## 2 Results
### Aroma Compounds Retention
Cont.} & \multicolumn{1}{c}{} \\ \hline
**Compound** & **W** & **N1** & **N2** & **N3** & **N4** & **N5** & **N6** & **N7** & **N8** \\ \hline \(\sum\)**Festers (mg/L)** & \(1.83\pm 0.06\)\({}^{\rm h}\) & \(1.77\pm 0.07\)\({}^{\rm h}\) & \(2.03\pm 0.08\)\({}^{\rm s}\) & \(2.27\pm 0.06\)\({}^{\rm d}\) & \(2.59\pm 0.11\)\({}^{\rm s}\) & \(1.59\pm 0.02\)\({}^{\rm h}\) & \(1.88\pm 0.02\)\({}^{\rm h}\) & \(2.02\pm 0.09\)\({}^{\rm s}\) & \(2.28\pm 0.03\)\({}^{\rm d}\) \\ \hline Ethyl hexanoate (ug/L) & \(66.7\pm 2.4  
The rest of identified acids had higher concentrations in the reentate than in the initial wine, but the processing parameters did not affect each compound the same way. Octanoic, decanoic and myristic acid concentrations followed the above-mentioned trend: higher pressure leads to higher retention, with slight decrease when cooling was not applied. Their concentrations (in initial wine were 25.6, 65.4 and 24.8 \(\mathrm{\SIUnitSymbolMicro g}\)/L, respectively) increased during wine concentration by reverse osmosis and nanofiltration, especially at 5.5 MPa with cooling where the highest concentrations were found. Pressure increase resulted in higher retention of lauric acid at both processes, but concentrations were slightly higher at regime without cooling in comparison to the one with cooling. Reverse osmosis was more favourable for palmitic acid concentration comparing to the nanofiltration process. The initial concentration in wine (14.0 \(\mathrm{\SIUnitSymbolMicro g}\)/L), in NF retenates decreased by 50% or more (the lowest concentration was found in NF retenate at 2.5 and 3.5 MPa without cooling, 5.2 and 5.3 \(\mathrm{\SIUnitSymbolMicro g}\)/L, respectively). The highest concentration of palmitic acid was found in RO retenate at 5.5 MPa with cooling (38.9 \(\mathrm{\SIUnitSymbolMicro g}\)/L). Nonanoic acid was identified only in RO retenates and it was not detected in initial wine and NF retenates. It is possible that the concentration of nonanoic acid in initial wine was under the threshold of detection for the applied GC/MS method, but its concentration increased during reverse osmosis process. The content of nonanoic acid increased with the higher pressure (the highest concentration was found in RO retenate at 5.5 MPa with cooling, 16.0 \(\mathrm{\SIUnitSymbolMicro g}\)/L). Slight decrease of concentration of this acid was noticed when cooling was not applied comparing to the regime with cooling. In Tables 4 and 5 the sum of concentrations for each group of volatiles (acids, alcohols, carbonyl compounds, terpenes, esters and phenols) was calculated. According to the total sum of all acids in samples, a decrease of acids concentrations was observed in retenates comparing to the initial wine (828.8 \(\mathrm{\SIUnitSymbolMicro g}\)/L), except for RO retenates obtained at 4.5 and 5.5 MPa with cooling and 5.5 MPa without cooling. Lower concentrations of total acids after RO and NF wine treatment were a result of membranes permeability to acetic acid, which had the largest share among acids (82.3% in initial wine). Among nine identified higher alcohols (isoamyl alcohol, 1-butanol, 2,3-butanediol, 1-hexanol, methionol, benzyl alcohol, 1-octanol, 2-phenylethanol and dodecanol), in initial wine isoamyl alcohol (3.98 mg/L), 2-phenylethanol (1.86 mg/L) and 1-butanol (1.06 mg/L) had the highest concentrations. The concentration of 2,3-butanediol was 0.30 mg/L and the concentrations of the rest of alcohols were below 0.05 mg/L in initial wine. An increase of these concentrations was observed in retenates obtained by reverse osmosis and nanofiltration with cooling, especially at 4.5 and 5.5 MPa. However, regime without cooling resulted in a significant loss in higher alcohol content, with the lowest concentrations measured at 2.5 MPa. In the RO retenate at 2.5 MPa without cooling, 1-butanol and 1-hexanol were not detected. Benzyl alcohol was not detected in RO retenates obtained at the regime without cooling regardless the applied pressure, and it was not detected in any NF retenate.