Filtration practice in France
Christophe Gerland
INTELL’OENO SARL
c.gerland@tiscali.fr
Filtration is an important step of winemaking in France as in all other parts of the world; filtration is used
more or less during all steps of winemaking: filtration of must, prefiltration of wines on diatomees filters,
filtration on cartouche and finally membrane filtration; more recently introduced, tangential
microfiltration is more and more used at various steps of winemaking.
Not all wines follow the same process and the same type of filtration:
the higher the risk of
microbiological problems, the more tighter is the filtration (smaller pore size). Also, a new tendency is
appearing: non filtered wines. This is linked to the ecological evolution of consumers, and concerns
generally high quality wines (at the bottling). This presentation will discuss the influence of different
types of filtration on chemical and organoleptical composition of French wines.
Impact of (Kieselghur) filtration diatomaceous earth (DE)
It is generally observed that filtration has an impact on chemical composition of wines, but the degree of
impact varies in function of the filtration technique and of the wine. The impact of diatomaceous earth
(DE) filtration depends on the raw material (Tables 1 and 2). On a white wine from Bordeaux (Serrano,
1998), a significant influence is noticed on the total polysaccharides but there is no difference regarding
the fermentative aromas (table 1). On a red wine from the same area (Serrano, 1998), the same effect is
observed on polysaccharides but there is no effect on colour neither on tannins (Table 2).
In both cases, no difference has been observed at tasting.
Impact of membrane filtration
As in the 2 examples exposed here (Table 3), the membrane filtration is generally made after a DE prefiltration on Kieselghur. It can be observed that the impact depends on the wine composition, and can be
absent (case of the Syrah wine) or quite important (Bordeaux wine). In the 2 cases, the organoleptical
profiles of the 2 wines were similar.
Impact of tangential microfiltration
This technique, introduced in enology in the past 10 years, is more and more used, due to its possible
automatization and its ecological benefits (avoiding waste materials). Its influence on color is a little bit
higher than classical Kieselghur filtration, but genrerally low (Table 4). It depends on the wine, on the
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technology and on the membrane type. Its minimizing loss of wine polysaccharides (Moutounet, 2000),
especially with the utilization of frequent backflush. The removal of yeast and bacteria concentration is
very effective (Caoh Thanh, 2003), leading generally to quiet sterile wines. This technique can be
adopted as an alternative of DE filtration, but not replace final membrane filtration. It is used for example
to stop fermentation in sweet wines. In all the trials shown here (Cao Thanh, 2003), no organoleptical
differences was noticed between the wines with and without filtration.
The choice to filter or not to filter
A very interesting study has been made by ITV France and the professional newspaper Bourgogne
Aujourd’hui. 2 cuvées of Beaune 1er cru has been bottling with low or normal SO2 content, with different
degree of filtration or no filtration, and were stored for one year at 12 or 18°C. A tasting was then
organized to judge the quality of those wines. The results (Table 5 and Figure 1) show that the more
important factor is the temperature of storage, which can favor the development of microorganisms. The
wines stored at 12°C show the best comments. One stored at 18°C was rated very bad, the development
of Brettanomyces with production of ethyl-phenol is suspected. It is the one that was not filtered. This
study showed the risk of not filtering wines when the temperature can not be well managed, which is
generally the case after delivery to customer or retailer from the winery.
Conclusion
The different techniques of filtration are more and more efficient and well managed in the winery, their
impact on the composition and the quality of the wines can be very low, especially when the technique
chosen is well adapted to the wine. The actual tendency not to filtrate wine has no evident direct positive
impact on the wine quality, but is also very risky for the evolution of the wine, due to possible
development of microorganisms. Regarding the more frequent apparition of problems like Brettanomyces
type deviations, this choice could be conduced with good management of storage temperature of wines
and with the help of fine microbiological controls. The utilization of fining and also of more important
dosis of SO2 should be adviced in this case.
Bibliography
Cao Thanh B., 2003. Optimisation de la filtration. Rapport interne Inter Rhône.
Garnier C., 2002. Essais de préparation à la mise en bouteille. Rapport interne Chambre d’Agriculture de
la Drôme.
Moutounet M., Vernhet A., 2000. Microfiltration tangentielle des vins. Œnologie Claude Flanzy, p 958.
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Serrano Michel et Paetzold Michael, 1998. Traitement physique des moûts et des vins. J. Inter. Sci.
Vigne et Vins, n° hors série.
Tupinier C., Gerbaux V., 2002. Surprises, verre en main. Bourgogne Aujourd’hui n°50.
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