A two-step air classification and electrostatic separation process for protein enrichment of starch-containing legumes

Qinhui Xing,Dea Putri Utami,Marta Boronat Demattey,Konstantina Kyriakopoulou,Martin De Wit,Remko M Boom,Maarten A.I Schutyser

doi:10.1016/j.ifset.2020.102480

Qinhui Xing, Dea Putri Utami + Show 5 more

Open Access

https://doi.org/10.1016/j.ifset.2020.102480

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Abstract

A two-step dry fractionation process was investigated that further enriches protein from starch-containing legumes. Legumes (pea, lentil, and chickpea) were subjected to milling, air classification, and subsequent triboelectrostatic separation. The air classification first removes starch, whereas the subsequent electrostatic separation removes fiber from the resulting protein concentrate. Successful enrichment was achieved with pea and lentil, but this was not the case for chickpea due to the smaller starch granules and higher fat content. The best conditions for pea were air classification at an air-classifier wheel speed of 8000 rpm. Subsequently, electrostatic separation was optimized with two passes. With this, a protein purity was obtained of 63.4 g/100 g dry basis and a yield of 15.8 g/100 g dry solids. For the overall two-step dry fractionation process, a protein-enriched fraction with a yield of 4.0 g/100 g pea could be obtained, leading to 7.8% of total protein recovered from yellow pea. Industrial relevanceTo enrich protein from starch-containing legumes a novel dry method combining air classification and electrostatic separation was developed. Compared to conventional wet extraction, this dry route is much less energy-consuming and preserves the native functionality of the proteins. By adding electrostatic separation to air classification, a higher pea protein purity (up to 63.4–67.6 g/100 g) could be obtained, which is higher than that obtained by air classification only (57.1 g/100 g). It is estimated that for an improved dry fractionation process with increased recovery of material, the yield and protein recovery may be further increased with factor ~ 2.8 compared to the current results.

Highlights

Starch-containing grain legumes such as pea, chickpea, and lentils are a major source of dietary protein for over one billion consumers worldwide (Khazaei et al, 2019)
Starch granules are disclosed as larger particles; the proteins and fibers are primarily present as smaller fragments
Air classification was successfully applied to separate larger starch granules from smaller protein particles to produce starch and protein-enriched fractions from pea, navy bean, faba bean and lentil

Summary

Introduction

Starch-containing grain legumes such as pea, chickpea, and lentils are a major source of dietary protein for over one billion consumers worldwide (Khazaei et al, 2019). These legumes live in symbiosis with nitrogen binding bacteria in their root nodules, which reduces the need for artificial fertilizers compared to other plant protein sources. Starch obtains a similar polarity as the protein and is attracted to the same electrode as the protein, which impairs their separation This suggests a two-step approach by combining air classification and electrostatic separation to obtain pea protein concentrates with higher purity. This approach was only demonstrated using a lab-scale electrostatic separator in which yields could not be reported (P.J. Pelgrom, Wang, et al, 2015)

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