Dry & Hybrid Fractionation for Plant-Based Ingredients

Current plant processing technologies aim at production of food ingredients of high purity, because this is convenient in terms of product formulation. However, production of highly pure ingredients comes at the cost of relatively low yields and resource intensive processing. Chemicals and water are used to extract food components from plant matrices, after which high drying energy input is required to obtain a powdered ingredient. Furthermore, application of chemicals and heat negatively impacts the functionality of these ingredients. Upon formulation of foods, this may result in a need for additives in order to achieve desired properties.

The alternative is dry fractionation: plants are milled in order to disentangle the components, followed by separation step(s) that split the milled feed into selectively enriched fractions. At Wageningen University, Air Classification (AC) and Electrostatic Separation (ES) are used for this purpose. AC separates components based on differences in density and particle size, while ES is driven by differences in the charge of components. Because chemicals, water and drying (energy) are not involved, these dry fractionation processes are more sustainable and native functionalities of components are preserved to a greater extent.  

Dry fractionation is suitable for crops with a low intrinsic moisture content. Therefore, in this research, applications of AC and/or ES are studied with respect to fractionation of barley, maize and legumes (pea, faba bean and chickpea).

With regard to barley and maize, dry fractionation is focused on separation of soluble and insoluble material prior to brewing. Early removal of insoluble matter reduces the formation of brewers’ spent grain and instead opens up possibilities for valorisation of a dry, fibre-enriched fraction. Moreover, loss of starch to the removed fractions is to be minimised in order to maintain a high brewing yield.

Legumes contain considerable amounts of protein, and conventional isolation methods heavily rely on wet processing involving chemicals. This project aims to obtain fractions enriched in protein or starch by AC and/or ES, followed by additional mild wet processes to increase their purities. This approach has been shown to combine fairly high protein yields (> 60%) and purities (> 70%) for pea fractionation on lab-scale. The next step is upscaling of this hybrid process; its application would strongly benefit the sustainability of plant protein ingredients.

This PhD project is a collaboration between the Laboratories of Physics and Physical Chemistry of Foods (FPH) and Food Process Engineering (FPE). It is part of the Sustainable Food Initiative ( and funded by TKI Agri&Food.