The effect of diesters and lauric acid on rheological properties of air/water interfaces stabilized by oligofructose lauric acid monoesters.

In this study, the rheological properties of interfaces stabilized by oligofructose fatty acid esters were elucidated. First, the properties of interfaces stabilized by monoesters (ME), diesters (DE), lauric acid (LA), oligofructose (OF), and mixtures of ME with DE, LA, or OF were studied. Second, the properties of interfaces stabilized by the crude product (CP) containing ME, DE, LA, and OF were studied. The dependency of the dilatational modulus on frequency and deformation amplitude indicated the possible formation of a soft glass phase for ME, and a viscous interface for DE. When ME and DE were mixed at a ratio of 0.8/0.2, the experimental results suggest that the interfacial structure consists of islands of a glass phase formed by ME, dispersed in a 2D viscous phase of DE. CP stabilized interfaces, where the ratio ME/DE was higher, lead to a different rheological response. The ratio ME/DE plays an important role in the surface properties of the CP. This may have significant consequences for applications in macroscopic systems such as foams.