## 1 Introduction  
The production of a food contact material (FCM) typically passes through numerous processing stages. In Europe, the compliance of FCMs with the applicable legal requirements must be assured at each stage of the supply chain. Plastics Regulation (EU) No. 10/2011 (for plastics used in applications with food contact) requires a written declaration of compliance (DoC), which is to be provided at all stages of the supply chain excluding the retail stage [1]. Therefore, each manufacturer must declare compliance with respect to their responsibility and role in the supply chain. Communication through the production chain is essential, clarifying what work has been performed and what tasks are delegated to actors further down the supply chain [2]. The compliance of FCMs can be verified by migration testing. The above Plastics Regulation sets a maximum overall migration limit (OML) and specific migration limits (SMLs) for toxicologically relevant substances. Furthermore, it describes the required testing procedure [1]. Migration testing in food legally prevails. However, migration is usually tested with'simulants', which are used to represent defined food categories. The migration testing is performed under standardized time/temperature conditions, chosen depending on the intended specific food use and the maximum shelf-life of packaged food. Yogurts and similar dairy products are usually stored at refrigerated temperatures, with shelf-lives of about 40 to 50 days. The official simulant for milk products is 50% ethanol (simulant D2). The contact condition of 10 days at 40 \(\mathrm{\SIUnitSymbolCelsius}\) represents long-term storage for more than 30 days in refrigerated conditions, according to Regulation (EC) No 10/2011, Annex V.2.1.4 [1]. High-impact polystyrene (HIPS) is used for packaging fresh dairy products like yoghurt, buttermilk, puddings, and dairy desserts in small cups, pots, or tubs [3]. Crystal polystyrene (or general-purpose polystyrene, GPPS) is converted to HIPS by adding impact modifiers like butadiene rubber in order to improve the flexibility of the materials. Commercial HIPS grades are usually blended further with additional GPPS at the stage of the production of sheets for dairy applications. The final cups are directly thermoformed from sheets at the cremery in form-fill-seal (FFS) packaging machines, with subsequent filling of the product and sealing while in-line; alternatively, dairy manufacturers buy preformed cups from packaging material converters and then only have to fill and seal them [4]. Polystyrene contains residues of styrene monomer, which partially migrate from the food contact article into the foodstuff. A precautionary specific migration limit (SML) for styrene of 40 \(\upmu\)g/kg has been recently proposed by the EU Commission [5]. The European Food Safety Authority (EFSA) is currently evaluating the available studies to assess the genotoxicity potential of styrene after oral exposure to foods in plastic FCMs [6]. The residual levels in the PS material, the characteristics of the polymer, and food properties such as fat content, as well as the contact temperature and the duration of storage of the packed food are the main factors influencing the migration of styrene [7; 8; 9; 10; 11; 12; 13; 14; 15]. The latest research reveals that when testing PS materials with food simulants under the conditions defined by Regulation (EC) No 10/2011, there is a risk of obtaining overly high migration results for styrene that are not comparable to the level of migration seen into real food [16; 17; 18; 19]. In a previous study [20], we found that the levels of styrene migrating into different refrigerated dairy products (packed in PS pots) ranged from 2.8 \(\upmu\)g/kg to 22.4 \(\upmu\)g/kg; in contrast, when PS pots were tested with food simulants comprising 10%, 20%, and 50% ethanol for 10 days at 40 \({}^{\circ}\)C, the migration results were higher and, in most cases, exceeded 40 \(\upmu\)g/kg.