title: Recovery of protein from green leaves: Overview of crucial steps for utilisation.
abstract: Plant leaves are a major potential source of novel food proteins. Till now, leaf protein extraction methods mainly focus on the extraction of soluble proteins, like rubisco protein, leaving more than half of all protein unextracted. Here, we report on the total protein extraction from sugar beet leaves (Beta vulgaris L.) by a traditional thermal extraction method consisting of mechanical pressing, heating to 50 °C and centrifugation. The resulting streams (i.e. supernatant, green-protein pellet and fibrous pulp) were characterised in terms of composition, physical structure and processing options. The protein distributed almost equally over the supernatant, pellet and pulp. This shows that thermal precipitation is an unselective process with respect to fractionation between soluble (rubisco) and insoluble (other) proteins. About 6% of the total protein could be extracted as pure rubisco (90% purity) from the supernatant. Surfactants commonly used for protein solubilisation could hardly re-dissolve the precipitated proteins in the pellet phase, which suggested that irreversible association was induced between the co-precipitated proteins and cell debris. Thus, the extraction of this protein will require prevention of their co-precipitation, and should take place in the original juice solution.
authors.affiliation: Laboratory of Food Process Engineering, Wageningen University, PO Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: Angelica
authors.initials: A
authors.lastname: Tamayo Tenorio
authors.affiliation: Laboratory of Food Process Engineering, Wageningen University, PO Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: Jarno
authors.initials: J
authors.lastname: Gieteling
authors.affiliation: Netherlands Organisation for Applied Scientific Research - TNO, PO Box 360, 3704 HE Zeist, The Netherlands.
authors.forename: Govardus A H
authors.initials: GAH
authors.lastname: de Jong
authors.affiliation: Laboratory of Food Process Engineering, Wageningen University, PO Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: Remko M
authors.initials: RM
authors.lastname: Boom
authors.affiliation: Laboratory of Food Process Engineering, Wageningen University, PO Box 17, 6700 AA Wageningen, The Netherlands. Electronic address: atzejan.vandergoot@wur.nl.
authors.forename: Atze J
authors.initials: AJ
authors.lastname: van der Goot
mesh_terms: D027461:Beta vulgaris / Q000737:chemistry*; D005591:Chemical Fractionation; D004043:Dietary Fiber / Q000032:analysis*; D018515:Plant Leaves / Q000737:chemistry*; D014674:Plant Proteins, Dietary / Q000032:analysis*; D012273:Ribulose-Bisphosphate Carboxylase / Q000032:analysis*; D012995:Solubility
chemical_list: D004043:Dietary Fiber; D014674:Plant Proteins, Dietary; D012273:Ribulose-Bisphosphate Carboxylase
keywords: Dry matter composition; Leaf biorefinery; Membrane proteins; Protein extraction