In repulsive emulsions stabilized by ionic emulsifiers, oil droplets and their associated interfacial charge clouds can form a random jammed structure at a critical volume fraction, thereby forming an elastic material. In monodispersed emulsions, it is well known that the droplets are randomly jammed at an effective volume fraction of 0.64; however, the knowledge of the random jamming volume fraction (ϕMRJ) for polydisperse emulsions is limited. The present work aims to experimentally determine the relationship between polydispersity and ϕMRJ using a food-grade ionic emulsifier, citric acid esters of monoglyceride (CITREM)-stabilized canola O/W nanoemulsions, with an average droplet size of 236 nm and a relative polydispersity of 0.54. The nanoemulsions were size-fractionated using ultracentrifugation to obtain a range of average droplet sizes (272 to 360 nm) and relative polydispersity (0.26 to 0.43). The cream layers obtained from the ultracentrifugation were diluted with CITREM solution to obtain a range of oil volume fractions (ϕ) from 0.4 to 0.6 at various polydispersities, and their elasticity was determined, which showed an increase in plateau storage modulus (Gp′) with a decrease in oil droplet size and an increase in ϕ. The ϕMRJ of the size-fractionated nanoemulsion was predicted with the entropic, electrostatic, and interfacial (EEI) model for monodisperse emulsions with modified parameters, which successfully predicted the repulsive jamming transition in nanoemulsions and their ϕMRJ, establishing a relationship between relative polydispersity and ϕMRJ. Such a relationship would help predict the elasticity of repulsively jammed polydisperse nanoemulsions, enabling the rational design of emulsion-based food products with reduced oil content, improved stability, and enhanced rheological properties.
Patel et al. (Fri,) studied this question.