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

showed also that 2 mg/L of oxygen moreover on white wines involved significant sensory
modifications after a few months (Berta et etc., 2000; Boulet, Vidal, 1999). Therefore, various
studies undertaken to characterize the appearance of dissolved oxygen during operations
performed on wines show that bottling is one of the most critical phases (Vidal et etc., 2004;
Castellari et etc., 2004), especially as once the bottles have been sealed, the only remaining
means for mastering the evolution of wines are the storage parameters (closure permeability,
temperature, relative humidity, light, etc.).
On one side, the presence of O 2 in the wines, following its dissolution, is not a stable state in
time. Dissolved oxygen is gradually consumed by various substrates, mainly polyphenols
(Singleton et etc., 1979). The disappearance of floral flavours is faster under the effect of
oxygen additions even at 15°C and at the organoleptic level, aromatic deteriorations arrive
before chromatic deteriorations (Escudero et etc., 2002).
On the other side, CO 2 is produced in a large quantity by yeasts (81 g/L for wine of 10%
vol.) and lactic acid bacteria (1.6 g/L for 5 g/L of malic acid) during alcoholic and malolactic
fermentations. During storage and various treatments of the wine, the carbon dioxide content
tends to decrease because of the tendency to equilibrate the CO 2 partial pressure of the wine
with the atmospheric partial pressure. Finally variable quantities remain at the time of the
bottling. However the carbonic gas plays a key role in the organoleptic characters of the
wines, even if its content is lower than its perception threshold (500 mg/L). Thus adjusting the
carbon dioxide content of wines has a great importance from the sensorial point of view. The
CO 2 content in bottled wines will have to be adjusted approximately to 300 mg/L for the red
wines for ageing and up to 800-1800 mg/L for the white and rosé wines.
Already used in waters, beverages and effluents treatments, membrane contactors present a
great interest in oenology because this new technology enables implementing liquid-liquid,
liquid-gas or liquid-gas-liquid separations. The main component of the system is a
hydrophobic porous membrane system. Only gases with low molecular weight like O 2 and
CO 2 can pass through this barrier. It is possible to reduce dissolved gases (eg CO 2 , O 2 ) or to
add for example CO 2 in wines before conditioning in bottles or in bag-in box.
After a presentation of this new technology and of the manual membrane contactor used,
this study describes the first results obtained by INRA experimental unit of Pech-Rouge
(France) for the management of dissolved gases of still wines. The main aim of these trials
was to reduce the dissolved oxygen content to a level lower than 0.5 mg/L in order to increase
the shelf life of the wines. At the same time, the dissolved carbon dioxide content is adjusted
to a level between 300 and 1800 mg/L according to the type and the style of the wine for
sensorial reasons.
MATERIALS AND METHODS
WineBrane ® membrane contactor:
The WineBrane ® skit (INOXPA patent pending) consists of one or several membrane
contactors in the way, that when connected with the operation and secondary medium,
multiple treating processes are possible. The power spectrum of the plant covers flow rates
between 1000 and 20000 litres of wine per hour for the gas management (Schmidt et etc.,
2010).
The design and construction of the units is performed in compliance with the requirements
of the food-processing industry. The membrane material is polypropylene and it has FDA
approval.
The design is CIP cleanable (alkaline solution and disinfectants), units can also be sanitised
with hot water.