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

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 relevance: To 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.