A large decrease in permeability is often observed during the filtration of nano-sized colloids, while fouling is widely regarded as the main explanation for this phenomenon. The osmotic pressure or concentration polarization (CP) of colloids can also contribute to the flux decline. However, the contribution of CP to flux loss cannot be determined by the traditional CP model. In this study, the effect of fouling and CP/osmotic pressure on flux was distinguished. The CP values of polyethylene glycol (PEG) and silica-colloids were determined by the osmotic pressures near the membrane surface and in the feed. The CP induced by colloids accounted for 43–95% of the flux loss in our experiments. Silica exhibited higher CP values (127–460), compared to 7–71 for PEG. This was attributed to the slower back diffusion caused by the larger colloids, as evidenced by the diffusion coefficients of 4.30 × 10⁻¹¹ m²/s for silica (10 nm) and 1.45 × 10⁻¹⁰ m²/s for PEG (2.9 nm). Although the CP was mitigated by increasing the cross-flow velocity, CP values of 31 and 250 were observed for PEG and silica at high Reynolds number of 7317, respectively. The experimentally obtained CP values were also compared with those calculated by the film diffusion model.

Currently, plant proteins are fractionated to ingredients with high purities, but an often ignored point is the impact of the extraction and fractionation process on protein functionality. To allow a fair and effective comparison, it is key to understand the changes in protein's aggregated state occurring in the extracted ingredients during processing. We review conventional and upcoming plant protein extraction and fractionation processes (on pulses and oilseeds) and focus on how the processing history influences the macroscopic functional properties of the proteins. To establish this link, we dive into seed morphology and give an overview of the plant seed composition. In addition, we explain the essence of each process step and how it impacts the protein's aggregated state. The latter is linked to the macroscopic functionality (foaming, emulsification, and gelation). We identified three major protein structure-changing steps in the conventional protein extraction process: defatting, alkaline extraction, and isoelectric point precipitation. These steps lead to large, insoluble aggregated structures, which strongly impacts the protein macroscopic functionality. Milder extraction methods reduce these alterations, but a potential consequence is the presence of non-proteinaceous components, which could give challenges in sensory and nutritional aspects and affect the techno-functional properties of the ingredient. The take-home-message is that we need to consider the process-induced change of the protein aggregated structures, which are likely to dominate the functionality over the protein's molecular parameters.