## 2 Results
### Aroma Compounds Retention
Methionol was found in each RO retenate, with the highest concentration at 5.5 MPa with cooling (32.3 \(\mathrm{\SIUnitSymbolMicro g}\)/L). However, only two NF retenate (at 2.5 and 3.5 MPa with cooling) contained methionol and the concentrations were lower than in initial wine, 20.6 \(\mathrm{\SIUnitSymbolMicro g}\)/L. Nanofiltration membranes showed lower ability to retain higher alcohols comparing to the reverse osmosis ones according to the total amount of alcohols. This was mostly visible when cooling was applied. Without cooling regime and higher temperatures resulted in a significant loss of alcohols during both processes. Regarding the influence of applied pressure and temperature on retention, carbonyl compounds (4-propylbenzaldehyde, geranyl acetone, lily aldehyde and hexyl cinnamaldehyde) and terpenes (\(\alpha\)-terpinolene, nerol, \(\beta\)-citronello, \(\beta\)-damascenone and phenanthrene) concentrations followed a similar trend as higher alcohols. The highest concentrations of these compounds were found in retenates obtained by reverse osmosis at 4.5 and 5.5 MPa with cooling. Significant loss of most carbonyl compounds and terpenes was observed with the regime without cooling comparing to the regime with cooling. The highest increase was noticed for 4-propylbenzaldehyde whose concentration increased from 6.7 \(\mathrm{\SIUnitSymbolMicro g}\)/L in initial wine to 124.9 \(\mathrm{\SIUnitSymbolMicro g}\)/L in the RO retenate at 5.5 MPa with cooling, and only 25.5 \(\mathrm{\SIUnitSymbolMicro g}\)/Lin the NF reentate at 5.5 MPa with cooling. In NF retentates, absence of cooling had less impact on several carbonyl compounds and terpen retention than transmembrane pressure. The retention of 4-propylbenzamidealdehyde, lily aldehyde, hexyl cinnamaldehyde and \(\beta\)-damascenone was higher when cooling was not applied in the NF retentates than in the ones obtained with cooling. Temperature increase had low influence on the concentrations of lilly aldehyde and \(\beta\)-damascenone during RO process at 4.5 and 5.5 MPa (there was no significant difference between two temperature regimes at those pressures). The total concentrations of carbonyl compounds (20.9 \(\mathrm{\SIUnitSymbolMicro}\)/L) and terpen (69.4 \(\mathrm{\SIUnitSymbolMicro}\)/L) in initial wine increased during RO and NF processes. RO membranes retained higher concentrations of carbonyl compounds and terpenes than initial wine, with the highest total concentrations obtained at 5.5 MPa with cooling (173.2 and 211.5 \(\mathrm{\SIUnitSymbolMicro}\)/L, respectively). Esters were the largest group with 19 identified compounds. In initial wine, diethyl succinate had the highest concentration (0.73 mg/L), followed by ethyl octanoate (210.7 \(\mathrm{\SIUnitSymbolMicro}\)/L), ethyl hydrogen succinate (183.0 \(\mathrm{\SIUnitSymbolMicro}\)/L), ethyl palmitate (107.5 \(\mathrm{\SIUnitSymbolMicro}\)/L) and diisobutyl phthalate (103.4 \(\mathrm{\SIUnitSymbolMicro}\)/L). The reverse osmosis process with cooling resulted in an increase of concentrations of most esters, where the retention was greater at higher pressures (4.5 and 5.5 MPa). The increase of temperature resulted in a decrease of ester content, but the increase of pressure at regime without cooling had different effect on individual esters. The concentrations of ethyl 4-hydroxybutanoate, ethyl octanoate, ethyl pentadecanoate and ethyl linoleate decreased when higher pressure was applied at regime without cooling. There was no significant difference in concentrations of ethyl vanillate, ethyl laurate and ethyl stearate among RO retentates obtained without cooling at all pressures, while the pressure increment resulted in higher retention of the rest of esters. During nanofiltration process, the retention of esters was also greater at higher pressures (4.5 and 5.5 MPa) and lower temperatures (regime with cooling). The concentrations of ethyl 4-hydroxybutanoate, ethyl pentadecanoate, ethyl oleate and ethyl stearate decreased as the pressure increased when cooling was not applied.