Lipid emulsions rheology

Micronization is an optional process that helps to reproduce the fatty sensation afforded by polysaccharides. The 0.2-nm particles in Avicel (FMC, 1993) and the 1-5-nm particles in the rice mimetic (Pszczola, 1991) simulate lipid emulsion rheology as well as lipid oral sensations. The simulation mechanism implicates a weak gel structure and an expansive surface where a large volume of water is immobilized. 

Wasan and his research group focused on the field of interfacial rheology during the past three decades [15]. They developed novel instruments, such as oscillatory deep-channel interfacial viscometer [20,21,28] and biconical bob oscillatory interfacial rheometer [29] for interfacial shear measurement and the maximum bubble-pressure method [15,29,30] and the controlled drop tensiometer [1,31] for interfacial dilatational measurement, to resolve complex interfacial flow behavior in dynamic stress conditions [1,15,27,32-35]. Their research has clearly demonstrated the importance of interfacial rheology in the coalescence process of emulsions and foams. In connection with the maximum bubble-pressure method, it has been used in the BLM system to access the properties of lipid bilayers formed from a variety of surfactants [17,28,36]. 

The interfacial rheology of protein adsorption layers has been intensively studied in relation to the properties of foams and emulsions stabilized by proteins and their mixtures with lipids or surfactants. Detailed information on the investigated systems, experimental techniques, and theoretical models can be found in Refs. [762-769]. The shear rheology of the adsorption layers of many proteins follows the viscoelastic thixotropic model [770-772], in which the surface shear elasticity and viscosity depend on the surface shear rate. The surface rheology of saponin adsorption layers has been investigated in Ref. [773]. 

Lipid thickeners, e.g. waxes, are also used in cosmetic formulations as rheology modifiers. They also form water-repellent films and improve the smoothness and texture of emulsions. Silica or polyethylene are used to formulate anhydrous lipogels. 

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