Influence of PA6 nanocomposite films on the stability of vacuum-aged beef loins during storage in modified atmospheres P.A. Picouet a, ⁎, A. Fernandez b , C.E. Realini a , E. Lloret a a Departament de Tecnologia dels Aliments, Institut de Recerca i Tecnologia Agroalimentàries (IRTA), Monells, Girona, Spain b Instituto de Agroquímica y Tecnología de Alimentos, Consejo Superior de Investigaciones Científicas (CSIC), Avda. Agustín Escardino 7, 46980 Paterna, Spain abstract article info Article history: Received 30 January 2013 Received in revised form 3 July 2013 Accepted 16 July 2013 Keywords: Nanocomposites PA6 Multilayer Organoclays Beef ageing MAP packaging A masterbatch of polyamide 6 (PA6) containing dispersed nanoclays, was used to fabricate a novel multilayer film for vacuum packed meat. Performance of the nanocomposite was compared to a control PA6 multilayer and a high barrier commercial film. Addition of nanoclays improved oxygen barrier properties, UV-blocking ca- pability and stiffness. Beef loins were vacuum-aged using the three films for 0 7, 14 and 21 days at 2 °C. After each ageing time, beef steaks were packaged in commercial trays and high oxygen atmosphere and stored at 4 °C for 9 days. Beef quality parameters and gas content were studied during display time in MAP (1, 3, 6 and 9 d). Beef quality parameters were not influenced by the packaging materials used during ageing and the performance of nanocomposites was comparable to high barrier films. Ageing had a positive impact on the stabilization of red- ness up to day 6 in MAP. Thereafter, oxymyoglobin content and oxidation levels were negatively influenced by ageing. © 2013 Elsevier Ltd. All rights reserved. 1. Introduction Highly innovative hybrid organic–inorganic nanomaterials are being implemented as fillers for polymer composites. The food packaging in- dustry has focused attention on nanoplatelets like clays and silicates (De Azeredo, 2009). Due to the size in the nanometer range, those ma- terials present specific properties, such as high surface areas and high aspect ratios (ratio of length vs. breadth), that can modify the physical and mechanical properties of the polymer matrix. Potential applications of such materials are the reinforcement of mechanical and barrier prop- erties in food packaging materials (Adame & Beall, 2009; Rhim, Hong, & Ha, 2009), the controlled release of bioactive molecules, the incorpora- tion of biocide surfaces, or as nanosensors (Duncan, 2011; Llorens, Lloret, Picouet, Trbojevich, & Fernandez, 2012). In general, the dispersion of nano-sized fillers into polymers would enhance the barrier properties of packaging polymers via an increase in tortuosity. They can be incorporated directly inside the packag- ing material as nanocomposites or they can be applied on a surface (nano-coatings) in multilayers (Bradley, Castle, & Chaudhry, 2011). Suitable polymers are food grade polymers, such as polyamides, and the organo-modified clays are often prepared from natural clays, by ex- changing the sodium cations with organic surfactants (Picard, Gérard, & Espuche, 2008). Regarding polyamide 6 nanocomposites, the addition of montmorillonite produced an increase in viscosity during elongation (Baldi, Franceschini, Bignotti, Tieghi, & Riccò, 2009), and a more shear- thinning behavior (Tung, Gupta, Simon, Edward, & Bhattacharya, 2005). However, the presence of agglomerates acted as stress concen- trators leading to an earlier initiation of the crack during tension. Picard et al. (2008) showed an increase in barrier properties to helium, dihydrogen, dioxygen and water, and reported a “tortuous pathway” mechanism that was able to improve the barrier properties indepen- dently of the amount of clay up to 18 wt.%. By compression molding, intercalated or exfoliated structures have been reported, the exfo- liated structures being more effective to decrease the permeability (Alexandre et al., 2001). Also Beatrice, Branciforti, Alves, and Bretas (2010) and Fasihi and Abolghasemi (2011) reported enhanced barrier properties to water vapor and oxygen in exfoliated montmorillonite PA6 nanocomposites. The popularity of the nano-clay fillers for food ap- plications relies also in the low price of the raw material, high stability and benignity. Thus, it might be expected that new nanocomposite ma- terials should be feasible to design new efficient low cost multilayer films with applicability in the meat sector. Tenderness is one of the major criteria that contribute most to eating satisfaction of Europeans (Glitsch, 2000; Realini et al., 2009; Troy & Kerry, 2010) and consumers are willing to pay more for tender beef (Chambaz, Scheeder, Kreuzer, & Dufey, 2003; Miller, Carr, Ramsey, Crockett, & Hoover, 2001; Wheeler & Koohmaraie, 1994). Unfortunately, tenderness is also a highly variable characteristic and its inconsistency is a common cause of consumer dissatisfaction (Destefanis, Brugiapaglia, Barge, & Dal Molin, 2008), becoming a priority for the meat industry (Koohmaraie, 1996). Ageing of beef post-mortem is a well known Meat Science 96 (2014) 574–580 ⁎ Corresponding author: Tel.: +34 972630052ext1450; fax: +34 972630373. E-mail address: pierre.picouet@irta.es (P.A. Picouet). 0309-1740/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.meatsci.2013.07.020 Contents lists available at ScienceDirect Meat Science journal homepage: www.elsevier.com/locate/meatsci