Characterization of edible gum cordia film: Effects of plasticizers Muhammad Abdul Haq * , Abid Hasnain, Mahmood Azam Department of Food Science & Technology, University of Karachi, Karachi 75270, Pakistan article info Article history: Received 2 March 2013 Received in revised form 19 September 2013 Accepted 26 September 2013 Keywords: Gum cordia Plasticizer Edible film Tensile strength abstract Gum Cordia based edible films were fabricated as a function of plasticizer type and concentration and their thermal, mechanical and gas permeation were investigated. Solution casting method was adopted for film fabrication. Glycerol, sorbitol, PEG 200 and PEG 400 in the range of 0.1e0.3 g g 1 dry polymer weight basis were used as plasticizer. Film properties were found to be dependent on the plasticizer type and concentration. Fourier transform infrared (FTIR) spectroscopy revealed some interaction between plasticizers and the polymer. Differential scanning calorimetry (DSC) supported that plasticizers were miscible with the polymer. The glass transition temperature was found to be between 66 and 11  C. Mechanically, gum Cordia films were found to have good tensile strength (>10 MPa) and elongation at break (>10%). The most pronounced change in tensile property was exerted by glycerol followed by sorbitol, PEG 200 and PEG 400 respectively. Water vapor permeability was found to be in the range 0.91 e5.5  10 10 gm 1 s 1 Pa 1 . Oxygen permeability was found to be between 0.16 and 5.31  10 15 gm 1 s 1 Pa 1 . Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Edible films and coatings are environmentally friendly, biode- gradable and low cost packaging materials, which are prepared from biopolymers. The existing materials have limitations in terms of cost, availability and functional properties (Vieira, da Silva, dos Santos, & Beppu, 2011). Therefore, new biological resources for this purpose are being continuously explored (Azam, Haq, & Hasnain, 2013). Cordia myxa is a small tree of plant Family Bor- aginaceae, which grows nearly all over the Indo-Pak subcontinent but has very few uses (Haq, Alam, & Hasnain, 2013). The ripe fruits contain gum composed of an anionic polysaccharide which is covalently bound with protein (Benhura & Chidewe, 2011). The polysaccharide is an arabinoglucan with the backbone of (1 / 6)- linked D-glucopyranosyl and (1 / 2)-linked L-arabinofuranosyl residues (Basu, Ghosal, & Thakur, 1984). Its inherent adhesion property suggests that it is an ideal candidate for biodegradable films and coatings. Authors have already published some of the successful applications of gum cordia as a coating material on nuts to retard oxidative rancidity (Haq et al., 2013; Haq & Hasnain, 2013a, b). Native biopolymers usually form brittle films due to extensive interactions between polymer chains through hydrogen bonding, electrostatic forces, hydrophobic bonding and cross link- ing. Plasticizers are small molecular mass compounds which are believed to reduce these interactions and thus make the resulting film soft and flexible (Bergo & Sobral, 2007). The ability of a plas- ticizer to form such bonds depends on their molecular configura- tion, no of free hydroxyl groups and the configuration of the biopolymer i.e. compatibility of the plasticizer with polymer. Therefore, for every biopolymer the type and optimum concen- tration of plasticizer has to be determined in order to use it suc- cessfully in various conditions. FTIR has been reported to study the interaction of plasticizer with polymer (Bergo & Sobral, 2007; Velazquez, Herrera-Gómez, & Martín-Polo, 2003; Zhang & Han, 2006). For example, Bergo and Sobral (2007) studied the effects of glycerol on gelatin film using FTIR and found that increasing the glycerol content shifts the peak at 1034 cm 1 to lower wave numbers due to interaction between the plasticizer and the polymer. This study was designed to characterize the gum cordia film prepared by using different types of plasticizers at various concentrations. 2. Materials and methods The fruits of C. myxa were collected from Karachi region of Pakistan. The gum was extracted as described previously by our group (Haq et al., 2013). In entire study, analytical reagent grade * Corresponding author. Tel.: þ92 213 992613006x2452, þ92 213 992613006x3292; fax: þ92 213 99261330. E-mail addresses: abdul.haq@uok.edu.pk, abdul.haq20pk@gmail.com (M.A. Haq). Contents lists available at ScienceDirect LWT - Food Science and Technology journal homepage: www.elsevier.com/locate/lwt 0023-6438/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.lwt.2013.09.027 LWT - Food Science and Technology 55 (2014) 163e169