Continuous preparation of zein colloidal particles by Flash NanoPrecipitation (FNP)

• We developed a novel procedure to prepare zein nanoparticles via FNP.
• The effects of FNP processing parameters on the formation of ZP were investigated.
• The formation pathway of ZP via FNP with or without NaCas.
• FNP process is practical and applicable method to produce ZP in large scale.

This study utilized a facile and continuous technique termed Flash NanoPrecipitation (FNP) to produce zein colloidal particles (ZP) without or with sodium caseinate (NaCas) as the stabilizer. The colloidal particle preparations were performed through a self-made Confined Impinge Jet (CIJ) mixer, and compared with traditional antisolvent processes. The influences of FNP processing parameters on the size of zein colloid particles, including flow rates, outlet configurations, solute concentrations and ethanol concentrations, were extensively discussed. The influences of viscous properties, buffering capacity and self-assembly of zein or NaCas on particle size and size distributions were also discussed. Particle sizes of ZP produced by the FNP technique are below 350 nm, even at high zein concentrations (2.5–7.5% w/v). Solvent systems with different ethanol concentrations yielded zein colloid particles with similar size, showing an attractive feature for industrial applications and encapsulating actives with different solubility in ethanol–water binary solvent. This study opens a promising pathway for continuously producing ZP via the FNP procedure.