New approaches for the effective valorization of papaya seeds: Extraction of proteins, phenolic compounds, carbohydrates, and isothiocyanates assisted by pulsed electric energy Oleksii Parniakov a,b , Elena Roselló-Soto c , Francisco J. Barba b,c , Nabil Grimi b, ⁎, Nikolai Lebovka a,b , Eugène Vorobiev b a Institute of Biocolloidal Chemistry named after F. D. Ovcharenko, NAS of Ukraine, 42, blvr., Vernadskogo, Kyiv 03142, Ukraine b Sorbonne Universités, Université de Technologie de Compiègne, Laboratoire de Transformations Intégrées de la Matière Renouvelable, EA 4297, Centre de Recherches de Royallieu, BP 20529, 60205 Compiègne Cedex, France c Universitat de València, Faculty of Pharmacy, Nutrition and Food Science Area, Avda. Vicent Andrés Estellés, s/n 46100 Burjassot, València, Spain abstract article info Article history: Received 7 December 2014 Received in revised form 15 March 2015 Accepted 23 March 2015 Available online xxxx Keywords: Papaya seeds Pulsed electric fields High voltage electrical discharges Proteins Phenolic compounds Carbohydrates Isothiocyanates The study compares the efficiency of common aqueous extraction (CE) at different pH (2.5–11) and temperatures (20–60 °C) and extraction assisted by pulsed electric energy (pulsed electric fields, PEF or high voltage electrical discharges, HVED) of nutritionally valuable and antioxidant compounds from papaya seeds. The exponential decay pulses with initial electric field strengths of ≈13.3 kV/cm and ≈40 kV/cm for PEF and HVED treatments, respectively, were used. The number of pulses n was changed within 1–2000. The impacts of temperature and pH on extraction efficiency of different components (proteins, total phenolic compounds, carbohydrates, isothiocy- anates) and antioxidant capacity were ambiguous. The highest values of nutritionally valuable and antioxidant compounds were obtained for HVED-assisted extraction. However, the application of HVED-treatment may pro- duce undesirable contaminants (chemical products of electrolysis, free reactive radicals, etc.) and extracts were unstable and cloudy. On the other hand, the application of the two-stage procedure PEF+ supplementary aque- ous extraction (+SAE) that include PEF-assisted extraction as the first step, and + SAE at 50 °C, pH = 7 during 3 h as the second step, allowed noticeable enhancement of the yields (+200%) and antioxidant capacities (+20%) even at neutral pH. This method has high prospects of industrial applications for release of valuable components from papaya seeds. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction A large amount of wastes and by-products are generated during all the food life cycle of exotic fruits, from agriculture phase, up to industri- al manufacturing and processing, retail and household (Mirabella, Castellani, & Sala, 2014). Among these, papaya is gaining popularity, now ranked third with 11.22 Mt, or 15.36% of the total tropical fruit production (Evans & Ballen, 2012). During papaya processing, a large amount of by-products, especially seeds and peels, are produced and discarded into the environment causing organic pollution (Koubala, Christiaens, Kansci, Van Loey, & Hendrickx, 2014). Traditionally, these by-products have been considered as a problem. However, it is recog- nized that papaya seeds have some beneficial properties mainly attrib- uted to their content in high-added value compounds, especially bioactive compounds such as isothiocyanates and phenolic compounds, which can be used for application in nutraceutical supplements, dietary additives, new food and pharmaceutical products (Ayala-Zavala et al., 2011). In fact, papaya seeds have been used for decades in parts of Asia and South America as vermifugal agent and they have been used in folk medicine to facilitate good menstrual flow (Adebiyi, Adaikan, & Prasad, 2003; Thomas et al., 2009). However, at this stage of development there is a lack of information about the different extraction methods that can be used for the recovery of high-added value compounds from papaya seeds. The classical treatments (grinding, heating), and the different alter- native treatments currently used in industry to make extractions easier, degrade and disrupt the tissue structure (membranes and cellular walls) in an uncontrollable way. Unfortunately, entirely disrupted tissue losses its selectivity (capacity to sieve) and becomes permeable not just for the target cell compounds, but for undesirable compounds (impurities) passing into the extract. In this line, pulsed electric field (PEF) assisted extraction seems to be rather promising. There are many successful examples of PEF applica- tion for the recovery of high-added value compounds from plant food Food Research International xxx (2015) xxx–xxx ⁎ Corresponding author at: Université de Technologie de Compiègne, Laboratoire Transformations Intégrées de la Matière Renouvelable (TIMR EA 4297), Centre de Recherche de Royallieu, B.P. 20529-60205 Compiègne Cedex, France. Tel.: +33 3 44 23 44 42. E-mail address: nabil.grimi@utc.fr (N. Grimi). FRIN-05747; No of Pages 7 http://dx.doi.org/10.1016/j.foodres.2015.03.031 0963-9969/© 2015 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: Parniakov, O., et al., Newapproaches for the effective valorization of papaya seeds: Extraction of proteins, phenolic compounds, carbohydrates, and isot..., Food Research International (2015), http://dx.doi.org/10.1016/j.foodres.2015.03.031