Lupine protein enrichment by milling and electrostatic separation

Abstract

Abstract Lupine seeds are excellent source of plant protein. We here report on dry fractionation by combining milling and electrostatic separation providing an alternative to wet extraction of protein from lupine seeds. Relatively coarse milling was preferred as this provides sufficient detached protein bodies with less agglomeration of particles. After a single separation step a fraction with protein content 57.3 g/100 g dry solids was obtained. After three successive steps protein content was increased further to 65.0 g/100 g dry solids. By extra milling and recycling the fractions with comparable protein content as the flour, yield was improved without compromising protein content. A final fraction with protein content 65.1 g/100 g dry solids and yield of 6% was obtained, which means 10% of protein in the flour was recovered. Based on our findings an optimised scheme for protein enrichment from lupine seeds by combining milling and electrostatic separation is proposed. Industrial relevance Lupine seeds are an excellent source of plant protein. Wet extraction of protein from lupine seeds consumes large amounts of water and energy. Alternatively, dry fractionation is more sustainable and retains the native functional properties of the protein. Previously, it was shown that dry milling and electrostatic separation could be used to further enrich protein from lupine flour. In this study, the process was further investigated with a new custom-build bench scale electrostatic separator. We found that a lupine protein concentrate could be obtained with higher purity compared to conventional air classification and earlier lab-scale experiments. Subsequently, a scheme was developed to improve the yield of the lupine protein concentrate without compromising the purity, and this provides a guideline for scaling-up this technique for industrial application.