Moringa Oleifera Proteins as Pickering Stabilizers: From Nanostructures to Rheology

Substantial food waste as a result of chemical decay of food enormously impacts the environment, henceforth the need for stabilization by surfactants but the associated carbon footprints possess a threat to the industry. Thus, Pickering emulsions, stabilized by solid- particles, residing at droplet interfaces come into the picture, providing more stable systems than surfactants. In terms of resistance against fusion (coalescence) and coarsening (Ostwald ripening) Pickering emulsions are thermodynamically stable systems with good biocompatibility and can be utilized as carriers for delivery of bioactive compounds, thus applied in food to control and enhance texture and taste and improve stability¹.<br/>Plant proteins attract great interest and the stability of Pickering emulsions is governed by protein properties, protein concentration, and environmental factors. The Moringa protein has been chosen because it is inexpensive, with great nutritional benefits and wide availability, and has been scientifically proven to have excellent anti-oxidant, anti-hypertensive, and anti-diabetic properties².<br/>Protein particle interactions are very much dependent on pH. Such protein-based nanoparticles have proven to be advantageous as they are biodegradable, non-toxic, and provide the large possibility for surface modification³.<br/>All this motivates our study to investigate the Moringa protein as Pickering particles for emulsions fabricated at different pH and ionic strengths. The rheology and corresponding macroscopic gel properties of such emulsions can be designed by arrested coalescence for producing food spreads with desired rheological properties⁴. During this, aggregates are formed with the interaction between denatured non-absorbed proteins and absorbed ones at the emulsion droplet interfaces which can be impact from lipid oxidation, which influences emulsion particle interactions. Proteins can form gels after aggregation at different pH or ionic concentrations. It is difficult to separate the association mechanism of gelation and emulsification through protein aggregation⁵ which is another motivation for our studies.<br/>We have undertaken a program to distinguish the “good” and “not so good” Moringa-based protein stabilizers by utilizing microscopic observations and rheometry and using Small- Angle -X- ray-Scattering (SAXS) to examine structural stability and aggregations of the same stabilizing proteins, thus gathering information on protein⁶, and how this is connected to the rheological properties. Further works include formulating food spread using this emulsion and studying its smell and mouthfeel quantification.<br/><b>ACKNOWLEDGEMENTS:</b><br/>This work received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 956248.<br/><b>REFERNCES:</b><br/>1. Kargar, M., Fayazmanesh, K., Alavi, M., Spyropoulos, F. & Norton, I. T. Investigation into the potential ability of Pickering emulsions (food-grade particles) to enhance the oxidative stability of oil-in-water emulsions. <i>J Colloid Interface Sci</i> <b>366</b>, 209–215 (2012).<br/>2. Chen, L., Ao, F., Ge, X. & Shen, W. Food-grade pickering emulsions: Preparation, stabilization and applications. <i>Molecules</i> <b>25</b>, (2020).<br/>3. Tarhini, M. <i>et al.</i> Protein-based nanoparticle preparation via nanoprecipitation method. <i>Materials</i> <b>11</b>, (2018).<br/>4. Huang, Z. <i>et al.</i> Fabrication and stability of Pickering emulsions using moringa seed residue protein: Effect of pH and ionic strength. <i>Int J Food Sci Technol</i> <b>56</b>, 3484–3494 (2021).<br/>5. Zhu, Z. <i>et al.</i> Food protein aggregation and its application. <i>Food Research International</i> vol. 160 Preprint at https://doi.org/10.1016/j.foodres.2022.111725 (2022).<br/>6. Han, Q. <i>et al.</i> Small angle X-ray scattering investigation of ionic liquid effect on the aggregation behavior of globular proteins. <i>J Colloid Interface Sci</i> (2023) doi:10.1016/j.jcis.2023.05.130.