Influence of the ratio of amphiphilic copolymers used as emulsifiers on the microstructure, physical stability and rheology of α-pinene emulsions stabilized with gellan gum

•We study the Atlas™ G-5000/Atlox™ 4913 mass ratio to obtain O/W emulsions.•Atlas™ G-5000 copolymer is essential to obtain significantly stable emulsions.•Polarizing microscopy supports the presence of the latter at the droplet interface.•The emulsions show mechanical spectra typical of faintly structured materials.•Destabilization of the studied emulsions is monitored by MLS results. α-Pinene is a terpenic solvent whose use in the formulation of emulsions entails a double benefit from the environmental point of view since it is a green solvent, easily biodegradable, which also has certain antimicrobial properties. In this work a combination of Atlas™ G-5000 and Atlox™ 4913 amphiphilic copolymers was used to obtain O/W emulsions formulated with α-pinene and gellan gum. These emulsions may find applications related to the design of complex biotechnological systems with different uses. In order to investigate the microstructure and the physical stability of these emulsions, a combination of different techniques such as rheology, microscopy, laser diffraction and multiple light scattering turn out to be a useful methodology. The results demonstrated the need to include a minimum amount of Atlas™ G-5000 copolymer in the formulation of these emulsions to improve their stability. These results were supported by the information revealed by optical micrographs, according to which Atlas™ G-5000 is directed to the continuous medium to structure water (this surfactant is particularly effective at forming hydrogen bonds with water). On the other hand Atlox™ 4913 is preferentially adsorbed at the α-pinene–water interface, such that a high Atlox™ 4913/Atlas™ G-5000 mass ratio slows down the kinetics of coalescence as shown by multiple light scattering. However, a very low relative concentration of Atlas™ G-5000 causes creaming to become the dominant destabilization mechanism. Increasing the Atlas™ G-5000/Atlox™ 4913 mass ratio yields emulsions with enhanced viscosity and viscoelasticity.