## 3 Results and Discussion
### Volatile Compounds of Cold Brew Samples  
Many operations and parameters affect the final product, changing the chemical composition of raw materials and intermediates before the end of the technological process. During roasting, the Maillard reaction, caramelization and other chemical reactions dramatically change the coffee beans' composition, as well as the colors and volatiles of green coffee beans. As a result, desirable and potentially dangerous compounds are formed. For example, [PERSON] et al. [22] studied \(\alpha\)-dicarbonyl compounds and 4-methylimidazole in coffee made with various roasting and brewing conditions. In general, the espresso method, using smaller coffee bean particles, led to significantly higher concentrations of \(\alpha\)-DC and 4-MI than cold brewing, and in the cold brew method, the highest concentrations of \(\alpha\)-DC and 4-MI were found with the largest coffee bean particles. The average total \(\alpha\)-DC concentration in their cold brew was 37.5 \(\upmu\)g/mL and in 4-MI was 59.6 \(\upmu\)g/mL. These contents were higher due to higher roasting temperatures (235 \({}^{\circ}\)C/13 min, 240 \({}^{\circ}\)C/15 min, 245 \({}^{\circ}\)C/17 min).  
Regardless of coffee bean quality, [PERSON] et al. [23] determined the sensory profile, physicochemical characteristics, and volatile and non-volatile compounds in two brewing methods: cold and hot. Their coffee beverages were more differentiated by brewing method than by the coffee bean quality used in the preparation. Cold brew coffees were mainly associated with volatile 2-methyl-butanol, 5-methyl furufural and dihydro-2-methyl-3 (2H)-furanone followed by relative percentage concentration, respectively: 3.4-42%, 14.49-14.68% and 1.1-1.13%. Hot brew coffee beverages were identified with some specific furans and 2-methoxy-4-vinylphenol. We didnot find 2-methoxy-4-vinylphenol in our research but did find some furans.  
To date, many studies on volatiles have shown that furans and 5-hydroxymethylfurfurral (5-HMF) were found, for example by [PERSON] et al. [24]. Authors ranged from levels of 5-HMF in coffee samples between 51 and 1143 mg/L. We agree with the presented research because the higher temperature of roasting coffee causes the increase in the mentioned compounds and others as a result of the Maillard reaction. It is worth noting that cold brew contains less of these compounds compared to hot coffee [25].  
Figure 6 below shows an interesting proposition of the main volatile compounds' (VOCs') formation reactions in coffee based on other authors [18].  
During production, many operations and parameters influence the final product, changing the chemical composition of raw materials and intermediates before the end of the technological process. The different extraction conditions used by independent producers of a coffee beverage can indicate a different composition of volatile compounds. The experiment was designed to highlight the importance of different extraction methods to detect and characterize particular compounds. Generally, a test for VOCs was performed in a similar matrix to caffeine and chlorogenic acid (three roast profiles \(\times\) three extraction times \(\times\) three extraction temperatures) and the results are shown in Table 4 below.  
Selected compounds from all of the marked volatile compounds belong to the following groups.