606 Novel food packaging techniques substances like toluene are almost completely removed during washing, so that an evaluation of the cleaning effect during remelting on basis of these surrogates is impossible In conclusion, conventional washing processes are able to reduce the input oncentrations of post-consumer substances in flakes. The washing process itself most probably removes only contaminants on the surface of the flakes whereas thermal drying processes are also able to decrease substance which sorbed into the flakes. Remelting processes further reduce the contamination. Due to the fact that conventional recycling processes use a wide range of parameters and quipment, a general conclusion and a quantification of the cleaning effects for washing, drying and remelting processes is not possible on basis of the above mentioned results 23.4.3 Cleaning efficiency of super-clean processes In the last decade studies were undertaken to quantify the residual amounts of chemical substances in the material after deep-cleansing. Therefore the cleaning efficiency of super-cleaning recycling processes is well known Additionally to the challenge test, the quality assurance of post-consumer ecycle(PCR) PET is based on a feedstock control and an analytical quality assurance. Literature data about cleaning efficiencies of super-clean recycling processes are very rare. Three studies of the cleansing efficiency of super-clean recycling processes for PET are published by Franz and process investigated in the first two studies" contains the key steps: washing, re-extrusion and solid state polycondensation(SSP). The process was challenged with three different surrogate concentration levels. as a result the cleaning efficiencies for the different surrogates and contamination levels are between 94 and 99%. The most challenging substance is benzophenone. The results show no significant dependency on the input concentration of the surrogates going into the process. It should be noted here, that this process was tested without a washing process. Including a conventional washing process, the cleaning efficiencies are increased to more than 99.3% even for benzophenone. In the third study" a recycling process without solid stating was investigated. Except for benzophenone, the investigated recycling process reduces all surrogates by more than 95% for initial concentrations below 100 ppm and more than 90% for initial concentrations between 100 and 500 ppm. For that most challenging substance, benzophenone, a cleaning efficiency of approximately 77% at an initial contamination level of 294 ppm was obtained. In conclusion the determined cleaning efficiencies are lower than those of processes with solid stating. However, the specific migration of all surrogates from PET bottles made from contaminated and recycled PET was detected to be far below the migration limit of 10 ppbsubstances like toluene are almost completely removed during washing, so that an evaluation of the cleaning effect during remelting on basis of these surrogates is impossible. In conclusion, conventional washing processes are able to reduce the input concentrations of post-consumer substances in flakes. The washing process itself most probably removes only contaminants on the surface of the flakes whereas thermal drying processes are also able to decrease substance which sorbed into the flakes. Remelting processes further reduce the contamination. Due to the fact that conventional recycling processes use a wide range of parameters and equipment, a general conclusion and a quantification of the cleaning effects for washing, drying and remelting processes is not possible on basis of the above mentioned results. 23.4.3 Cleaning efficiency of super-clean processes In the last decade studies were undertaken to quantify the residual amounts of chemical substances in the material after deep-cleansing. Therefore the cleaning efficiency of super-cleaning recycling processes is well known. Additionally to the challenge test, the quality assurance of post-consumer recycle (PCR) PET is based on a feedstock control and an analytical quality assurance. Literature data about cleaning efficiencies of super-clean recycling processes are very rare. Three studies of the cleansing efficiency of super-clean recycling processes for PET are published by Franz and Welle.20,21,22 The process investigated in the first two studies20,21 contains the key steps: washing, re-extrusion and solid state polycondensation (SSP). The process was challenged with three different surrogate concentration levels. As a result the cleaning efficiencies for the different surrogates and contamination levels are between 94 and 99%.20 The most challenging substance is benzophenone. The results show no significant dependency on the input concentration of the surrogates going into the process. It should be noted here, that this process was tested without a washing process. Including a conventional washing process, the cleaning efficiencies are increased to more than 99.3% even for benzophenone. 21 In the third study22 a recycling process without solid stating was investigated. Except for benzophenone, the investigated recycling process reduces all surrogates by more than 95% for initial concentrations below 100 ppm and more than 90% for initial concentrations between 100 and 500 ppm. For that most challenging substance, benzophenone, a cleaning efficiency of approximately 77% at an initial contamination level of 294 ppm was obtained. In conclusion the determined cleaning efficiencies are lower than those of processes with solid stating. However, the specific migration of all surrogates from PET bottles made from contaminated and recycled PET was detected to be far below the migration limit of 10 ppb. 506 Novel food packaging techniques