Dry separation for sustainable processing of functional plant protein fractions

1. Dry separation for sustainable processing of functional plant protein fractions PhD. Student: MSc P.J.M. Pelgrom Phone: +31 317 485289 Thesis advisor: Prof. Dr. Ir. R.M. Boom E-mail: pascalle.pelgrom@wur.nl Supervisor: Dr. Ir. M.A.I. Schutyser URL: www.fpe.wur.nl Research group: Food Process EngineeringResearch school: VLAG Supported by: PEAS foundation, ISPT Period: Nov 2010 – Nov 2014 • Introduction • Novel protein foods based on plant proteins may provide a sustainable alternative to those based on animal-derived proteins. However, nowadays plant proteins are isolated by wet processing, requiring large amounts of water and energy. Moreover, wet isolation uses extreme conditions (i.e. high pH and T) that negatively affect (native) protein functionality. In this project, we aim at development of a sustainable dry separation route for processing of functional protein fractions using combined milling and air classification. • Protein enrichment by dry fractionation is facilitated by the particular architecture of the cotyledon of pulses. The cotyledon consists of small protein bodies and larger (>25µm) non-protein cell components, like starch in peas or fibres in lupine. During milling, the seed tissue is ruptured into fragments with different composition. By air classification, the flour obtained after milling can be separated into a fine and a coarse fraction (fig.1). The fine fraction is enriched in protein. • Fig.1. Schematic overview of the air classifier used in this study (ATP50). • Aim • The aims of this project are 1) to gain insight into optimal disentanglement of pulses by milling to facilitate dry fractionation, 2) to develop dedicated procedures to optimally dry fractionate plant proteins, and 3) to analyse the (native) functionality of the obtained fractions. • Results • Successful dry fractionation requires optimal fracture behaviour of the cotyledon. Depending on the state (glassy vs. rubbery) of the protein bodies and starch granules it was found that fragmentation lines were different. Under specific conditions the fracture lines coincided with the contact lines between starch granules and protein bodies 1. Subsequently, optimal milling conditions were explored that provided not too fine milling (providing particles of similar size) or too coarse millings. Optimal milling yielded after air classification protein fractions with 55% protein (w/dw) with a protein recovery of 29%. The native functionality of the protein fractions was demonstrated by its ability to form a liquid concentrate upon addition of water 2. • Lupine beans have a different morphology and require coarse milling. Air classification yielded protein fractions with 59% protein (w/dw) and a protein recovery of 16%. The dispersibility was negatively affected by the high lipid content of lupine. Addition of aerosil was found to enhance the dispersibility of lupine flour and thereby the yield of the protein fraction. • Conclusions • Dry fractionation is a promising technique for the processing of functional pea and lupine protein fractions. While conventional wet isolation focuses on molecular purity, dry separation delivers native functional fractions. • Acknowledgement • This research project is carried out within the framework of ISPT and is financially supported by the PEAS foundation. • References • 1P.J.M. Pelgrom, M.A.I. Schutyser, R.M. Boom. 2012. Food and Bioprocess Technology, DOI 10.1007/s11947-012-1031-2 • 2P.J.M. Pelgrom, A.M. Vissers, R.M. Boom, M.A.I. Schutyser. 2013. Food Research International. 53 (1): 232–239