Use of zein for nanoencapsulation of eucalyptol

Zein, a hydrophobic protein from maize, is a promising agro-based polymer for encapsulating essential oils due to its hydrophobicity, amphiphilicity, and self-assembling character. This study used antisolvent precipitation technique that makes use of phase-separation of zein in aqueous ethanol solutions to encapsulate eucalyptol or eucalyptus oil into zein. Eucalyptol, a natural biopesticide, is highly volatile causing its active time to be short. Encapsulation into zein improves its stability and extends its activity. This research also investigated the optimal conditions for the encapsulation procedure by considering the major controlling factors, such as the ethanol contents of beginning and final solutions, concentration of zein, and eucalyptol to zein ratio. The optimal conditions determined for the encapsulation of eucalyptol were applied additionally to that of eucalyptus oil. Results confirmed that eucalyptol and the minor components of eucalyptus oil were successfully encapsulated by zein with average particle size of about 200 nm. The optimal encapsulation condition entails ca. 2% zein in 20% ethanol, and the encapsulating efficiency is about 80%. This research further demonstrates that encapsulation efficiency is influenced by the solubility of the target chemical ingredient, while the prolongation of release time depends on the wall thickness of the produced particles. As the demonstrated encapsulation process is applicable to any target chemical ingredients that are soluble in ethanol, the same encapsulation strategy can be used for many pesticides and pharmaceutical ingredients.