A comparative study of physical pretreatments for the extraction of polyphenols and proteins from vine shoots Hiba N. Rajha a,b , Nadia Boussetta b, ⁎, Nicolas Louka a , Richard G. Maroun a , Eugene Vorobiev b a UTC/ESCOM, EA 4297 TIMR, Département de Génie des Procédés Industriels, Laboratoire Transformations Intégrées de la Matière Renouvelable, Université de Technologie de Compiègne, Centre de Recherche de Royallieu, BP 20529-60205 Compiègne Cedex, France b Centre d'Analyses et de Recherche, UR TVA, Faculté des Sciences, Université Saint-Joseph, B.P. 11-514 Riad El Solh, Beirut 1107 2050, Lebanon abstract article info Article history: Received 7 February 2014 Received in revised form 2 April 2014 Accepted 13 April 2014 Available online xxxx Keywords: Polyphenols Proteins Ultrasounds High-voltage electrical discharges Pulsed electric fields This work examined the potential of valorization of vine shoots through their polyphenol and protein contents. However the choice of the experimental conditions targeted polyphenol extraction at the expense of proteins for further simplification of the purification process. The intensification of polyphenol and protein extraction by physical treatments (pulsed electric fields (PEF), high-voltage electrical discharges (HVED) and ultrasound (US)) was studied. A significant enhancement of polyphenol extraction was noticed with HVED, PEF and US. However, and for each treatment, the improvement of the extraction process started beyond a specific energetic threshold (HVED (10 kJ/kg), PEF (50 kJ/kg) and US (1010 kJ/kg)). HVED had the highest polyphenol and protein extraction yields with the lowest energetic prerequisite. Extracts of high polyphenol yield (34.5 mg of gallic acid equivalent (GAE) per g of dry matter (DM)) and high purity (89%) were obtained with HVED. Polyphenol and protein diffusion coefficients (m 2 /s) demonstrated HVED to better enhance the extraction process of those bio- molecules. Similarly, the calculation of the electrical conductivity disintegration index, Z, showed the highest tis- sue damage for HVED and a rising cellular damage with the increased energetic requirement of each treatment. © 2014 Elsevier Ltd. All rights reserved. Introduction Vine shoots are agricultural byproducts conventionally used as a heating source or left on the ground to rot (Luque-Rodríguez, Pérez- Juan, & Luque de Castro, 2006). The valorization of vine shoots has been focused over the production of ethanol and paper pulp (Delgado-Torre, Ferreiro-Vera, Priego-Capote, Pérez-Juan, & Luque de Castro, 2012), however using this raw material as a source of polyphe- nols would increase its economic value (Luque-Rodríguez et al., 2006). Vine shoots were shown to be an important source of polyphenols and proteins, which contents varied depending on the cultivars and ex- perimental conditions. Solid–liquid extraction gave polyphenol yield varying from 25.36 ± 1.62 (Atasarısı variety) to 36.56 ± 2.67 mg GAE/g (Trakya İlkeren variety), while protein content changed from 12.09 g/100 g to 28.13 g/100 g (Çetin, Altinöz, Tarçan, & Göktürk Baydar, 2011). Superheated ethanol–water extraction of polyphenols from vine shoots gave yields from 17 to 41 mg of GAE/g depending on the experimental parameters (Luque-Rodríguez et al., 2006). Whether forming part of lignin or found as extractives (non-structural compo- nents) (Romero & Sánchez, 2005), polyphenols are extracted from vine shoots and contribute in obtaining high-added value products in nutraceutical, pharmacological and oenological industries (Delgado- Torre et al., 2012). Moreover, grape canes can be considered as dietary supplements, since they are protein rich plant materials (Çetin et al., 2011). During the last decencies non-conventional environmentally friendly methods have been developed to enhance the extraction pro- cesses, giving higher yields and better extract quality than classic ex- traction methods (Soxhlet, etc.). Non-conventional physical methods can decrease chemical use, and reduce operational time (Azmir et al., 2013). Recently, pulsed electric fields (PEF) and high-voltage electrical discharges (HVED) have been tested for polyphenol extraction from various byproducts (Boussetta, Grimi, Lebovka, & Vorobiev, 2013; Boussetta, Lanoisellé, Bedel-Cloutour, & Vorobiev, 2009; Boussetta, Lebovka, et al., 2009; Corrales, Toepfl, Butz, Knorr, & Tauscher, 2008; Grimi, Lebovka, Vorobiev, & Vaxelaire, 2009; Grimi, Mamouni, Lebovka, Vorobiev, & Vaxelaire, 2011; Puértolas, López, Condón, Álvarez, & Raso, 2010). PEF induce the membrane electroporation phenomenon. When subjected to an external electric field, the electrical potential difference across the cell membrane increases. If the induced electrical potential exceeds some threshold value (1–2 V for most plant tissues), the cell membrane loses its semipermeability leading to pore creation named electroporation (Barbosa-Cánovas, Góngora-Nieto, Pothakamury, & Swanson, 1999). HVED induce the electrical breakdown in water (Boussetta, Lesaint, & Vorobiev, 2013). Formed as a result of local heating, or already present in water, air bubbles are implicated in this Food Research International xxx (2014) xxx–xxx ⁎ Corresponding author at: Université de Technologie de Compiègne, Unité Transformations Intégrées de la Matière Renouvelable, Centre de Recherches de Royallieu, B.P. 20529-60205 Compiègne Cedex, France. Fax: +33 344971591. E-mail address: nadia.boussetta@utc.fr (N. Boussetta). FRIN-05210; No of Pages 7 http://dx.doi.org/10.1016/j.foodres.2014.04.024 0963-9969/© 2014 Elsevier Ltd. All rights reserved. Contents lists available at ScienceDirect Food Research International journal homepage: www.elsevier.com/locate/foodres Please cite this article as: Rajha, H.N., et al., A comparative study of physical pretreatments for the extraction of polyphenols and proteins from vine shoots, Food Research International (2014), http://dx.doi.org/10.1016/j.foodres.2014.04.024