## 3 Discussion
The strong swelling of GPPS at 60 \({}^{\circ}\)C related to the lower temperatures and related to HIPS is explained by solvent crazing and stress cracking [44]. Looking at the migration and weight increase using 95% ethanol, a similar behavior was observed for GPPS and HIPS. 95% ethanol is more polar compared to isooctane, but still causes weight increase (and therefore swelling) of both polymers at all tested temperatures. At all tested temperatures relative migration values are high but depending on the nature of the substances. The time dependent migration of the most volatiles (toluene, chlorobenzene, styrene) was bigger compared to the higher molecular weight test substances (phenyl cyclohexane, benzophenone and methyl stearate with 160, 182 and 298 g/mol respectively). According to the Regulation (EU) 10/2011, 50% ethanol is assigned to the food category dairy products. The EU 10/2011 test scheme foresees for specific migration, accelerated test conditions at elevated temperature. For example, testing for 10 days at 60 \({}^{\circ}\)C simulate contact times longer than 30 days at room temperature and below, while testing for 10 days at 40 \({}^{\circ}\)C shall cover all storage times at refrigerated and frozen conditions including hot-fill conditions and testing for 10 days at 20 \({}^{\circ}\)C all storage times at frozen condition. Using 50% ethanol, only little weight increase at 60 \({}^{\circ}\)C, 40 \({}^{\circ}\)C and 20 \({}^{\circ}\)C was found for both the polymers investigated in the present study. Contrary, none of the tested foods did cause a significant weight increase of GPPS or HIPS material or did induce visual changes under real conditions of usage. Alternative testing conditions (milder compared to the conventional) for the simulants 95% ethanol and isooctane depending on the polarity of the polymer are proposed in the draft document \"Technical guidelines for compliance testing\" [8] in consideration of the swelling effect or as substitute test when oil testing is not feasible. In these guidelines, the polymers are divided into two groups, those that contain carbon and hydrogen only and those that contain additionally other atoms. Both polystyrenes, GPPS and HIPS belong to the first group. According [8], migration testing for the long-term storage condition 10 days/60 \({}^{\circ}\)C shall be carried out with 95% ethanol under the same time-temperature conditions as oil, while with isooctane at 10 days/20 \({}^{\circ}\)C. For screening purposes, testing conditions are specified for the polystyrene polymer: 10 days at 60 \({}^{\circ}\)C, 40 \({}^{\circ}\)C and 20 \({}^{\circ}\)C in oil are reduced to 1 day for both 95 % ethanol and isooctane, except for 95 % ethanol at 20 \({}^{\circ}\)C, which shall be tested with 10 days contact. In Table 6 migration of styrene in food simulants and real foods at different time/ temperature testing conditions, swelling (as % weight increase) and visual changes of the sample material are reported. For the food simulants, not always exactly 10 days were measured; data were in this case extrapolated. For the alternative fatty food simulants (95% ethanol and isooctane) official and alternative testing conditions are summarized. The alternative testing conditions are in accordance with the draft guideline [8] (page 59 Table 7: \"Test conditions for screening food simulants compared to vegetable oil for specific migration\"). The alternative fatty food simulants isooctane and 95% ethanol cause significant swelling of the HIPS polymer (both considering official and alternative testing condition), which is further increased by higher contact temperatures. The effect is that obtained migration values tend to overestimate the actual migration into real foods. In real foods even after 10 days contact at 40 \({}^{\circ}\)C the weight increase remained below 1%. In case of HIPS, isooctane overestimate real migration into foods at all temperatures. Concerning GPPS, the migration levels as well as the swelling effect of isooctane strongly depend on the temperature.