Starch-based antimicrobial films functionalized by pomegranate peel Amjad Ali a , Ying Chen a , Hongsheng Liu a,b, ⁎, Long Yu a,b, ⁎, Zulqarnain Baloch c , Saud Khalid a , Jian Zhu a , Ling Chen a a School of Food Science and Engineering, South China University of Technology, Guangzhou 510640, China b Sino-Singapore International Joint Research Institute, Guangzhou Knowledge City, Guangzhou 510663, China c College of Veterinary Medicine, South China Agricultural University, Guangzhou 510642, China abstract article info Article history: Received 18 June 2018 Received in revised form 9 September 2018 Accepted 11 September 2018 Available online xxxx In this work, pomegranate peel (PGP) as an antimicrobial agent as well as a reinforcing agent was utilized in de- veloping starch-based films. Hydroxypropyl high-amylose starch plasticized by water and glycerol was used in this work. The microstructure and performance of films were investigated using scanning electron microscope (SEM), optical microscope (OM), X-ray diffraction (XRD), dynamic mechanical analyzer, tensile testing, drop im- pact testing and disc diffusion test. Results clearly demonstrated that PGP inhibited the growth of both gram- positive (S. aureus) and gram-negative (Salmonella) bacteria. Meanwhile, PGP also increased Young's modulus, tensile strength and stiffness of the starch-based films. Both OM and SEM observations indicated reasonably good compatibility between starch and PGP particles. The XRD results indicated that PGP retained its semi- crystalline structure in the film, which can be used to explain the mechanism of mechanical reinforcement. Since all the components are food ingredients, so it is expected that the developed material can be used as an ed- ible film and food grade packaging material. © 2018 Elsevier B.V. All rights reserved. Keywords: Starch Film Pomegranate peel Antimicrobial Food package 1. Introduction Various antimicrobial food packaging systems have been developed using different natural polymeric matrices including protein, chitosan, gelatin, pectin and starch [1–4]. Among these natural polymers, starch is the most promising biodegradable material used as matrix due to its low cost, wide availability and compostability without forming any toxic residue. Starch based films have been used widely in food and non-food application [2,5]. Starch-based antimicrobial films are also gaining popularity in market as it protects the food commodity from mi- crobial contamination [6], act as barrier for gases and volatile com- pounds and maintain the quality of food products for distant marketing [7]. In order to develop starch-based antimicrobial materials, various an- timicrobial chemicals have been evaluated including silver, copper [8,9], zinc oxide and zinc rod [10]. However, these chemicals are not applica- ble on commercial scale due to their toxicological effects on human health and environmental issues. For example, silver nanoparticles are restricted for commercial use in EU [11]. On the other hand, the demand for safe and ready-to-serve food prepared by generally recognized as safe (GRAS) preservatives to control microbial contamination is increas- ing [12]. Application of antimicrobial agents from natural sources is gaining more and more popularity in preserving the food from micro- bial attack and in developing anti-microbial food packaging materials [8,13]. Pomegranate (Punica granatum L.) fruit peel is one of the most valu- able by-product of the food industry [14]. It is a rich source of bioactive compounds [15,16], possesses unique biological activities, inhibits mi- crobial growth and reduces the risk of cancer and cardiovascular disor- ders [17,18]. During the processing of pomegranate juice, 78% of peel is collected as a residue [19]. The pomegranate fruit peel contains phenolic compounds including ellagic acid, ellagitannins, lignins, catechin, rutin, punicalagin and epicatechin [15,20–22]. The peel is mainly comprised of cellulose (16–22 g), lignin (20–41 g), pectin (14–23%) and some pro- teins [23,24]. Actually, all parts of pomegranate (fruit, peel, aerial, leaf, and roots) possess antibacterial, anticancer, and antioxidant activity, as widely reported [18,21,22,25–31]. It has been shown that pomegranate peel extract demonstrate pos- itive results against microbes [32] by enhancing the shelf-life of chicken and other meat products [21,22,32]. However, there is no report about the incorporation of pomegranate peel as filler in starch based films to develop antimicrobial materials. It is well known that the poor mechan- ical properties and high water affinity of starch based films limit its many applications [34,35]. In order to improve the mechanical proper- ties of starch based films, it has been blended with various mineral or natural fillers [36–38]. Reinforcement of starch based films with natural fillers exhibit extraordinary advantage of biocompatibility and biode- gradability for packaging, agricultural and pharmaceutical applications International Journal of Biological Macromolecules xxx (xxxx) xxx–xxx ⁎ Corresponding authors at: School of Food Science and Engineering, South China University of Technology, Guangzhou 510640, China. E-mail addresses: liuhongsheng@scut.edu.cn (H. Liu), felyu@scut.edu.cn (L. Yu). BIOMAC-10503; No of Pages 7 https://doi.org/10.1016/j.ijbiomac.2018.09.068 0141-8130/© 2018 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect International Journal of Biological Macromolecules journal homepage: http://www.elsevier.com/locate/ijbiomac Please cite this article as: A. Ali, et al., Starch-based antimicrobial films functionalized by pomegranate peel, (2018), https://doi.org/10.1016/j. ijbiomac.2018.09.068