## 4 Discussion  
Digestion processes are essential for isolating microplastics from food samples, but this methodology still requires optimization. Given the variability in food composition, it is necessary to determine the most suitable protocol for each type [19; 20]. Notably, the digestion of cheese matrices has not yet been thoroughly investigated. A search using the keywords \"MICROPLASTICS\" and \"CHEESE\" on both Scopus and Google Scholar databases revealed only one study (n = 1), which focused on milk. In this study, [PERSON] et al. (2021) [13] conducted the isolation of microplastics from milk using a two-step protocol involving multi-enzymatic and alkaline digestion. It was noted that foods with complex chemical compositions, such as milk and dairy products, may require the use of multiple reagents for organic matter removal [21]. However, an effective digestion protocol should ensure the highest percentage of digestion efficiency (% DE), using as few steps as possible. Further, a suitable digestion agent should ensure high efficiency in removing organic matter, while minimally impacting polymer integrity. In addition to this, a digestion can be considered efficient when no debris or organic matter is present, preventing interference with chemical analyses and allowing for the identification of pyrolysis products [22]. The multi-step digestion determines a higher risk of exposure to external contamination during sample preparation. Moreover, multi-step techniques, particularly those involving enzymes, are associated with high costs [23]. % DE can be affected by the chemical composition of the matrix. Therefore, the selection of digestion agents should be based on this consideration. Oxidizing digestion methods (such as H\({}_{2}\)O\({}_{2}\) and Fenton's reagent) are suitable for various chemical substrates, making them more versatile. Alkaline digestion techniques (e.g., KOH and sodium hydroxide) operate via saponification reactions and are therefore more effective on matrices with high levels of fats and proteins [24]. Our findings confirm that alkaline digestion is the most suitable method for removing organic matter from matrices rich in fats and proteins, such as cheese, compared to oxidizing approaches. It is important to specify that KOH was selected instead of sodium hydroxide because it has been shown to affect microplastics like PET and PS [22]. Furthermore, due to the fatty composition of cheese, ethanol (20 mL) was added to the digestate. This enhanced lipid dissolution, thereby facilitating filtration [25]. Sample preparation varies depending on the analytical approach used for the chemical identification of microplastics [26]. The constituents of organic matter influence the quantification of microplastics through visual observations and the detection of pyrolysis products. The quality of the Py-GC-MS spectrum depends on the percentage of organic matter removed. Indeed, it has been reported that Py-GC-MS analysis requires the complete isolation of microplastics from the organic matrix to minimize matrix effects and to pre-concentrate the microplastics [27; 28]. In our study, digestion using an aqueous solution of 5 M KOH at 50 \({}^{\circ}\)C enabled the identification of PET through the detection of benzophenone (\(m/z\) 182). A comparison of the mass spectrum obtained with the reference spectrum from the NIST MS/MS Spectral Library indicated a compatibility of 70%. However, PS was not detected. The characteristic pyrolysis product of PS (i.e., 2,4,6-triphenyl-1-hexene, \(m/z\) 91) was not identified in the mass spectrum. It was observed that the peak intensity of styrene trimers (such as 2,4,6-triphenyl-1-hexene) could be affected by the pyrolysis process [29]. Specifically, styrene trimers are formed via secondary reactions of pyrolysis. Therefore, sub-optimal experimental conditions may hinder the formation of styrene trimers [30]. As previously reported, digestive methods should minimally impact microplastics, which is important for assessing their original sizes [22].