Encapsulation of nanoparticles of d-limonene by spray drying: Role of emulsifiers and emulsifying techniques

Submicron emulsion particles of d-limonene prepared by a microfluidizer and ultrasound were spray dried to produce nanoparticle encapsulated powders. Maltodextrin combined with a surface-active biopolymer (modified starch or whey protein concentrate) or a small molecule surfactant (Tween 20) was used as the wall material. Results showed that microfluidization was an efficient emulsification technique resulting in a powder with the highest retention (86.2%) of d-limonene, mainly due to its capability to produce emulsions with fairly small droplets (d(43) of 700-800 nm) and narrow distributions, which had a good stability during the process. Among different emulsifiers used, although Tween 20 significantly reduced the emulsion size (d(43) < 200 nm), the resulted powder had the poorest encapsulation efficiency.