Study of the properties and colloidal stability for the technological application of zein-based nanospheres

Nanospheres of α-zein fabricated by antisolvent precipitation are promising carriers for hydrophobic bioactives in foods. The objective of this research was to study the changes in the properties of zein nanoparticles (size, ζ-potential, PDI, loading efficiency and pH colloidal stability) by using different copolymer coatings (sodium caseinate and pectin), ethanol concentrations (75 to 95% v/v) and solvent/antisolven or zein/krill oil ratios. Smallest particles (< 200 nm) can be obtained with the use of sodium caseinate as coating. This is the first time that zein nanospheres are used as encapsulating agents for a krill oil extract. These nanoparticles with a ζ -potential value around -25 mV are stable at neutral to basic pH values based on their ζ -potential and visual analysis. The use of pectin as coating produced the largest particles (< 400 nm) indicating that an increase in hydrophobic interactions allows the formation of bigger assemblies. Pectin-coated nanoparticles increased the LE of krill oil in about 9% compared with non-coated particles. Moreover, the krill oil/zein ratio was found to be a suitable way to increase the LE of the nanoparticles. The encapsulation of krill oil within the zein nanoparicles improved the antioxidant activity of the particles (noncoated and casein-coated particles). All types of nanoparticles were capable to nano-entrap appreciable amounts of a hydrophobic krill oil extract.