Preparation characteristics of monodispersed oil-in-water emulsions with large particles stabilized by proteins in straight-through microchannel emulsification

We investigated the preparation characteristics of monodispersed oil-in-water (O/W) emulsions with large particles stabilized by proteins using a straight-through microchannel (MC). Bovine serum albumin (BSA), β-lactoglobulin, γ-globulin, lysozyme, soybean flour, whey protein, and egg white protein were used as emulsifiers. Stable monodispersed emulsions were prepared using BSA, β-lactoglobulin, soybean flour, and whey protein, whose particle sizes ranged from 41.0 to 44.1 μm, and whose coefficients of variation were less than 6.5%. Monodispersed emulsions could not be prepared using γ-globulin, lysozyme and egg white protein as emulsifiers. The particle became significantly bigger and its monodispersity decreased with the increase of the dispersed-phase flux, but monodispersed emulsion was successfully prepared even when the dispersed-phase flux was increased to 30 L/(m2 h). Particle formation behaviors were closely related to protein solution properties, such as interfacial tension and contact angle on a silicon plate. Low interfacial tension and contact angle were shown to be beneficial to the particle formation. The electric charge of the protein was determined to be another important factor in particle formation. When protein solution pH was lower than its isoelectric point, the electronic attractive interaction worked between the negatively charged silicon MC plate and the positively charged protein molecules, resulting in unsuccessful emulsification. These monodispersed emulsions stabilized by proteins were thought to be useful as food or chemical materials.