Understanding of dispersion and aggregation of suspensions of zein nanoparticles in aqueous alcohol solutions after thermal treatment

In the present study, the physicochemical properties of zein nanoparticles pretreated by different ratios of ethanol/water or isopropanol/water combing with thermal treatment (at 60 °C for 10 min) were investigated. Our results indicate that particle size increased with higher concentration of ethanol initially from 70% (13.4 nm) to 85% (29 nm). In water/isopropanol mixtures (65-95%, v/v isopropanol), the particle size proportionally increased with the concentration of isopropanol. In addition, it is demonstrated that the change of the concentration of alcoholic solution induced the exposure of internal sulfhydryl group to the surface of unfolding protein. Moreover, the nanoscale structures of zein were revealed by AFM, indicating that uniform granular zein packed compactly in a regular fashion resulting in a uniform microstructure at 90% isopropanol. Furthermore, rheological results suggest that viscosities of all samples decreased with an increasing shear rate. In summary, the findings of this study could facilitate the rational development of zein-based nanoscale delivery systems for the transportation of hydrophobic bioactive compounds with ideal surface morphology and functionalities for food and pharmaceutical applications.