## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Food** & **Testing** & & & **Relative Migration of Styrene [\(\%\)]\({}^{1}\)** & & \\
**(Simulant)** & **Conditions** & **PS-S-11** & **PS-S-22** & **PS-S-32** & **PS-P-11** & **PS-P-22** & **PS-P-32** \\ \hline
20\% Ethanol & 10 days/20 \({}^{\circ}\)C & 0.2 & 0.2 & 0.3 & 0.3 & 0.6 & 0.5 \\
20\% Ethanol & 10 days/40 \({}^{\circ}\)C & 0.4 & 0.5 & 0.5 & 1.3 & 2.6 & 2.6 \\
50\% Ethanol & 10 days/40 \({}^{\circ}\)C & 1.0 & 1.1 & 1.0 & 3.1 & 5.7 & 5.6 \\ Yoghurt & 10 days/8 \({}^{\circ}\)C & 0.1 & 0.1 & 0.1 & 0.1 & 0.1 & 0.2 \\ Yoghurt & 20 days/8 \({}^{\circ}\)C & 0.1 & 0.2 & 0.2 & 0.1 & 0.2 & 0.3 \\ Yoghurt & 30 days/8 \({}^{\circ}\)C & 0.1 & 0.2 & 0.3 & 0.2 & 0.3 & 0.2 \\ Yoghurt & 40 days/8 \({}^{\circ}\)C & 0.1 & 0.2 & 0.2 & 0.2 & 0.2 & 0.3 \\ Yoghurt & 50 days/8 \({}^{\circ}\)C & 0.1 & 0.3 & 0.4 & 0.3 & 0.4 & 0.4 \\ \hline \hline \end{tabular} \({}^{1}\) Calculated by dividing the mass of styrene found in the food (simulant) by the initial mass determined in the sample material (considering the area weight of each sample material).  
\end{table} 
Table 3: Relative migration of styrene as a percentage. The migration of styrene in food simulants and in yoghurt was tested using extruded sheets and thermoformed pots made of PS (using three types of pots manufactured from the corresponding sheets). For compliance testing according to the EU Food Contact Regulation [1], standardized experimental conditions and proper food simulants must be chosen, depending on the food contact applications and time/temperature conditions of use. During the industrial production and filling of stirred yoghurt, the temperature at the point of contact with the PS containers does not exceed 20 \({}^{\circ}\)C (in the first hours); the subsequent storage usually takes place below 5 \({}^{\circ}\)C. The common shelf life given by producers is about 40-50 days [19]. For household refrigerators, 8 \({}^{\circ}\)C is a representatively conservative temperature. These filling, fermentation, and storage conditions are tested using the standardized condition of 10 days/40 \({}^{\circ}\)C, which also covers hot-fill conditions according to Regulation 10/2011 (Annex V, chapter 2.1.4 (b)). For yoghurt (ref. food category N. 07.02, shown in Table 2 of Annex III) the simulant D1 (50% ethanol) is specified and was used for the study. Simulant B, for the acidic character of yoghurts, was not considered in this study as the solubility of styrene is worse in 3% acidic acid compared to yoghurt or ethanol-water mixtures. Styrene, with a Log K\({}_{\rm o/w}\) of 2.95, dissolves only slightly in water. However, it is soluble in alcohol. In the scientific literature, it has also been reported that testing styrene migration from PS by employing aqueous food simulants may lead to underestimation of the migration processes occurring in real food products [9; 10; 11; 12; 13]. As it has already been shown in previous studies that 50% ethanol swells the surface and leads to exaggerated migration values in relation to real foods [17], in the present study, 20% ethanol for 10 days/40 \({}^{\circ}\)C and for 10 days/20 \({}^{\circ}\)C were tested additionally as less severe simulants. According to Regulation 10/2011 (Annex III), 20% ethanol (food simulant C) should be used for alcoholic foods with an alcohol content of up to 20% and for those foods containing a relevant amount of organic ingredients that render the food more lipophilic, while 50% ethanol (food simulant D1) should be used for alcoholic foods with an alcohol content of above 20% and for oil-in-water emulsions, including milk products (Annex III, Tables 2 and 3 of the Regulation). However, for some substances listed in Annex I, additional rules are given (Table 1, column 11) that should be respected in situations where there is a risk of non-compliance.