Antioxidant and antimicrobial capacity of encapsulated thyme essential oil in alginate and soy protein-based carriers

The aim of this study was to develop a stable hydrogel carrier system for thyme essential oil (TEO) that could protect its sensitive polyphenol compounds. The impact of wall material (soy protein and alginate) on encapsulation efficiency and thymol release in simulated gastrointestinal conditions, was investigated. The release of thymol was ~ 80 % and 20 % in simulated gastric and pancreatic solutions, respectively. Thyme essential oil plays an important role as an antimicrobial and antioxidant agent. Results indicated that encapsulated TEO inside the hydrogel matrix exhibited antioxidant activity demonstrated by CUPRAC and ABTS analysis, even after thermal treatment of the beads, indicating the metal chelate effect as dominant. In vitro antimicrobial activity of encapsulated TEO has been studied against several pathogenic microorganisms such as Escherichia coli, Staphylococcus aureus, Bacillus cereus and Candida albicans. Beads coded as Ca-A1.5/SP1.5 showed anti-Candida albicans activity, while modified bead formulations Ca-A1.5/SP1.5* and Ca-A1.5/SP0.25** showed bactericidal activity against Escherichia coli and Staphylococcus aureus.