核桃蛋白-低聚半乳糖复合纳米颗粒的制备及其Pickering乳液性质

Preparation of walnut protein isolate-galactooligosaccharides composite nanoparticles and properties of their Pickering emulsion

以核桃蛋白(WalPI)和低聚半乳糖(GOS)为原料,采用pH循环-超声联合制备了WalPI-GOS,将其与茶油混合,制备了Pickering乳液。通过FTIR、纳米粒度及Zeta电位仪、紫外-可见分光光度计、荧光分光光度计、DSC对WalPI-GOS进行了表征,考察了m(WalPI)∶m(GOS)对WalPI-GOS颗粒特性及Pickering乳液性质的影响。结果表明,当m(WalPI)∶m(GOS)=10∶4时,WalPI-GOS和Pickering乳液具有最佳的性能。WalPI-GOS的平均粒径为82.08 nm,Zeta电位为–52.37 mV,乳化活性、乳化稳定性为31.12 m^(2)/g和4346.35 min;WalPI部分疏水基团被包埋于WalPI-GOS分子内部,降低了表面疏水性(840.81 a.u.),提高了游离巯基含量(8.78μmol/g)和熔融温度(93.74℃);WalPI与GOS的复合改变了WalPI的二级和三级结构,形成以β-折叠为主的二级结构,WalPI与GOS通过氢键、静电相互作用和疏水相互作用形成紧密的网络结构;Pickering乳液平均粒径仅为5.24μm,液滴均匀分布,形成了弹性凝胶网络结构;当剪切速率为0.1 s^(–1)时,具有最高的表观黏度(1.06 Pa·s)。WalPI与GOS间的高交联密度增强了Pickering乳液的凝胶网络结构。

Walnut protein-galactooligosaccharides(WalPI-GOS) composite nanoparticles were synthesized from Wal PI and GOS by p H 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(Wal PI)∶m(GOS) on the properties of Wal PI-GOS and Pickering emulsion were further investigated.The result showed that the Wal PI-GOS composite nanoparticles and Pickering emulsion exhibited the best properties when m(Wal PI)∶m(GOS)=10∶4.The Wal PI-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 m^(2)/g,and 4346.35min,respectively.The embedding of partial Wal PI hydrophobic groups in Wal PI-GOS molecules led to reduction in the surface hydrophobicity of Wal PI-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 Wal PI and GOS changed the secondary and tertiary structure of Wal PI and formed a secondary structure dominated by β-folding.Wal PI 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 Wal PI and GOS enhanced the gel network structure of Pickering emulsion.