Ede, July 16 2018 — In a recent study, performed by scientists of NIZO, Sorbonne Universités Paris, Stony Brook University New York and Utrecht University, an initial step was taken towards understanding the complex dynamics of stabilizing emulsions with, for example, plant proteins, which do not dissolve in water.

Understanding the process

In this study, the process of adsorption of an individual micro particle at a liquid-liquid interface was followed in real time. Liquid-liquid interfaces are found in food emulsions, between oil droplets and the water phase. Examples are mayonnaise and dressings. Traditionally, these emulsions are stabilized by using whey or egg protein, or label-unfriendly surfactants. However, the recent interest in the use of plant proteins has focused attention on another way of stabilizing food emulsions: by micro particles made from aggregated plant protein.

Emulsions are made by homogenization of a mixture of oil and water. The events on a microscopic scale during homogenization are determined by the shear rate imposed on the oil droplets and adsorbing particles. In order to optimize the process of homogenization, it is necessary to know how fast particles adsorb at the oil-water interface. This work was carried out to investigate this.

For technical reasons, the measurements were actually carried out not with oil-water interfaces, but water-water interfaces, because the adsorption at water-water interfaces (between a protein and a polysaccharide solution) is much easier to study. Understanding this complex process is crucial for making stable emulsions in the food and health industry.

Application of this process

The practical application of this work is the availability of a technique to directly observe (with a microscope) the real-time adsorption of particles from various sources at liquid-liquid interfaces. It is well known that particles from different protein sources (e.g. zein, gelatin and gliadin) have widely different capacities to stabilize emulsions. From the type of observations produced in this work, it will become clear how to optimize the stabilization of food emulsions by label-friendly and environmentally-friendly plant protein particles. Hans Tromp, senior scientist protein functionality at NIZO: “For a broader application of novel plant protein-based stabilizers a revision of standard food processing operations may be necessary, to account for the different interactions and kinetics by which plant proteins operate.”

 Available online: https://doi.org/10.1103/PhysRevLett.120.208003

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