Comparative study of oregano essential oil encapsulated in halloysite nanotubes and diatomaceous earth as antimicrobial and antioxidant composites

Multifunctional composite materials with controlled release, antimicrobial and antioxidant properties were prepared through encapsulation of oregano essential oil (OEO) into diatomaceous earth (DE) and halloysite nanotubes (Hal). DE-OEO and Hal-OEO composites were compared with their physicochemical and functional properties such as the morphology and elemental analysis, zeta-potential, chemical structure, crystallinity, thermal stability, specific surface area, encapsulation efficiency, release rate, antioxidant, and antimicrobial properties. Pristine DE showed a sunflower-like shape with an average diameter of 24 mu m, zeta-potential of -47.3 mV and BET of 0.87 m2/g. Whereas Hal exhibited a tubular structure with an average length of 788 nm and width of 115 nm, zeta-potential of -19.7 mV and BET of 68.5 m2/g. The morphology and crystallinity of DE and Hal did not change significantly after OEO loading, whereas FT-IR results confirmed that OEO was successfully loaded into DE and Hal. The thermal stability of OEO was improved after being encapsulated into Hal and DE. Both samples showed high antioxidant and antimicrobial activities. However, the DE-OEO sample exhibited stronger antioxidant and antimicrobial activities than Hal-OEO due to its higher encapsulation efficiency and release rate. Prepared materials can be used as a controlled-release, antioxidant, antimicrobial, nanofiller for food packaging, and drug delivery applications.

Automated summary

Multifunctional composite materials with controlled release, antimicrobial, and antioxidant properties were prepared by encapsulating oregano essential oil into diatomaceous earth and halloysite nanotubes. The encapsulated materials showed good morphology, crystallinity, and thermal stability, and exhibited high antioxidant and antimicrobial activities. The diatomaceous earth composite exhibited stronger antioxidant and antimicrobial activities due to its higher encapsulation efficiency and release rate.