simulating a meat marinating solution. Alginate beads presented loading and retention capacity between 64.19%-78.64% and 57.58%-73.26%, respectively. Freeze-drying resulted in shrunk and irregular shaped particles, with higher polydispersity in size distribution, increasing release rates. Swelling studies revealed that freeze-dried beads rapidly attained similar particle sizes of wet beads. Electrostatic interaction with proteins caused a slight reduction in porosity of freeze-dried beads and a slowdown effect on the release kinetics. The power law model showed good fittings to experimental release profiles and the model exponent values in the range of 0.29 to 0.33 indicated that oil release occurred mainly by Fickian diffusion. Practical applications This study shows the influence of coating and freeze-drying processes in the release kinetics of encapsulated oregano essential oil. The alginate beads present high amounts of oregano essential oil and, therefore, can be used as a natural antimicrobial. It is important to know the influence of these processes on alginate beads with encapsulated oregano essential oil, because these factors affect its release profile, reducing or extending its effect. Knowing the behavior of these beads in liquid medium simulating a meat marinating solution after these processes is very important in order to ensure a longer release kinetic, thus improving the effect of oregano essential oil, especially during its release, and enabling its use in food industry.