Characterization of Alginate Hydrogel Beads Loaded with Thyme and Clove Essential Oils Nanoemulsions

The present study aimed to evaluate the characteristics of alginate beads filled with thyme and clove essential oils nanoemulsions (EONs). The droplet size of TEON and CEON were 201.57 ± 4.20 nm and 114.57 ± 6.40 nm and their average zeta potential were − 39.43 ± 1.10 and − 29.86 ± 6.79 mV, respectively, that is proving their high physical stability. The alginate beads were prepared using ionic gelation method at two different concentrations of sodium alginate (2.5 and 1.25% w/v) and calcium chloride (0.30 and 0.15 M). The FT-IR results revealed the new bands in the spectra of filled hydrogel beads which proved the encapsulation of EOs in the beads. The surface morphology of the beads was evaluated using scanning electron microscopy. SEM results indicated that the alginate concentration can affect the surface morphology of the alginate beads more than CaCl2. The alginate hydrogels filled with EONs showed strong antibacterial activity against Escherichia coli and Bacillus cereus. The DPPH free radical scavenging activity of filled hydrogels was dependent on the concentration of sodium alginate and calcium ion. Decreasing the alginate and CaCl2 concentrations increased the EON release. The texture profile analysis showed that the alginate and CaCl2 concentrations directly affect the mechanical properties of hydrogel beads. In conclusion, the incorporation of the EONs into the alginate beads may have an important implication in providing long-lasting antimicrobial action in various foods systems.