Effect of pH and Ionic Strength—Moringa Oleifera Protein Particles

Protein aggregation is a common phenomenon in food, significantly impacted by factors like particle size and shape. However, the exact mechanisms behind this process remain unclear. While protein aggregates can influence functional properties, food's inherent complexity further complicates aggregation behavior. Proteins naturally interact to form complex structures. However, these structures are vulnerable to stress, which can disrupt weak chemical bonds (non-covalent interactions) within the protein. This disruption can cause the protein to lose its secondary structure and clump together, forming aggregates[1]. While scientific studies on protein folding and aggregation often focus on isolated proteins, real food systems are far more complex. Instead of highly purified proteins, food contains a mixture of different proteins. This heterogeneity adds another layer of complexity to understanding how proteins aggregate[2].<br/>An interesting perspective emerges when comparing protein aggregation in biological systems (often viewed as "self-assembling" from a molecular chemistry standpoint) to food processing (considered "induced assembly" due to various physico-chemical conditions and external factors)[3]. The interplay between these factors in food requires further investigation. Therefore, elucidating the formation mechanism of protein aggregates and the factors influencing it is crucial for optimizing food quality and safety.<br/>The way proteins assemble in food is a delicate sway between two key factors: pH and ionic strength. Generally, a low concentration of charged molecules (ionic strength) favors the ordered formation of protein aggregates, while a high concentration leads to messy clumps (disordered precipitates). Similarly, a low pH (more acidic environment) often promotes the formation of stable protein aggregates[4]. This is because pH directly affects the electrical charge on protein molecules. Proteins have specific amino acids that can gain or lose charges depending on the surrounding pH. These changes influence how proteins interact with each other, impacting their final structure. pH and ionic strength can also influence the shape of the resulting aggregates. Studies by Amagliani & Schmitt (2017) have shown that different pH conditions can lead to diverse morphologies, ranging from neat spheres to flexible strands and even semi-rigid fibers[5].<br/>We believe that by understanding how pH and ionic strength influence protein aggregation, we can gain better control over the structure and function of these aggregates in food systems. To achieve this, we're investigating the aggregation of Moringa Oleifera seed protein particles by manipulating pH and ionic strength as driving forces. We employ Dynamic Light Scattering and Laser Diffraction to monitor changes in protein particle size as these factors are varied. These size measurements are further confirmed by advanced techniques like Small Angle X-Ray Scattering (SAXS) and X-Ray Photon Correlation Spectroscopy (XPCS). Raman and FTIR spectroscopy confirm the presence of proteins in our extracts. While the iodine test assures the absence of starch, the potential presence of other carbohydrates alongside proteins necessitates further investigation. Future studies will also focus on tuning the physicochemical properties of these aggregates through pH adjustments. This approach holds promise for enhancing their emulsifying properties, which could be valuable in food product development.<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>REFERENCES:</b><br/>[1] doi: 10.1093/femsre/fuz026.<br/>[2] doi: 10.1016/j.copbio.2014.08.001.<br/>[3] doi: 10.1371/journal.pone.0263693.<br/>[4] doi: 10.2147/IJN.S54171.<br/>[5] doi: 10.1016/j.tifs.2017.07.013.