## 4 PAH Occurrence and Formation in Processed Meat, Edible Oils, and Cereal-Derived Products
### Features Underlying PAH Formation in Cereal and Cereal-Derived Products  
Existing research examining PAH occurrence in cereal products attaches high importance to PAH formation throughout the food chain. Similar to meat products and edible oils, PAH contamination in cereal and cereal-derived products mainly differs depending on the processing technique [175]. At this stage, the quality of cereal-derived products is greatly influenced by their pre-processing method [195]. Aside from the temperature reached during drying, processing, or cooking, PAH contamination of cereal products is also affected by the type of fuel and the method of heat delivery [125; 156; 196]. Figure 6 provides an overview of the representative features modulating PAH levels in cereal and cereal-derived products undergoing thermal processing. Further, additional factors pertaining to PAH formation and occurrence are described. In corn, [PERSON] et al. (2017) reported PAH levels within the range of 5.9-127 ug/kg as a result of the drying process [197]. Other raw materials, including wheat and rye grains, bran, and flour, ranged from 1.07 to 3.65 ug/kg [198]. In addition, wheat, rye, and the resulting bread products were found to contain PAH levels between 0.22 and 1.62 ug/kg [199]. Similarly, [PERSON] et al. (2018) analyzed the PAH content in cereal products as a sum of eight PAHs, including barley (0.11 ug/kg), brown rice (1.26 ug/kg), and instant noodles (2.38 ug/kg) collected from the Korean market [24]. Notably, in cereal samples collected from Pakistani households, the highest total PAH levels were detected in wheat (169 ug/kg), followed by maize (159 ug/kg) and rice (53 ug/kg) [200]. The levels of PAHs in wheat grain samples collected in Poland showed similar profiles for 2017 and 2018 harvests, ranging between 9 ug/kg and 11 ug/kg EU PAH (15+1) [121]. In addition, toasted guarana seeds subjected to husk removal resulted in 0.78 ug/kg PAHs, as opposed to unhused seeds, where no PAHs were detected [201]. Other studies place PAH contamination in cereal-based products within different ranges based on the employed processing technique and type of fuel [175; 176; 202]. In order to maintain a certain moisture degree for preservation, grains are subjected to drying for moisture reduction involving high temperatures, which in turn promote PAH formation [175]. The accumulation of PAHs in rice under various drying conditions showed increasing PAH levels depending on the heating source in the order electric heating (7.7 ug/kg), liquefied petroleum gas (15.9 ug/kg), rice husk (45.7 ug/kg), and wood (131.6 ug/kg) [203]. Furthermore, the drying temperature showed no significant differences in PAH accumulation, whereas polishing resulted in reduced PAH content in rice when compared to parboiling [203]. In bread, PAH levels may range from 1.59 to 365 ug/kg under the effect of raw materials, the bread type, thermal treatment, and microbial culture during fermentation, as well as the heating source during thermal processing [156; 198]. [PERSON] et al. (2018) found that home toasting elevated the content of PAHs in bread depending on the raw material, with the highest levels in white bread (17.8 ug/kg), followed closely by wholegrain bread (16.9 ug/kg), multiseed bread (16.5 ug/kg), black bread (13.0 ug/kg), and sliced bread (10.3 ug/kg) [125]. The effect of raw materials on PAH levels in bread revealed lower  
Figure 6: Flowchart showing the representative factors influencing PAH formation in cereal and cereal-derived products undergoing thermal processing. contamination in Baltonowski bread and wholeneal rye bread compared with plain rye bread. Moreover, irrespective of the baking temperature, the crumb had lower PAH levels than the loaf and crust [198]. In addition, increasing the baking temperature resulted in proportionally elevated PAH content irrespective of the bread type [198].