## 4 Discussion
For example, ethyl decanoate (from 2.8% to 23.4%) is associated with an apple aroma while linalool was found only in IPA (0.8%) with citrus and rose aromas [16]. Free fatty acids represent one group of beer flavor that affect beer taste and stability over time; medium-chain acids such as hexanoic, octanoic and decanoic acids are formed during fermentation. In our study, octanoic acid and hexadecenoic acids have been found to reach the highest value in the ACD sample (13.3% and 10.5%, respectively). In general, they have rancid flavor characteristics, and their formation is influenced by more factors, such as yeast strain, word composition and the degree of aeration [17; 18]. Different chemical families have an important impact on beer aroma properties [19]; for example, the esters ethyl hexanoate and ethyl octanoate (percentages in LKO \(>\) ACD \(>\) IPA) are responsible for sour apple aromas while 2-phenylethanol (percentages in LKO \(>\) ACD \(>\) IPA) and phenylethylal acetate (percentages in ACD \(>\) IPA \(>\) LKO) are responsible for rose aromas. Among long-chain fatty acids, we found hexadecanoic acid (palmitic acid) only in IPA (73.3%). This result agrees with what is shown by the analysis of dried hop TP (Table 1) used for the production of this type of beer and the only variety where this fatty acid has been detected (16.1%). On the other side, the investigation performed on hop methanol extracts (Table 3) showed an ubiquitous presence of sesquiterpenes in high percentages, including \(\beta\)-caryophyllene, humulene, \(\beta\)-eudesmene and caryophyllene oxide as the major exponents. These data are in agreement with those reported by [PERSON] et al. [20], who listed these compounds as the most important for hop aroma. Other minor compounds, such as 2-methylbutanoic acid, 3-methylbutanoic acid and 2-methylpropanoic acid, detected in variable percentages in the extracts play an important role for hop aroma because they produce a fruity smell [21]. Notably, the presence of \(\beta\)-acid lupulone, a bitter acid of hop cones, was found in all methanol extracts with percentage values ranging from 14.5% to 63.8%. This compound has been reported to have sedative, antiangiogenic, antiinflammatory properties and chemo-preventive effects on human colon cancer and was also evaluated for in vivo antimicrobial activity to inhibit _Clostridium perfringens_[5; 22; 23; 24; 25]; 2-methyl-3-buten-2-ol, a degradation product of lupulone, was detected in CCHe (7.2%), PCje (0.5%) and Tpe (1.0%), and it was also shown to be sedative in mice and antioxidant power [26; 27]. Concentrations of bitter acids can vary within cultivars from year to year. The variation may depend on temperature differences or even on precipitation [28]. Furthermore, since the production of secondary metabolites is also under genetic control, the measured concentrations can be useful for a the partial identification of geographical origins. In fact, European and North American wild hops can be distinguished from each other thanks to the relative quantity of bitter acids [29]. In general, hop extracts have been reported as antioxidant agents and the strongest activity was noted for dried hop methanol extracts [30]. In our study, the antioxidant activity of hop methanol extracts was investigated by DPPH and ABTS assays, and the results were expressed by IC\({}_{50}\) and TEAC values. For all samples, low IC\({}_{50}\) values, which correspond to a high antioxidant potential, were obtained. Slight differences among them were observed: PCJe > TPe > STGe > HLBe > CCHe > PCe > HBKe in DPPH and HLBe > TPe > PCE > PCJe > STGe > HBKe > CCHe in ABTS assays, respectively. The PCJe sample, the hop with the highest antioxidant power (IC\({}_{50}\) of 0.027 mg/mL) among those tested against DPPH, showed the highest content of total flavonoids (22.0 mg QE/g dry hop) and a high amount of total polyphenols content (37.0 mg GAE/g dry hop).