Recycli significant concentrations, which are linked to sorbed compounds from the first use of the packaging materials(see Section 23. 2.2). A deep cleansing of these polymers might influence the sensory properties in a positive way. However the sensory properties of recycled polymers are a crucial parameter for a closed loop recycling and should be investigated in case by case studies with the final recyclate containing packaging materials. This is due to the fact that odour threshold limits of some flavour compounds are very low and, in a few cases below the analytical detection limits so that the results of the challenge test cannot be used for the sensory evaluation of recycled polymers As an important consequence, to comply with the legal requirements of any legislation sufficient sensory inertness of the recycled PEt product of food contact articles needs to be assured and this can only be achieved by appropriate sensory testing. Test conditions which in many cases can serve as worst case is storage of the article in direct contact with an appropriate food simulant (for instance water as a most severe test medium) for 10 days at 40oC.However depending on the particular application modified tests may be more suitable 23.5 USing recycled plastics in packaging Technically, recycled plastics can, in principle, be applied in direct food contact applications or protected from direct food contact by a functional barrier. From a legal point of view, there may be limitations due to different regulations in the European countries and the still missing harmonised rules for EU. In any case the use of recycled plastic materials in packaging applications has to comply with the relevant regulations and must not be at the expense of the public health, nor should it alternate the filling's quality. In the following, practical examples of recycled plastics food packaging applications covered by a functional barrier as well as in direct food contact are described 23.5.1 Indirect contact applications applying functional barriers In the most general understanding the concept of a functional barri er can be defined as follows: A functional barrier is a layer in the package which protects the food from external influences under the applied fill and storage conditions In most cases the functional barrier is the food contact layer or, in complex multi-layer structures, one very close to it. This layer acts as a barrier against contamination from the packagings environment in general and,more pecifically, from the recycled core layer or outer compartments of the package The functional barrier efficiency must not be confused with an absolute physical barrier such as glass or metal layers. It is related to a ' functional quantity in terms of mass transfer which is dependent on the technological and application-related parameters of the respective food-package system. These parameters aresignificant concentrations, which are linked to sorbed compounds from the first use of the packaging materials (see Section 23.2.2). A deep cleansing of these polymers might influence the sensory properties in a positive way. However the sensory properties of recycled polymers are a crucial parameter for a closed loop recycling and should be investigated in case by case studies with the final recyclate containing packaging materials. This is due to the fact that odour threshold limits of some flavour compounds are very low and, in a few cases, below the analytical detection limits so that the results of the challenge test cannot be used for the sensory evaluation of recycled polymers. As an important consequence, to comply with the legal requirements of any legislation sufficient sensory inertness of the recycled PET product of food contact articles needs to be assured and this can only be achieved by appropriate sensory testing. Test conditions which in many cases can serve as worst case is storage of the article in direct contact with an appropriate food simulant (for instance water as a most severe test medium) for 10 days at 40ºC. However, depending on the particular application modified tests may be more suitable. 23.5 Using recycled plastics in packaging Technically, recycled plastics can, in principle, be applied in direct food contact applications or protected from direct food contact by a functional barrier. From a legal point of view, there may be limitations due to different regulations in the European countries and the still missing harmonised rules for EU. In any case, the use of recycled plastic materials in packaging applications has to comply with the relevant regulations and must not be at the expense of the public health, nor should it alternate the filling’s quality.31 In the following, practical examples of recycled plastics food packaging applications covered by a functional barrier as well as in direct food contact are described. 23.5.1 Indirect contact applications applying functional barriers In the most general understanding the concept of a functional barrier can be defined as follows: A functional barrier is a layer in the package which protects the food from external influences under the applied fill and storage conditions. In most cases the functional barrier is the food contact layer or, in complex multi-layer structures, one very close to it. This layer acts as a barrier against contamination from the packaging’s environment in general and, more specifically, from the recycled core layer or outer compartments of the package. The functional barrier efficiency must not be confused with an absolute physical barrier such as glass or metal layers. It is related to a ‘functional’ quantity in terms of mass transfer which is dependent on the technological and application-related parameters of the respective food-package system. These parameters are: Recycling packaging materials 509