Packaging-flavour interactions 145 Polymer Migrating Adverse Foodstuff substance PERMEATION OxvoCn (1)Oxidation Water vapour microbial growl arbon dioxide Mould growth (2) Dehydration Decarbonation MiGrAtion Monomers ABSORPTION Aroma compounds Loss of aroma int (SCALPING Fats Ir ganic acids Dainage to the package Fig. 8.1 Possible interactions between foodstuff, polymer film and the environment, together with the adverse consequences(Nielsen and Jagerstad, 1994) adsorb and dissolve into the polymer mass. In the polymer film, the molecules hop or diffuse randomly as their own kinetic energy keeps them moving from vacancy to vacancy as the polymer chains move. The movement of the molecules depends on the availability of vacancies or holes'in the polymer film. These holes' are formed as large chain segments of the polymer slide over each other due to thermal agitation. The random diffusion yields a net movement from the side of the polymer film that is in contact with a high concentration or partial pressure of permeant to the side that is in contact with a low concentration of permeant. The last step involves desorption and evaporation of the molecules from the surface of the film on the downstream side(Singh and Heldman, 1993) Absorption involves the first two steps of this process, i.e. adsorption and diffusion, whereas permeation involves all three steps(delassus, 1997) 8.2 Factors affecting flavour absorption As polymer packaging is more and more widely used for direct contact with foods, product compatibility with the packaging material must be considered Flavour scalping, or the absorption of flavour compounds, is one of the most important compatibility problems. The problem of aroma absorption by plastic packages has been recognised for many years ( Johansson, 1993). Several research groups throughout the world investigated flavour absorption phenomena extensively. It is a complex field, and several factors have beenadsorb and dissolve into the polymer mass. In the polymer film, the molecules ‘hop’ or diffuse randomly as their own kinetic energy keeps them moving from vacancy to vacancy as the polymer chains move. The movement of the molecules depends on the availability of vacancies or ‘holes’ in the polymer film. These ‘holes’ are formed as large chain segments of the polymer slide over each other due to thermal agitation. The random diffusion yields a net movement from the side of the polymer film that is in contact with a high concentration or partial pressure of permeant to the side that is in contact with a low concentration of permeant. The last step involves desorption and evaporation of the molecules from the surface of the film on the downstream side (Singh and Heldman, 1993). Absorption involves the first two steps of this process, i.e. adsorption and diffusion, whereas permeation involves all three steps (Delassus, 1997). 8.2 Factors affecting flavour absorption As polymer packaging is more and more widely used for direct contact with foods, product compatibility with the packaging material must be considered. Flavour scalping, or the absorption of flavour compounds, is one of the most important compatibility problems. The problem of aroma absorption by plastic packages has been recognised for many years (Johansson, 1993). Several research groups throughout the world investigated flavour absorption phenomena extensively. It is a complex field, and several factors have been Fig. 8.1 Possible interactions between foodstuff, polymer film and the environment, together with the adverse consequences (Nielsen and Ja¨gerstad, 1994) Packaging-flavour interactions 145