Preparation of whey protein nanoparticles via antisolvent precipitation technique and their applications in nanoencapsulation of comomile extract

An alkaline solution of whey protein isolate was charged with absolute ethanol resulting in precipitation of whey proteins as nanoscalar core-free particles or extract-loaded particles. An encapsulation efficiency of ~81% was obtained in 1:20 mass ratio of extract-to-WPI. Fourier transform infrared spectroscopy suggested that extract and whey proteins interacted via hydrogen bonds and hydrophobic interactions. The enzyme transglutaminase-induced cross-linking was employed to inter-connect the whey proteins after which ethanol was added to protein solution in order to desolvate the medium and generate whey protein nanoparticles. Light scattering measurement of the hydrodynamic size of particles showed a bimodal pattern for all samples comprised from two populations with different median sizes. Atomic force microscopy indicated a lower height for the particles from enzymatically cross-linked proteins. In-vitro degradation of whey protein nanoparticles in a simulated gastric fluid demonstrated that cross-linking of whey proteins before desolvation stage enhanced significantly the digestion stability of particles. However, a reinforcing effect on particles was suggested for cross-linking based on the in vitro tests carried out at various digestion media. Cross-linking slowed down the release rate of entrapped extract from particles in a simulated gastric fluid