T. OZCAN et al.: The formation of polycyclic hydrocarbons, Mljekarstvo 61 (3), 193-198 (2011) 193 Review - Pregledni rad UDK: 637.3.07 The formation of polycyclic hydrocarbons during smoking process of cheese *Corresponding author/Dopisni autor: Phone/Tel.: 00 90 224 29 41 498; E-mail: tulayozcan@uludag.edu.tr Tulay Ozcan*, Arzu Akpinar-Bayizit, Oya Irmak Sahin, Lutfiye Yilmaz-Ersan Uludag University, Department of Food Engineering, 16059, Görükle, BURSA-TURKIYE Received - Prispjelo: 04.02.2011. Accepted - Prihvaćeno: 19.07.2011. Introduction The smoking of foods is one of the oldest meth- ods of preservation. However, foods are nowadays smoked for sensory quality rather than for the pre- servative effect. Sensory characteristics are one of the important quality attributes that a consumer uses to judge the acceptability of a product. Colours of smoked cheese available in the market range from golden yellow to dark brown, and this array of col- ouration suggests that producers of smoked cheese have different opinions concerning consumer pref- erences. Similar to colour cheese flavour is diversi- fied by smoking (Möhler 1980; Asita et al., 1990; Müller 1991; Riha and Wendorff, 1993; Reh- man et al., 2003; Ozcan et al., 2008). In the analysis of smoked cheese with head- space-solid phase extraction method a broad range of compounds, such as acids, alcohols, esters, hydro- carbons, aldehydes, ketones, furan and pyran deriva- tives, terpenes and sesquiterpenes as well as ethers, of diverse volatility, molecular weights and nature were determined (Guillen and Sopelana, 2005). Summary The smoking process determines the characteristic flavour, odour, colour and texture of sev- eral cheese varieties. Some smoke compounds are known to have bacteriostatic and antioxidant ef- fects, and may act as preservatives. Smoked cheese is appreciated by consumers due to its sensorial properties. However, with smoking process there is a risk of formation of toxic polycyclic aromatic hydrocarbons (PAHs). This review emphasises the occurrence of polycyclic hydrocarbons on smoked cheeses and their health impacts. Key words: cheese, smoking process, polycyclic hydrocarbons Polycyclic aromatic hydrocarbons (PAHs), that are composed of two or more fused aromatic rings (EC, 2002; EFSA, 2008) and having a strong lipophilic character (Simko, 2005), constitute a widespread group of contaminants (Guillen et al., 1997). PAHs are formed by incomplete combus- tion or pyrolysis of organic material. With tradi- tional smoking process applied to any food material, in which food and the smoke comes in direct con- tact, toxic PAHs are formed. Temperature, humid- ity, type of wood/coal, oxygen concentration during smoke generation, and the type of smoke generators are effective on formation of possible PAHs (Toth and Potthast, 1984; Chiu et al., 1997; Ozcan et al., 2008; Duedahl-Olesen et al., 2010). It is worth to mention that some PAHs are able to interact with organisms through enzymes (such as aryl hydrocarbon hydroxylases) to form PAH dihy- drodiol derivatives. These reactive products are able to form covalent bounds with proteins and nucleic acids which typify them as carcinogens. In general, the alterations of DNA expressions are thought to be involved in cell mutation which results malig-