Sensory perception of emulsion-based food systems as well as the bioavailability of nutrients contained are determined by underlying physicochemical properties, altering for example digestibility, stability, appearance, sensory and rheological properties.
The particular colloidal structure of foods needs to be specifically assembled to deliver the desired performance, such as specific rheological properties. The aim of the current study focuses on the screening and formation of electrostatically charged food- and cosmetic-grade surfactants in order to prepare positively and negatively charged oil-in-water emulsions, which are then mixed together to induce controlled heteroaggregation of the oil droplets with changed rheological characteristics. Additionally, the development of new food structures or “smart” (responsing) materials might be possible, since floc formation is highly dependent on colloidal interactions. By changing the environmental conditions such as pH and/or ionic strength the electrostatic forces acting between oppositely charged particles are strongly affected.
However, knowledge on the heteroaggregation behavior of oppositely charged food- or cosmetic-grade emulsions is still scarce. In our study, a screening with food- and cosmetic-grade surfactants was initially conducted to determine oppositely charged emulsion pairs, which are stable in terms of coalescence under specific environmental conditions. Therefore, electrostatically charged low (esterified fatty acid surfactants, saponin, betaines, quaternary ammonium salt) and high molecular (whey protein, casein, fish gelatin and pectin) surfactants were chosen to form O/W emulsions (φ = 0.1) by high shear-blending and subsequent ultrasonication to yield oil droplets in the submicron range (d ≈ 1.5µm) at pH 3 and 7.
Minimal surfactant concentrations, surface charges, particle size distributions, visual observations, and rheological behavior of these initial emulsions were determined. The results of the initial emulsion screening showed appreciable differences (e.g. surface charges for negatively charged surfactants at pH 3: -11.0 to -71.1 mV; pH 7: -24.4 to -87.0 mV), which might significantly influence the heteroaggregation process and the heteroaggregate stability towards coalescence, which will be examined in a following study.
Research Supervisor: Prof. Jochen Weiss j.weiss@uni-hohenheim.de
