Encapsulation of olive leaf phenolics within electrosprayed whey protein nanoparticles; production and characterization

Nanoencapsulation is an emerging research field in different disciplines including food, pharmaceutical, and cosmetic industries. In this work, nanoparticles containing olive leaf extract (OLE) were prepared from whey protein concentrate (WPC) via electrospraying and the impact of core and wall concentration on the morphology, encapsulation efficiency, zeta potential, particle size, and polydispersity index (PDI) of capsules was studied. Also, chemical structure and phenolic profile of final nanocarriers was analyzed by Fourier-transform infrared spectroscopy (FTIR), and high performance liquid chromatography (HPLC), respectively. Our results showed that spherical nanoparticles were obtained through electrospraying and their size was dependent on applied levels of WPC and OLE. Encapsulation efficiency increased significantly (P < 0.05) at higher contents of OLE and WPC. All produced particles had a negative zeta potential. FTIR data revealed no new spectrum in the encapsulated samples and only a new peak (at 611.23 cm(-1)) was observed for 15% WPC particles containing 1000 ppm phenolics. The mean size of electrosprayed WPC nanoparticles was 232.3-659.8 nm with a PDI of 0.074-0.650, revealing a heterogeneous nanoparticle population. By increasing WPC (from 15% to 30%), smaller particles were observed with higher encapsulation efficiencies. Also, increasing the OLE (from 500 to 1000 ppm) resulted in bigger particles. HPLC analysis showed that nanocarriers of 15% WPC loaded with 500 ppm phenolics had the highest content of oleuropein (138 mg/kg), tyrosol (42 mg/kg) and caffeic acid (36 mg/kg); but the highest level of hydroxytyrosol (94 mg/kg) was found in particles with a composition of 15% WPC and 1000 ppm phenolics.