Tunable assembly of hydrophobic protein nanoparticle at fluid interfaces with tannic acid.

Interparticle forces that govern the assembly of particles adsorbed at fluid interfaces determine the rheology and microstructure of particle laden interface. In this study, natural small molecule, tannic acid (TA), was used to modify particle-particle interactions and assembly behaviors of food grade hydrophobic protein particle (zein nanoparticle) at air-water interface. For bare zein particle (ZP), the rapid adsorption and high interparticle forces led to the low coverage and formation of large ZP aggregates at the interface. The hydrogen-bonding of TA weakened the particle hydrophobicity and thus interparticle forces at fluid interfaces. Therefore, the adsorption process and assembly rate of ZTP at the interface obviously reduced, which also provided enough time for ZTP to rearrange into orderly interfacial networks. Furthermore, the Lissajous plots of surface pressure versus deformation are used to understand the surface rheological response to large mechanical deformation in terms of interfacial microstructure. The rheological response of interface stabilized by ZTP showed strain hardening during extension and strain softening during compression. These findings indicate that the interfacial rheology and microstructure of zein particle-laden interface can be tuned by changing the TA content. [ABSTRACT FROM AUTHOR]