Effect of tube wall material on electrostatic separation of plant raw‐materials

Qinhui Xing,Konstantina Kyriakopoulou,Martin De Wit,Maarten A I Schutyser,Remko M Boom

doi:10.1111/jfpe.13575

Qinhui Xing, Konstantina Kyriakopoulou + Show 3 more

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https://doi.org/10.1111/jfpe.13575

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Abstract

AbstractThe influence of charging tube materials and diameter on the separation efficiencies of a gluten‐starch model mixture and lupine flour was studied. Offline analysis of tribo‐charging with different tube materials showed that gluten takes a positive and starch a negative charge. However, the charge of the mixture was found not equal to the sum of the charge of the individual components and measured charges could not be related to the triboelectric series. During electrostatic separation significant protein enrichment was observed for both plant raw‐materials. For the model mixture differences in protein, enrichment were observed between tube materials, but this was not the case for lupine flour. The lupine protein content increased from 37 to 65 g/100 g dry flour. Concluding, electrostatic separation needs to be evaluated during separation experiments, as particle‐particle interactions dominate the charging process and thus separation of mixtures.Practical applicationsThe combination of dry milling and electrostatic separation is investigated as a sustainable and mild route for protein fractionation. The results of this study showed that offline charging tube experiments could not predict separation performance of for example finely milled lupin flours. Instead, performance should be directly assessed during separation experiments, which is explained as charging is rather related to differences in material or triboelectric charging properties between powder particles than to charging tube wall properties. The results of this study benefit development of new applications for electrostatic separation.

Highlights

The growing world population leads to a rapidly increasing demand for protein, while the potential of our planet to produce foods may well decline due to changes in the global climate (Asseng et al, 2015)
The tribo-charging in the different tubes was evaluated by analysis of the charge to mass ratio for gluten, starch, and the model mixture using a Faraday cup (Figure 4)
Charging tubes made from stainless steel, aluminum, PTFE, and Nylon were used to charge pure gluten, wheat starch, their mixtures, and lupine flour

Summary

Introduction

The growing world population leads to a rapidly increasing demand for protein, while the potential of our planet to produce foods may well decline due to changes in the global climate (Asseng et al, 2015). The current plant protein production needs to become more efficient. This can be done by shifting to more plant-based diets and by developing more efficient protein isolation routes (Aiking, 2011). Traditional wet protein isolation processes generally aim at high purity (> 90% protein) and are intensive in their use of water and energy. The native functional properties of proteins are often lost due to harsh processing conditions. Dry fractionation, which involves the combination of dry milling and dry separation, is proposed as a sustainable and mild route for protein fractionation. Dry fractionation provides less pure but highly functional protein-rich ingredients (Schutyser, Pelgrom, Van der Goot, & Boom, 2015), which has been demonstrated for various seeds of cereals and pulses (Schutyser & Van der Goot, 2011).

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