Development of Palladium-based Oxygen Scavenger: Optimization of Substrate and Palladium Layer Thickness

Abstract

Oxygen scavenging films based on vacuum deposited palladium layers were developed to remove residual oxygen remaining in food packages after modified atmosphere packaging. Palladium (Pd) was coated on to a range of packaging films and in different thicknesses using magnetron sputtering technology. To improve the substrate surface, an additional silicon oxide (SiO x ) layer was also applied to the films before Pd deposition. To determine the oxygen scavenging activity, the scavenger films were placed into an airtight cell, which was flushed with a gas mixture containing 2 vol.% oxygen and 5 vol.% hydrogen. The results showed that the oxygen scavenging rate was strongly dependent on the coating substrate as well as on the Pd deposition thickness. Packaging films such as polyethylene terephthalate, aluminium oxide-coated polyethylene terephthalate, oriented polypropylene and polylactic acid were found to be the most suitable substrates for Pd-based oxygen scavengers. Moreover, it was demonstrated that the intermediate SiO x layer between the substrate and the Pd layer led to a substantial increase in the oxygen scavenging activity rate (up to 33-fold) for all applied packaging films. Additionally, it was shown that the optimal Pd layer thickness for the investigated oxygen scavenging films lies between 0.7 and 3.4 nm. The resulting scavenger films have the potential to scavenge residual headspace oxygen of sensitive foods within a matter of minutes leading to shelf life extension and overall quality improvements.

Transformation of food packaging from passive to innovative via nanotechnology: concepts and critiques

“…Nanocomposites are composites or hybrid materials that comprise a dispersion of nanometer size particles in a polymer matrix (Tang et al 2011). Most used nanomaterials for this purpose are carbon nanotubes (CNTs), clay platelets (montmorollites/nanoclays) and bionanocomposites (de Azeredo 2009;Yildirim et al 2015).…”

“…2). The prominent forms of active food packaging are based on (i) antimicrobial agents (Gemili et al 2010;Wen et al 2016), (ii) scavenging systems for oxygen using ferrous oxide, zeolite, palladium, cobalt, photosensitive dyes, glucose oxidase, activated carbon, ethanol oxidase, ascorbic acid, ascorbate salts or catechol (Joven et al 2015;Mahieu et al 2015) and (iii) moisture absorbers using sachets, pads, sheets or blankets and therapeutic probiotics food (Dobrucka and Cierpiszewski 2014;Mahajan et al 2008;Yildirim et al 2015).…”

“…In addition, ascorbic and iron powders or copper chloride as a catalyst for extruded oxygen scavenging thermoplastic starch films exhibited reduction in oxygen transmission rate of films from 20.9 to 1 % for 15 days at 80 % RH (Mahieu et al 2015). Similarly, the oxygen scavenging polyethylene terephthalate (PET) films, PET-aluminum oxide coatings, polylactic acid films and oriented polypropylene (o-PP) films were deposited with palladium layers through vacuum deposition on silicon oxide (SiOv) layer for modified atmosphere packaging (Yildirim et al 2015). The coating of the films significantly reduced the oxygen transmission rate through the film layers up to 33-fold.…”

“…The superhydrophobicity of surfaces (angle [150°with water) prevent the wetting properties of substrate due to the reduced contact point and low surface tension of water Ye et al 2015). Common materials in construction of bioinspired self-cleaning packages include titania and silicon nanoparticles, CNTs and graphite (Liu et al 2015a, c;Wu et al 2015a;Yildirim et al 2015). The selfcleaning copolymer brushes of N-isopropylacrylamide (NIPAAm) and poly(ethylene glycol) methacrylate (PEGMA) embedded on polypropylene (PP) surface increased oil contact angle higher than 141°and lowered the oil adhesive forces below 20 lN (Ye et al 2015).…”

“…In this case, active food packaging can be easily integrated with smart and intelligent packaging features, which presents the multipurpose packaging systems. For example metallic, metallic oxides and their nanoparticles can be diversely applied in antimicrobial applications, barrier functions, detecting systems (Imran et al 2010;Yildirim et al 2015), photoreactive substances (Rashidi and Khosravi-Darani 2011) and self-cleaning materials when coated on surface of various substrates (Liu et al 2015a, b;Wu et al 2015a). These include nanomaterials from iron oxides, gold, alumina, silver, silica, zinc oxide, CNTs, graphites (Ranjan et al 2014) and titania (TiO 2 ).…”