Oil/water surface rheological properties of hydroxypropyl cellulose (HPC) alone and mixed with lecithin: Contribution to emulsion stability

Hydroxypropyl cellulose (HPC) is a neutral branched polysaccharide derivatized from a wood substrate. Widely used in whipping vegetable creams, HPC is a thickening biopolymer having surface active properties both at air/water and oil/water interfaces. Myglyol/water interfacial rheology was used to characterize the behavior of HPC at this interface in the presence or the absence of lecithin, an emulsifier classically used in combination with HPC. Addition of HPC in the aqueous phase leads to an increase of the surface pressure at the oil/water interface depending on the HPC concentration. The higher the HPC concentration, the shorter is the lag time before the surface pressure increase. The equilibrium surface pressure is about 13–16 mN m−1 whatever the HPC concentration in the studied range. In order to understand the way the HPC positions itself at the interface, a viscoelastic characterization of the interface was performed during adsorption, in the presence and in the absence of lecithin. A comparison to the stability of emulsions containing HPC or HPC/lecithin is made and discussed using droplet size evolution and droplet displacement rate to an upper layer.