Rheological Properties and Microstructure of Canola-Based Emulsions Stabilized with Polyoxyethylene Sorbitan Surfactants_ Crimson Publishers

Rheological Properties and Microstructure of Canola-Based Emulsions Stabilized with Polyoxyethylene Sorbitan Surfactants by Gerson Lopes Teixeira* in Research & Development in Material Science_ journal of materials science and technology

 

Abstract
This work evaluated eight different emulsions produced with canola oil and stabilized using two different polyoxyethylene sorbitan surfactants (Tween® 60 or Tween® 85), by evaluating their microstructure and rheological properties. The results showed that the canola-based emulsion behaved as non-Newtonian fluids with pseudoplastic character (n or nH <0.7). Additionally, the Ostwald-de Waele (OW) and Herschel-Bulkley (HB) models adequately described the rheological behavior of the emulsions (R2 >0.98 for OW, and R2 >0.99 for HB; χ2 <0.001 for both), highlighting that the samples containing Tween® 60 (A, C, E and G) achieved higher values for the consistency coefficient (K <18.5) than the Tween® 85-based samples (B, D, F and H) (K <5.3), agreeing with the apparent viscosity data. Emulsions containing Tween® 60 at all concentrations and stirring rate conditions achieved the lowest droplet sizes (90% droplet size distribution (DSD) up to 4.0μm), higher consistency, and a global appearance similar to that of mayonnaise, while formulations made with Tween® 85 produced emulsions with bigger values for DSD, more fluid-like appearance and larger droplet sizes. In general, canola-based emulsions containing Tween® 60 showed better overall performance in the assays.

Introduction
One of the most important physical properties of dispersion samples is the particle size, which influences many other characteristics, being a valuable indicator of quality and performance for products such as suspensions, emulsions, and aerosols [1,2]. For these and many other reasons, it is important to measure and control the particle size distribution of those products. In addition, several imaging techniques and software are available to evaluate the structure of particulate systems, such as emulsions [3]. A wide variety of foods are emulsions: mixtures of two inherently immiscible fluids, one of which is the continuous, while the other is the dispersed phase [4]; thus, it is important to understand their physical, rheological and microscopic properties aiming to choose the best surfactants and process conditions to work with this colloidal system [1]. Additionally, the image processing and evaluation becomes important because it provides significant quantitative data of the micro/nanostructure of the dispersions [5], a key element in product development

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