# Using Hydrofluorocarbon Extracts of Hop in a Pilot Scale Brewing Process
## 3 Results and Discussion  
Hop Extraction Using HFC System  
The overall content of \(\alpha\)-acids in pellets, CO\({}_{2}\) extract, and HFC extract resulted to be equal to 0.234 g/g pellets, 0.513 g/g CO2 extract, and 0.597 g/g HFC extract, respectively, as previously reported in Table 2. In Figure 2, the recovery efficiency of hop extracts, evaluated during extraction runs of 180 min with the HFC system, is reported. As shown in Figure 2, a rapid increase in the extraction yield was observed during the first 20 min of process followed by a slightly decreasing trend for the extraction rate and the achievement of a maximum extract recovery of approximately 19% after 120 min of process. The extraction system used in this work allowed operation at moderate temperature and pressure conditions (9 bar, 35 \({}^{\circ}\)C) and provided extraction performances higher than those reported by some authors in the literature by sc-CO\({}_{2}\) techniques. In [PERSON] et al. [27], hop extraction was carried out using sc-CO\({}_{2}\) and extraction yields of 9.79% and 13.65% were reached by an operating temperature of 40 \({}^{\circ}\)C and pressures of 15 MPa and 30 MPa, respectively, in 150 min of process. Furthermore, [PERSON] et al. [28] reported even lower yield values: a recovery of approximately 3% was obtained after an extraction time of 250 min, through two different extraction techniques: sc-CO\({}_{2}\) extraction with and without using ethanol as co-solvent, and cyclically pressurized solid-liquid extraction performed by a Naviglio extractor [29]. The maximum \(\alpha\)-acid yield obtained in this work through the innovative HFC extraction system (approximately 50.5%) was comparable with the maximum efficiency of 50.7% reached by [PERSON] et al. [30] using sc-CO\({}_{2}\) at 150 bar and 20 \({}^{\circ}\)C. Moreover, higher yields were obtained only by stronger pressures with different solvents at various densities, such as propane, sulfur hexafluoride, and dimethyl ether. Furthermore, comparable extraction yields in \(\alpha\)-acids were obtained by [PERSON] et al. [31], which carried out a pulsed-field extraction treatment on methanolic hop extracts. Additionally, in this case, HFC technology results in a less complex and expensive technique in addition to ensuring a final solvent-free extract. As shown in Figure 3, the \(\alpha\)-acids concentration profile, c\({}_{\alpha\text{-acids}}\), found in samples progressively collected during the process time, remained approximately constant (about  
Figure 2: Extraction yield of hop extracts (n\({}_{\text{e}}\)) evaluated during the extraction process carried out using Noroflurane solvent. \(0.6\) g/g\({}_{\text{extract}}\)). As the extraction proceeded, hop extracts equally concentrated in \(\alpha\)-acids were obtained due to their similar extraction kinetics. Figure 4 shows a comparison between the isomerization performances obtained with hop pellets, sc-CO\({}_{2}\) extract, and HFC extract during lab-scale isomerization trials II, I2, and I3, respectively. Pellets and CO\({}_{2}\) extract showed an initial iso-\(\alpha\)-acid concentration equal to approximately 10 mg/L while HFC extract contained a negligible initial iso-\(\alpha\)-acid amount. Despite this, HFC extract provided a higher isomerization rate during boiling than that observed using CO\({}_{2}\) extract. Furthermore, both CO\({}_{2}\) and HFC extracts showed a higher final iso-\(\alpha\)-acid content than that reached using pellets after 50 min. During the first 15 min of process, a higher increase in total iso-\(\alpha\)-acids concentration (ciso-\(\alpha\)-acids) was observed when pellets and CO\({}_{2}\) extracts were added into the boiling word (trials I1 and I2, respectively) in comparison with the iso-\(\alpha\)-acid amount determined by adding HFC extract. However, for longer times, HFC extract provided the highest production rate of iso- \(\alpha\)-acids, with a final concentration of 47.550 \(\pm\) 0.637 mg/L, reached after 35 min of boiling process.