## 2 Results
### Migration and Weight Increase of GPPS and HIPS in Contact with Real Food  
#### Migration and Weight Increase Using Milk, Cream and Olive Oil  
The migration kinetic of the lower molecular weight substances (toluene, chlorobenzene and styrene) was tested from GPPS and HIPS up to a storage time of 60 days into UHT milk with 3.5% fat content, UHT cream with 30% fat content and olive oil at 20 \({}^{\circ}\)C. Additionally storage conditions of 10 d at 40 \({}^{\circ}\)C were also investigated for the milk, cream and olive oil. At the same conditions, the weight increase of the polymer sheets before and after contact with the foods was measured. In Table 2 (GPPS) and Table 3 (HIPS) the relative migration for toluene, chlorobenzene and styrene and the weight increase after contact with each food is reported. The relative migration represents the percentage of substance that migrates from the polymer to the food. For styrene, the migrated amount into each food (in \(\mathrm{\SIUnitSymbolMicro g}\)/kg = ppb) is given as well. It was calculated considering the total surface of the specimens and applying the EU cube model: 6 \(\mathrm{\SIUnitSymbolMicro g}\)/kg. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Time/Temperature**} & \multicolumn{2}{c}{**Relative Migration [\%] into Milk (3.5\% Fat)**} & \multicolumn{2}{c}{**Migration of**} & \multicolumn{1}{c}{**Weight Increase**} \\  & **Toluene** & **Chlorobenzene** & **Styrene** & **Styrene [ug/kg]** & **[\%]** \\ \hline  
Migration into food from HIPS was higher compared to GPPS. The lowest migration of styrene was observed in milk after 15 days at 20 \({}^{\circ}\)C; it was approx. 90 \(\upmu\)g/kg from HIPS, roughly three times higher than from GPPS (approx. 30 \(\upmu\)g/kg). For both polymers, migration into milk (3.5% fat) was lower as into cream (with 30% fat content) and olive oil. Migration into cream and olive oil was comparable; the slightly higher values found in cream could be due to the uncertainty of the method, additionally the GPPS material after contact with cream and olive oil broke into pieces with the consequence that the \"edge effect\" increased. Migration of the investigated substances from GPPS after 10 days at 40 \({}^{\circ}\)C into food was higher compared to the condition 60 days at 20 \({}^{\circ}\)C. In olive oil and milk, the migration was twice as high compared to 20 \({}^{\circ}\)C. Migration of styrene from GPPS ranged from approx. 30 \(\upmu\)g/kg (in milk after 15 d at 20 \({}^{\circ}\)C) to approx. 220 \(\upmu\)g/kg (in cream after 10 d at 40 \({}^{\circ}\)C). No significant weight increase (<0.3%) was observed for GPPS at all the tested conditions using UHT milk, UHT cream and olive oil. However, GPPS material after contact with cream and olive oil became significantly brittle and broke into pieces. Therefore, it was not possible to determine precise weight increase of GPPS in these foods. Migration of the investigated substances from HIPS after 10 days at 40 \({}^{\circ}\)C into food was comparable to the migration extent at the condition 60 days at 20 \({}^{\circ}\)C. In case of styrene it was equal to approx. 150 \(\upmu\)g/kg, 270 \(\upmu\)g/kg and 220 \(\upmu\)g/kg, respectively, in milk, cream and olive oil. These values correspond to a relative migration of approx. 3.6%, 6% and 5%, respectively. No significant weight increase (<0.6%) was observed for HIPS at all the tested conditions using UHT milk, UHT cream and olive oil except at 60 days at 20 \({}^{\circ}\)C with olive oil. In this case, a weight increase of 2.3% was determined. No visual changes in appearance of GPPS or HIPS with all the tested foods were observed.