exact management of dissolved gases of wines by ... - Oiv2010.ge

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Operating modes of WineBrane 2500: VACUUM mode: the use of vacuum lower than 100 hPa in lumen side reduces O 2 and CO 2 according to their partial gas pressure out of the wine. The gas molecules, which crossed the membrane wall, are then eliminated by the vacuum pump. Thus, vacuum deoxygenizes and decarbonises the wine at the same time. CARBONATION mode: to readjust CO 2 content, it is necessary to carry out a second passage without vacuum but by a CO 2 sweep with low overpressure in lumen side (∆ pressure between lumen side and shell side = 200-300 hPa). A back pressure is applied on the outlet of the gas side, to force CO 2 to pass into the wine. In addition to the two previous modes, INRA carried out two new modes in order to check if it is possible to deoxygenize and adjust the CO 2 content in only one passage in the WineBrane skit. STRIP mode: an inert gas circulation (N 2 , CO 2 or N 2 /CO 2 mixture) in lumen side will make it possible to impoverish the oxygen content of wine by keeping the CO 2 concentration. If CO 2 partial pressure of carrier gas is higher than that of wine, the wine will enrich in CO 2 . In the opposite case, the wine will be impoverished in CO 2 . Roughly, if the carrier gas contains approximately more than 20% of CO 2 , a red wine will enrich in CO 2 (50% for the white and rosé wines). The strip mode is used to increase CO 2 concentration at the same time as to reduce O 2 concentration. If a strong carrier gas flow is introduced, O 2 will be reduced but with a higher carrier gas consumption. COMBO mode: a partial vacuum is coupled to an inert gas flow in lumen side, in order to deoxygenise the wine and to adjust its CO 2 content. The combo mode is used when the aim is to keep CO 2 concentration at the same time as to reduce O 2 concentration. This mode is more efficient for deoxygenating at constant CO 2 level because the carrier gas consumption is lower than with strip mode at same deoxygenation level. Moreover, carrier gas consumption (CO 2 ) in the combo mode is more important than in strip mode to increase CO 2 content of the wine. And the strip mode is more efficient than combo mode when wine needs a strong carbonation (when initial CO 2 is much lower than target CO 2 ) at the same time as a deoxygenation. Methods of Analysis for gaseous molecules: Oxygen control at inlet and outlet side of the apparatus was carried out by PreSens luminescent probe and PSt3 luminescent spots glued onto inner surface of the sight glass “Figure 3”. A PreSens Fibox 3 trace fiber optic probe was used. The Fibox 3 measures the luminescence decay time of an immobilized luminophore. The luminophore is excited with a sinusoidal intensity-modulated monochromatic light delivered by an optical fibre and its decay time causes a time delay in the light signal emitted by the luminophore. This decay time, or phase angle, Φ, decreases in the presence of oxygen and is correlated to oxygen content. The PSt3 sensor selected to perform this study can be used for a broad range of oxygen concentration ranging from 0 to 50 %.
Figure 3: PreSens system with its optical fibre and its PSt3 spot glued in a sight glass. CO 2 control was carried out by Carbodoseur to the sample taps located at inlet and outlet side of the apparatus. GC analyses of higher alcohols and esters of wine (headspace sampler coupled to GC Agilent 6850) were performed on samples taken at inlet and outlet side of the apparatus. RESULTS AND DISCUSSION The wines used (75% of white or rosé, 25% of reds) were micro filtered before treatment. All treatments were carried out from tank to tank by the racking connection valves. The average temperature of the wines was of 23.9 ± 1.8°C, except for 4 batches (< 7°C). The combo and strip modes developed by INRA UEPR allowed in only one passage on WineBrane ® pilot to deoxygenize the wines as well as by the vacuum mode while controlling the CO 2 content “Tab. 1”. The CO 2 content of wines treated by the vacuum strongly decreases. The O 2 content after carbonation is almost stable. Table 1: Summary of treatments of wines carried out by INRA. Average ± standard deviation for the 4 last columns. *For choosing combo, strip or carbonation mode, the final CO 2 content depends on the required CO 2 quantity. The required CO 2 quantity is limited by the temperature and the strip gas CO 2 concentration, according to the abacus of Lonvaud-Fumel, 1976, and also the strip gas mass flow as well as the differential of pressure between Mode Nb of batches Total volume hL lumen and shell side. Initial [O 2 ] mg/L Initial [CO 2 ] mg/L Deoxygenation output % Final [CO 2 ] mg/L Vacuum 10 107 4.25 ± 2.82 500 ± 643 - 88.1 ± 3.3 133 ± 140 Carbonation 3 55 0.56 ± 0.09 315 ± 33 + 4.6 ± 3.2 1425 ± 459 Strip 16 360 0.98 ± 0.32 509 ± 227 - 84.5 ± 4.3 645 ± 297 Combo 19 256 2.28 ± 2.31 446 ± 266 - 87.8 ± 4.5 537 ± 359 For carbonation, strip and combo modes, these first tests showed that consumption of carrier gas is close to 0.5 L CO 2 / L of wine for an addition of 300 mg/L of CO 2 from an initial CO 2 content of 700 mg/L. Moreover, we observed a diminution of the flow on red wines, perhaps because polyphenols constitute a hydrophobic bio film near the membrane. Oenological and volatile compounds analyses: Whatever the used operating process, alcohol percentage, volatile acidity, pH values, free and total SO 2 data and absorbance values at 420, 520 and 620 nm were not modified.
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Page 7: Diban N., Athes V., Bes. M., Soucho

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