Antioxidant polymers for food packaging

Over the last decade there is a growing interest in the development of packaging materials and strategy aimed to preserve food quality over storage time. One of the main problems is the oxidative reaction involving food components, such as lipids, proteins, and polysaccharides. Among them, lipids play a prominent role in determining food quality because they represent the main targets of oxidative reactions, the major problem in both natural and processed food products. Lipid oxidation can cause serious loss in food quality because this wide class of chemical species effects nutritional (due to the presence of essential fatty acids and fat soluble vitamins), taste, satiety, and health properties of foodstuffs (Elias et al., 2008; Ozdemir and Floros, 2004; Tian et al., 2013). Oxidation of food components can be controlled by preventing the formation of hydroperoxides and free radicals, or by scavenging the free radicals generated in the food system. Thus, in order to inhibit oxidative reactions and preserve food quality and nutrition value, a variety of synthetic and natural antioxidants have been added to packaging materials with the development of the so-called antioxidant active packaging. By imparting specific, intentional functionality to the packaging system, active packaging is an extension of conventional packaging concept, which provides only an inert barrier to external conditions (Sacharow, 2006). Active packaging is a valuable strategy to extend shelf life, impart postpackage processing, or improve food safety and quality (Brody et al., 2008; Coma, 2008; Silvestre et al., 2011; Yam et al., 2005). In terms of mechanism of action, it allows that the antioxidant molecules can be classified as primary or secondary, even if some active agents possess both mechanisms (Chaiyasit et al., 2007). It should be considered that the use of antioxidants in active packaging may cause adverse effects on food-quality attributes, such as taste, color, and viscosity changes (Arrua et al., 2010), thus specific technologies should be pointed out for the preparation of antioxidant packaging materials. These technologies should be developed by considering either the intended product application or specific mechanism of activity of the selected antioxidant. According to literature, antioxidant agents can be applied into the packaging systems in different forms, mainly including independent sachet packages, adhesive-bonded labels, physical adsorption/coating on packaging material surface, being incorporated into packaging polymer matrix, multilayer films, and covalent immobilization onto the food contact packaging surface (Amorati et al., 2013; Gómez-Estaca et al., 2014; Silva-Weiss et al., 2013). Polymers constitute one of the main classes of compounds within the global chemical market because these materials, both of natural and synthetic origin, are practically indispensable for the everyday life in the modern society (Kobayashi and Makino, 2009). This chapter focuses on the recent development of antioxidant packaging by investigating the role of polymer/antioxidant supramolecular complexes, including both the noncovalent incorporation and the covalent conjugation of antioxidant species to polymeric backbone. Finally, the further improvement related to the introduction of suitable inorganic materials for the development of nanocomposites is also presented and discussed.