Adsorption Kinetics and Interfacial Dilatational Rheology of Oil–Water Interfacial Films Loaded with Homogalacturonan and Rhamnogalacturonan-I

Our recent study on the isolation of rhamnogalacturonan-I (RG-I) pectin enriched with acetyl groups, ferulic acid, neutral sugar side chains, and proteins through enzymatic hydrolysis of the homogalacturonan (HG) region of sugar beet pectin showed that RG-I molecules can form more stable emulsions than HG molecules. In this experiment, the interfacial adsorption kinetics of HG and RG-I molecules at the oil–water interface and the resistance effects of these interfacial films on extrinsic perturbations were further investigated. All of these experimental results indicated that the RG-I-stabilized interfacial film presented better elasticity (43.36 mN/m) and stronger resistance to extrinsic perturbations than HG (12.41 mN/m). In addition, both HG- and RG-I-loaded interfacial films exhibited linear viscoelastic responses when a small interfacial deformation and low-frequency perturbation were applied. When the interfacial deformation increased further, both HG- and RG-loaded interfacial films underwent strain softening during the extension stage. However, in the compression stage, the HG-loaded interfacial film underwent strain hardening, whereas the RG-loaded interfacial film exhibited strain softening.