Abstract

Cellulose-based oil-in-water (O/W) emulsions were studied by diffusing wave spectroscopy (DWS) regarding the effect of the cellulose concentration and mixing rate on the average droplet size, microrheological features and stability. Furthermore, the microstructure of these emulsions was imaged by cryo-scanning electron microscopy (cryo-SEM). The micrographs showed that cellulose was effectively adsorbed at the oil-water interface, resembling a film-like shell that protected the oil droplets from coalescing. The non-adsorbed cellulose that was observed in the continuous aqueous medium, contributed to the enhancement of the viscosity of the medium, leading to an improvement in the stability of the overall system. Generally, the higher the cellulose concentration and mixing rate, the smaller the emulsion droplets formed, and the higher was their stability. The combination of both techniques, DWS and cryo-SEM, revealed a very appealing and robust methodology for the characterization and design of novel emulsion-based formulations.

Highlights

  • Emulsions can be simplistically defined as dispersions of an immis­ cible liquid into another (Tadros, 2013)

  • We further explored the influence of cellulose concentration and mixing rate on the emulsions droplet size, microrheology, and stability

  • Cellulose-stabilized O/W emulsions were studied by diffusing wave spectroscopy (DWS) regarding the effect of the mixing rate and cellulose concentration on the emulsion average droplet size, microrheological properties and stability

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Summary

Introduction

Emulsions can be simplistically defined as dispersions of an immis­ cible liquid into another (Tadros, 2013). Emulsions can be categorized as oil-in-water (O/W) or water-in-oil (W/O), depending on the liquids that form the continuous and dispersed phases. The tuning of the physical properties of the emulsions, such as droplet size, flow behaviour and physical stability, are important to obtain a final product with superior characteristics (McClements & Gumus, 2016; Tadros, 2013). The study of the emulsions rheological behaviour is quite relevant, due to its intrinsic sensitivity to the oil and aqueous volume fractions, the size of droplets, and the physical features of the emulsifying agent (Corredig & Alexander, 2008; Tadros, 2013)

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