ABSTRACT
The use of plastic organic polymers and functional additives such as plasticizing agents or antioxidants in the packaging, manufacture, and serving of common foodstuffs such as meat, cheese, margarine, bacon, vegetables, and beverages may result in these packaging materials potentially being considered as indirect food additives (1). This phenomenon occurs because of the potential for contact and migration or transfer of polymer components from containers or packaging films to foods during processing, packaging, and storage. Plastics (i.e., polystyrene) are also extremely prevalent as food service utensils and containers both inside and outside the home (2,3). Polymer additives can fall into two functional categories: those that modify the physical properties of polymers, namely plasticizers, lubricants, and coloring agents, etc., and those that have a stabilizing or protective effect on polymer degradation (antiaging additives), such as antioxidants and ultraviolet light protecting agents (4,5). Plasticizers are synthetic organic additives characterized by 600low molecular weight with low melting points or low volatility with high boiling points and high miscibility with the parent polymeric matrix [e.g., phthalic acid esters (PAEs)]. They are used to improve the plasticity (i.e., flow and workability) of polymers such as polyvinyl chloride (PVC), polyvinyl acetate (PVA), and polyvinyl alcohol (PVAL). In this way plastic formulations can contain up to 60% of plasticizer materials to transform an otherwise rigid polymer into a plastic with improved physical and mechanical properties such as flexibility, durability, and impact resistance (1,6). Plastics have revolutionized the packaging and transportation of foods, allowing foods to be packaged in lightweight materials while offering excellent physical protection against mechanical damage, water vapor transmission, and light oxidation. However, due to the relatively low molecular weight of residual polymeric monomers and certain additives (i.e., plasticizers and antioxidants), the migration to and absorption of these compounds by both solid and liquid foods is known to occur (7–9). This may result in off-odors or -flavors being imparted to the packaged food (10,11), resulting in the loss of product and sales. As well, the toxicology of these substances has been the subject of intense investigation in animal models (12–16) and human subjects (18–20). These issues gain relevance given the increased interest in irradiating packaged foods for increased microbiological safety (21–23). Gamma-irradiation of packaged foods is known to result in alterations such as the cross-linking and scission of polymeric materials and component additives which may in turn be adsorbed by the packaged food contained therein. This chapter discusses these issues as well as examining potential alternatives to the traditional polymeric packaging materials.
