Contents lists available at ScienceDirect Progress in Organic Coatings journal homepage: www.elsevier.com/locate/porgcoat A pyrogallol-coated modified LDPE film as an oxygen scavenging film for active packaging materials Kirtiraj K. Gaikwad, Suman Singh, Youn Suk Lee ⁎ Department of Packaging, Yonsei University, 1 Yonseidae-gil, Wonju, Gangwon-do, 26493, South Korea ARTICLE INFO Keywords: Pyrogallol Oxygen scavenger Polyurethane Film coating Active packaging ABSTRACT Oxygen scavenging films were prepared with 1, 3, 5, 10, and 20% pyrogallol coated onto a modified LDPE film. The color, mechanical, barrier, and surface properties of the LDPE/PG oxygen scavenging films were compared to those of a pure LDPE film. The results demonstrate that pyrogallol was well coated onto the surface of the modified LDPE film. The LDPE/PG films had a slightly rough film surface, which results in higher water and oxygen permeabilities as well as lower TS due to the addition and agglomerations of sodium carbonate and pyrogallol. The pyrogallol coating also caused color alterations of the LDPE/PG film. In addition, the oxygen scavenging properties of the LDPE/PG films were evaluated at different relative humidities (RH) and tem- peratures. The oxygen content (%) in the headspace of the absorption cell containing the LDPE/PG 20% film, which was initially 20.9%, decreased to 9.42% after 8 days at 23 °C. The LDPE/PG 20% film showed an effective oxygen scavenging capacity of 0.443 mL/cm 2 at 23 °C. Water was used as an activator to initiate the oxygen scavenging reaction. 1. Introduction Oxygen is a main cause of food spoilage. The amount of oxygen in the headspace of a package is responsible for oxidation in food pro- ducts, resulting in changes of the flavor, color, texture, a loss of nu- tritive qualities, and hence, a shorter food shelf life [1–4]. To prevent such undesirable effects and to achieve a long food shelf life, the re- moval of oxygen and lowering the oxygen concentration from the package is a key target. Technologies including vacuum packaging (removal of gases), modified atmosphere packaging (MAP), and oxygen absorbing techniques have been used to reduce the concentration of oxygen from packages over the past two decades [5–7]. Among these technologies, vacuum technology and MAP are able to remove oxygen down to 1% in the package headspace during storage while on the other hand, an oxygen scavenger can reduce the oxygen concentration in a package to 0.01% [8]. An oxygen scavenger is able to absorb oxygen which diffuses through the wall of package from the outside environ- ment into the package throughout the storage period and it also reduces the oxygen which is present inside the package before the sealing process [9]. Oxygen scavenging sachets, which contain iron (Fe)-based powder, are the most commonly used commercially established tech- nology used to remove oxygen. However, oxygen scavenging sachets have several limitations for food packaging use. For example, there is the potential risk of accidental consumption by children and babies, packages containing oxygen scavenging sachets cannot be used in mi- crowave ovens, and they create issues for metal detectors in the food production line. In addition, in the case of liquid food products such as juices, the use of oxygen scavenging sachets is not possible [10]. The use of organic-based oxygen scavenging materials has increased over the past few years in research studies involving organic-based products for active packaging use [11]. There are various ways to in- corporate oxygen scavengers into polymers. Nevertheless, the choices for organic compounds are generally limited due to their low thermal properties in polymer processing such as polymer extrusion and injec- tion molding processes [12,13]. Due to these reasons, the coating of oxygen scavenging compounds on the surface of a packaging material is a solution to overcome this issue. For these reasons, researchers from the field of functional packaging have recently focused on non-metallic organic compounds as the main material for the development of oxygen scavengers [1]. Recently, sev- eral investigators developed oxygen scavenging films via a coating method [14–16]. These functional oxygen absorbing plastic films effi- ciently absorbed oxygen, which is important in food packaging. Pyrogallol (C 6 H 6 O 3 ) (PG) is a natural phenolic compound found in different crops and fruits such as Litchi and Indian gooseberries [17]. It has been confirmed that some portion of pyrogallol is an active flavo- noid constituent and presents a high oxygen absorbing activity since pyrogallol effectively reacts with oxygen [7]. It also has antimicrobial http://dx.doi.org/10.1016/j.porgcoat.2017.05.016 Received 30 December 2016; Received in revised form 21 April 2017; Accepted 21 May 2017 ⁎ Corresponding author. E-mail address: leeyouns@yonsei.ac.kr (Y.S. Lee). Progress in Organic Coatings 111 (2017) 186–195 0300-9440/ © 2017 Elsevier B.V. All rights reserved. MARK