## 4 PAH Occurrence and Formation in Processed Meat, Edible Oils, and Cereal-Derived Products
### Features Underlying PAH Formation in Meat and Meat-Derived Products
The impact of time is also evident during smoke curing. Pork sausages show an increasing trend in PAH accumulation with the extension of the smoking time [107]. Similarly, prolonged smoking from 0 to 5 days revealed a considerable increase in BaP levels in smoked meat samples, followed by a decreasing trend up to day 7 [139]. Another important factor to consider is the type of fuel. Unlike spontaneous combustion, the pyrolytic process may involve secondary condensation and cyclodehydrogen reactions to afford more condensed and relatively stable HMW PAHs [1; 138]. In a typical combustion process for open wood burning, hemicellulose degrades first, then cellulose, and finally, lignins [138; 152; 153]. Prior to the generation of the final PAHs, precursor and intermediate compounds go through a number of primary and secondary processes that have an impact on pyrolysis-derived chemicals [138]. In the case of smoking, irrespective of moisture and chip size [153; 154], the effect of temperature is translated into the choice of wood type. In turn, this may lead to significant variations in PAHs, depending on the associated smoke generation temperature [109; 154]. For instance, the use of wood containing low cellulose and hemicellulose contents determines the formation of lower PAH levels than other wood types [109; 154]. In the same vein, three charcoal classes promoted PAH accumulation during grilling, irrespective of the meat product (pork, beef, or chicken), depending on the charcoal type in the order white > black > extruded [93]. Under such conditions, however, the type of fuel should be assessed in conjunction with additional parameters, such as the distance of the product from the heat source, the fat content of the sample, the batch cooking order, and the presence of skin or casing, among others [108; 136; 147; 151; 155]. Moreover, foods prepared using open-flame sources are linked to elevated PAH levels as a result of smoke production from fuel combustion and fat droplets [7; 156]. Smoke and PAHs migrate together and settle on the food surface before potentially being retained in the hydrophobic (fat-rich) areas [15; 85; 137; 155]. Alternatively, gas used as an open-flame heating source could minimize the production of PAHs compared to charcoal and wood [7; 157]. Unlike a charcoal- or wood-generated open flame, by using gas nozzles to create and spread the flame, flame-free areas are created between each nozzle (small gas flame). This may decrease the contact between the flame and fat droplets [157]. Limiting the direct contact between meat and smoke could aid in reducing the PAH content in grilled meat products [99]. Consequently, cooking techniques not involving smoke generation, such as infrared and electric heating, are advised to inhibit PAH formation [7]. The contents of PAHs produced during processing also vary depending on the nature of the food material. In fat-rich food products, the lipidic constituents act as PAH carriers, resulting in their accumulation in both raw and processed products. Moreover, the amounts of PAHs are influenced by the fatty acid profile of the fat [7; 158]. Alternatively, the use of low-fat approaches can lead to reduced PAH levels. In addition, some practices involve replacing animal fat with vegetable oils in certain meat-derived products, such as sausages, patties, etc. In turn, the stability of the final product to high-temperature cooking is enhanced, whereas the sensory characteristics are fairly well maintained [7; 159]. With a less significant impact compared with fat content, protein types and levels also influence PAH formation in food [158; 160]. Although less studied, the protein content has been associated with increased protein carbonyl levels in deep-fried meat products, along with elevated lipid peroxidation values [97], suggesting its contribution. Moreover, additional investigation of amino acid profiles during thermal processing might impart further insight on the mechanistic implications of the resulting PAH accumulation [161].