Physicochemical properties of gelatin/silver nanoparticle antimicrobial composite films Paulraj Kanmani, Jong-Whan Rhim ⇑ Department of Food Engineering and Bionanocomposite Research Institute, Mokpo National University, 61 Dorimri, Chyungkyemyon, Muangun 534-729, Jeonnam, Republic of Korea article info Article history: Received 28 May 2013 Received in revised form 21 August 2013 Accepted 9 October 2013 Available online 18 October 2013 Keywords: Gelatin Silver nanoparticles Nanocomposites Antibacterial Food packaging abstract Active nanocomposite films were prepared by blending aqueous solutions of gelatin with different concentrations of silver nanoparticles (AgNPs) using a solvent casting method. Formation of silver nanoparticles in the solution and films was confirmed with the surface plasmon resonance (SPR) band at 400–450 nm, measured by UV–vis absorption spectroscopy. The incorporation of AgNPs slightly affected the physical and mechanical properties of the films. Increase in the concentration of AgNPs resulted in a substantial decrease in water vapour permeability (WVP) and tensile strength (TS) of the gelatin films. Energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) analysis confirmed the presence of elemental silver and crystalline structure of the AgNPs in the gelatin film. Microscopic surface structure and thermal properties of the films were also examined by FE-SEM and thermogravi- metric analysis. Gelatin/AgNPs nanocomposite films exhibited strong antibacterial activity against food-borne pathogens. Gelatin/AgNPs nanocomposite films are expected to have high potential as an active food packaging system to maintain food safety and to extend the shelf-life of packaged foods. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Microbial contamination can reduce the shelf life of food, in- crease the risks of various food-borne infections, and cause serious illness (Devlieghere, Vermeiren, & Debevere, 2004). Traditionally, various physical and chemical preservation methods have been used in the food industry to reduce the spoilage of food, to maintain food quality, and to extend shelf life. However, recent in- creased consumer demands for minimally processed and ready-to- eat fresh foods have motivated researchers to develop alternative new technologies for securing food safety and providing healthy food. Recently, novel active food packaging systems have been introduced to meet consumer demands and to extend the shelf life of food. Antimicrobial packaging (AMP) is one of the promising ac- tive food packaging technologies which is often achieved by incor- poration or immobilization of potent antimicrobial agents into the packaging system. Various organic and inorganic materials have been used as antimicrobial agents for packaging. However, less heat-stable organic materials could limit their wide use in food packaging systems. By contrast, inorganic nano-size metallic parti- cles, such as gold, silver, zinc, and copper, are not only more stable but also possesses a high surface to volume ratio with increased surface reactivity (Llorens, Lloret, Picouet, Trbojevich, & Fernandez, 2012). Therefore, metallic nanoparticles (NPs) have been widely used industrially for the past two decades. Among the metal NPs, silver nanoparticles (AgNPs) have attracted especial attention in the food packing sector because of their remarkable and broad spectrum of antimicrobial effect against food-borne pathogens. The incorporation of AgNPs into the food packaging system could effectively inhibit the growth of pathogenic microorganisms (Llorens et al., 2012). Various physical and chemical methods have been utilized for the production of sil- ver nanoparticles (Bankura et al., 2012). Generally, chemical meth- ods have been widely used for the preparation of nano-scale metallic particles. However, some toxicological effects have been reported, after the use of hazardous chemicals as reducing agents. Thus, various alternative methods have been developed to synthe- size AgNPs, using eco-friendly, biocompatible, and safe biological resources. Biological systems, such as bacteria, fungi, yeasts, plant extracts, actinomycetes, and certain biological components, have also been listed as safe, to produce AgNPs at extracellular and intercellular level (Bankura et al., 2012). Currently, there is a grow- ing interest in the production of active AgNPs with potent antimi- crobial effects, using polysaccharides such as starch (Mohanty et al., 2012), chitosan (Vimala et al, 2010), agar (Rhim, Wang, & Hong, 2013), pullulan, dextran (Bankura et al., 2012), guar gum (Pandey, Goswami, & Nanda, 2012), and alginate (Seo et al., 2012). However, there is no report available for the production of AgNPs using protein such as gelatin as reducing and stabilizing agents. 0308-8146/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.foodchem.2013.10.047 ⇑ Corresponding author. Tel.: +82 61 450 2423; fax: +82 61 454 1521. E-mail addresses: jwrhim@mokpo.ac.kr, jwrhim@hanmail.net (J.-W. Rhim). Food Chemistry 148 (2014) 162–169 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem