Preparation of walnut protein isolate-galactooligosaccharides composite nanoparticles and properties of their Pickering emulsion
Walnut protein-galactooligosaccharides(WalPI-GOS)composite nanoparticles were synthesized from WalPI and GOS by pH cycling and ultrasound,characterized by FTIR,nanoparticle size and Zeta potentiometer,ultraviolet-visible spectrophotometer,fluorescence spectrophotometer and DSC,and then mixed with tea oil to obtain Pickering emulsions.The effects of m(WalPI)∶m(GOS)on the properties of WalPI-GOS and Pickering emulsion were further investigated.The result showed that the WalPI-GOS composite nanoparticles and Pickering emulsion exhibited the best properties when m(WalPI)∶m(GOS)=10∶4.The WalPI-GOS composite nanoparticles displayed an average particle size,Zeta potential,emulsifying activity index and emulsion stability index of 82.08 nm,-52.37 mV,31.12 m2/g,and 4346.35 min,respectively.The embedding of partial WalPI hydrophobic groups in WalPI-GOS molecules led to reduction in the surface hydrophobicity of WalPI-GOS(840.81 a.u.)and increment in the free sulfhydryl content(8.78 μmol/g)as well as melting temperature(93.74℃).The complexation of WalPI and GOS changed the secondary and tertiary structure of WalPI and formed a secondary structure dominated by β-folding.WalPI and GOS formed a compact network structure by hydrogen bonding,electrostatic interaction,and hydrophobic interaction.Pickering emulsion exhibited a particle size of only 5.24 μm,uniform droplet distribution,and an elastic gel network structure,while displayed the highest apparent viscosity of 1.06 Pa·s at a shear rate of 0.1 s-1.The high cross-linking density between WalPI and GOS enhanced the gel network structure of Pickering emulsion.
walnut protein isolategalactooligosaccharidescomposite nanoparticlesPickering emulsionsstabilityfood chemicals
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