Encapsulation of thyme and cinnamon essential oils in porous corn starch: particle size, microstructure, and antimicrobial properties

Encapsulation of essential oils into a suitable, inexpensive wall material is the best strategy for their further use in food and pharmaceutical applications. In this work, porous corn starch was produced by enzymatic hydrolysis and used as a wall material for the entrapment of thyme and cinnamon essential oils. The properties of those encapsulated microcapsules were measured using various analytical techniques. The micrographs of porous corn starch demonstrated that enzymatic hydrolysis resulted in a significant number of pores. The mean volumetric particle size (D_v50) of porous starches did not differ significantly (16.3-µm) from the native starch (16.6-µm). The encapsulated microcapsules aggregated, and the D_v50 increased significantly higher than the porous corn starch. The melting temperature and process enthalpy of porous starch increased when compared to native starch. The characteristic thermograms of essential oils did not appear in the microcapsules, confirming the formation of a strong complex. The essential oil/porous starch microcapsules showed antimicrobial activity against Listeria monocytogenes and Salmonella enterica sv. Typhimurium. The obtained results provide information on the thermal stability and antimicrobial properties of essential oil-incorporated microcapsules so that they could be formulated into active packaging applications.