Characterization, release and antioxidant activity of curcumin-loaded amaranth-pullulan electrospun fibers Adriana Blanco-Padilla a , Amparo L  opez-Rubio b , Guadalupe Loarca-Pi ~ na a , Laura G. G  omez-Mascaraque b , Sandra Mendoza a, * a Dept. de Investigaci on y Posgrado en Alimentos, Facultad de Química, Universidad Aut onoma de Quer etaro, 76010, Quer etaro, Mexico b Novel Materials and Nanotechnology Group, IATA-CSIC, Avda. Agustin Escardino 7, Paterna, 46980, Valencia, Spain article info Article history: Received 19 November 2014 Received in revised form 25 February 2015 Accepted 18 March 2015 Available online 11 April 2015 Keywords: Electrospinning Amaranth protein Pullulan Encapsulation Curcumin abstract In this work, ultrathin electrospun fibers from two different blends of amaranth protein isolate (API) and the carbohydrate polymer pullulan (Pul) were loaded with two different concentrations of curcumin (0.05% y 0.075%). The loaded electrospun fibers were physicochemically characterized and the curcumin release profile as well as its antioxidant capacity under in vitro digestion conditions was evaluated. Round, uniform and homogenous fibers with diameters of around 224.5e248.6 nm were obtained for loaded API:Pul 50:50 fibers. The encapsulation efficiencies of curcumin varied between ~73% and ~93% for both loadings and fiber compositions. Moreover, a controlled and sustained released of curcumin was observed both in buffer solution (pH ¼ 7.4) and during an in-vitro digestion process. The antioxidant activity of curcumin entrapped within the ultrathin fibers was maintained after the in vitro digestion process and it was superior in comparison with the non-encapsulated bioactive compound. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Curcumin is a pleiotropic molecule (Fig. 1) that has been used as a remedy in traditional medicine in China and India (Hatcher, Planalp, Chob, Tortia, & Tortic, 2008). Several in vitro and in vivo studies have reported that curcumin has beneficial properties such as anti-inflammatory (Anand et al., 2008), antioxidant (Menon & Sudheer, 2007), and chemopreventive (Park, Ruhul, Georgia, & Shin, 2013). However, its poor water solubility and chemical instability reduce its bioavailability and, thus, its biological effect (Strimpakos & Sharma, 2008). Encapsulation represents an avail- able and efficient approach to circumvent this problem. Therefore, curcumin has been encapsulated in nanoparticles (Bisht et al., 2007; Dadhaniya et al., 2011; Kumar, Kasoju, & Bora, 2010), superparamagnetic silica reservoirs (Chin et al., 2009) and ultrathin fibers (Fu et al., 2014). An ultrathin fiber is a one-dimensional flexible nano-element that can be processed by electrospinning (Ramakrishna, Fujihara, Teo, Lim, & Ma, 2005) and it has several advantages over other encapsulation systems such as high surface area per unit volume, high encapsulation efficiency and controlled release characteristics (Hu et al., 2014). Biopolymers can offer renewable nature, biodegradability, biocompatibility (Schiffman & Schauer, 2008), and they possess the necessary characteristics as specific visco-elastic properties, electric conductivities and surface tension values to produce electrospun fibers (Agarwal, Greiner, & Wendorff, 2009). Some types of proteins have been electrospun to obtain nanofibers such as casein (Xie & Hsieh, 2003), soy protein (Har-el, Gerstenhaber, Brodsky, Huneke, & Lelkes, 2014; Vega-Lugo & Lim, 2009), and more recently zein (Oliveira et al., 2014). Amaranth (Amaranthus hypochondriacus) is a pseudocereal with high protein content (17%) and amino acid composition close to the optimum amino acid balance required by human nutrition (Schnetzler & Breen, 1994). Amaranth protein contains a low pro- portion of prolamins which makes it a safe ingredient for people with celiac disease and recent studies have shown that amaranth peptides displayed antihypertensive and anti-inflammatory activ- ity (Gorinstein et al., 2002; Orsini, Galleano, A~ n on, & Tironi, 2015; Silva et al., 2008). In our group, the ability of an amaranth protein isolate (API) combined with pullulan (Pul), a spinnable carbohy- drate polymer (Fig. 1), to generate electrospun microstructures was demonstrated (Aceituno-Medina, Lopez-Rubio, Mendoza, & Lagaron, 2013a, 2013b). These structures can be used to encapsulate Abbreviations: API, Amaranth protein isolate; Pul, pullulan; ATR-FTIR, Attenu- ated total reflectance infrared spectroscopy. * Corresponding author. Tel.: þ52 442 192 1304; fax: þ52 442 192 1307. E-mail address: smendoza@uaq.mx (S. Mendoza). Contents lists available at ScienceDirect LWT - Food Science and Technology journal homepage: www.elsevier.com/locate/lwt http://dx.doi.org/10.1016/j.lwt.2015.03.081 0023-6438/© 2015 Elsevier Ltd. All rights reserved. LWT- Food Science and Technology 63 (2015) 1137e1144