A novel method of preparing stable zein nanoparticle dispersions for encapsulation of peppermint oil

Zein is a group of alcohol-soluble maize proteins and is typically dissolved in 70-80% aqueous ethanol before dispersion into water to precipitate zein as nanoparticles, which can simultaneously encapsulate various lipophilic compounds co-dissolved in aqueous ethanol. However, strategies are needed to prevent the precipitation of hydrophobic zein nanoparticles at a wide pH range and the use of flammable ethanol in the industrial production. The objective of this work was to replace ethanol with nonflammable propylene glycol to prepare zein nanoparticles and stabilize nanoparticles using gum arabic (GA). Nanoparticles smaller than 200 nm were produced using a stir plate, and GA prevented their precipitation at pH 3.0-8.0. Both electrostatic and hydrophobic interactions contributed to the adsorption of GA on zein nanoparticles, with the former being more significant at a lower pH corresponding to a higher surface load. Encapsulation of peppermint oil in zein nanoparticle-GA complexes did not significantly change particle dimension and dispersion stability. The gradual release of peppermint oil from freeze-dried samples was observed at pH 2.0-8.0, reaching complete release in a shorter time at a lower pH. The established method may enable the preparation of stable zein nanoparticles for various applications in the food industry. (C) 2014 Elsevier Ltd. All rights reserved.