The under-recognized fundamental effects of component interaction and deformability for membrane processes for food

Membrane filtration plays a prominent role in the production of food ingredients. Currently, membranes are used at very large scale, and at relatively low energy input compared to other separation methods. For those mem-brane separation processes most relevant for food (micro, ultra, nanofiltration, and also reverse osmosis), membrane choice is based on component size relative to the pore size, often in combination with mass transfer considerations. What is missing are considerations related to the specific properties of the food ingredients, such as their deformability, which makes them stand out from other components.In this review, we distinguish processes used to concentrate (removal of low(er) molecular weight compo-nents), and to fractionate components (separation of components close in size leading to enrichment of one of the components present). For the latter option, deformability most probably plays a more prominent effect, since this co-determines the probability of passage/retention by a membrane that is relatively free of accumulated com-ponents; for concentration, accumulated components will enhance retention greatly, especially if they are deformable.In fundamental sciences, important hints are available that allow for estimation of effects related to deformability of components under conditions as would occur during filtration (pressure, flow etc.). A special class of tools to investigate these phenomena are microfluidic devices, the so-called micro-membranes, that can be used to emulate underlying mechanisms. From pioneering work, it became clear that flexible gel particles are able to pass constrictions/pores through shape changing, and deswelling, depending on the size of the particle, and the geometry of the pore. Furthermore, collective particle behaviour that may enhance (by migration in flow) as well as deteriorate separation by clogging have been reported. In the current review, we try to translate the learnings taken from there, to process design suggestions and guidelines.

Automated summary

Membrane filtration plays a crucial role in food ingredient production, but there is a lack of consideration for the specific properties of food ingredients. This review focuses on the processes of concentration and fractionation, highlighting the importance of deformability in membrane filtration.