Pulsed electric field pretreatment of rapeseed green biomass (stems) to enhance pressing and extractives recovery X. Yu, T. Gouyo, N. Grimi ⇑ , O. Bals, E. Vorobiev Sorbonne Universités, Université de Technologie de Compiègne, Laboratoire Transformations Intégrées de la Matière Renouvelable (UTC/ESCOM, EA 4297 TIMR), Centre de Recherche de Royallieu, CS 60319, 60203 Compiègne Cedex, France highlights  PEF pretreatment as a new way for the rapeseed biomass valorization was studied.  Juice expression yield and extractives recovery were enhanced after PEF pretreatment.  PEF pretreatment permitted to obtain higher consolidation coefficient b.  Press cake obtained after PEF assisted pressing was well dehydrated.  Negative impacts of advanced plant maturity on the PEF pretreatment efficiency were observed. article info Article history: Received 27 June 2015 Received in revised form 14 August 2015 Accepted 17 August 2015 Available online 28 August 2015 Keywords: Rapeseed Polyphenols and proteins extraction Pulsed electric field Compression behavior Diffusion abstract The objective of this study was to investigate the effects of pulsed electric field (PEF) pretreatment on the valorization of extractives (proteins and polyphenols) from rapeseed green biomass (stems) by pressing. The effect of pressure, electric field strength and pulse number on the juice expression yield, total polyphenols and total proteins content in the expressed juices were studied. Experiments conducted under optimal conditions (E = 8 kV/cm, t PEF = 2 ms, P = 10 bar) permitted to increase the juice expressed yield from 34% to 81%. Significant increases in total polyphenols content (0.48 vs. 0.10 g GAE/100 g DM), in total proteins content (0.14 vs. 0.07 g BSA/100 g DM) and in consolidation coefficient (9.0  10 8 vs. 2.2  10 8 m 2 /s) were also observed after PEF pretreatment. The recovered press cake was well dehydrated with an increase of dry matter content from 8.8% to 53.0%. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction Rapeseed stem is a green biomass feedstock generated from the rapeseed oil production. In some countries, most of this biomass is burned to air resulting in severe environmental problems. The emission of CO 2 , CH 4 and N 2 O during burning was confirmed to be a major source of greenhouse gases. Burning of rapeseed stems also causes loss of a potential carbon feedstock (Jain et al., 2014). Due to these problems, an alternative way to recycle these residues is to bury them in the field as soil amendment and fertilizer (Boydston and Hang, 1995). Rapeseed stems contain cellulose, hemicellulose, lignin, proteins and some low molecular weight compounds such as polyphenols (Housseinpour et al., 2010; Farag et al., 2013). The lignocellulosic part of rapeseed stems (cel- lulose, hemicellulose and lignin) has been used for the production of bioethanol as a sustainable alternative to fossil energy sources (López-Linares et al., 2015; Lu et al., 2009). However, reports deal- ing with the valorization of extractives (proteins and polyphenols) from rapeseed stems are really rare. Extraction by pressure (pressing) and extraction by solvent (diffusion) are two techniques widely used for oil and juices production, and biological waste valorization (Beveridge, 1997; Laufenberg et al., 2003). To facilitate the mass transfer from cellular tissue to surroundings, solid–liquid extraction is usually combined with pretreatments such as mechanical (cutting and grinding), thermal (heating and freezing–thawing), chemical and enzyme (Vishwanathan et al., 2011; Chung et al., 2013; Borrega et al., 2013; Sekhon et al., 2015). However, these traditional pre- treatment methods present certain disadvantages. For example, mechanical and thermal pretreatments usually lead to an increase in energy consumption and a decrease in extract purity due to the non-selective release of intracellular compounds. Chemicals and enzymes addition may cause environmental problems. http://dx.doi.org/10.1016/j.biortech.2015.08.073 0960-8524/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +33 3 44 23 44 42. E-mail address: nabil.grimi@utc.fr (N. Grimi). Bioresource Technology 199 (2016) 194–201 Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech