6.1.1.b Different filterability measurements for a wine

Clogging index (CI)

The Clogging index is a standard test used to measure filterability, but it can only be used for final filtration on a wine with a low turbidity (NTU<3). A membrane filter of 0.65 µm and 25mm diameter must be used. This index does not enable anticipation of a wine's preparation prior to its final filtration.

Clogging index interpretation (millipore 0.65 µm) (Source: Romat H., 2014. Filtration en œnologie. Féret Bordeaux Editions.) :

Maximum filterable volume (Vmax)

The Vmax is the maximum theoretical volume that can be filtered within a given time frame for a given filter. It is calculated based on the same filter as the CI, i.e. a 0.65 µm membrane filter. It does not enable an understanding of the filtration process as a whole, or the orientation of post-fermentation clarification operations to achieve optimal filterability. However, it does enable an assessment of the need to renew cartridges during bottling, by calculating filtration quality losses at each cleaning and taking into account the Vmax of each wine.
Interpretation of the maximum filterable volume (Source: Romat H., 2014. Filtration en œnologie. Féret Bordeaux Editions.):

Clogging factor (CF)

Since the filterability index (FI) and Vmax measurements can only be calculated for very low turbidity wines (NTU<3) and using a single filter medium (0.65 µm), a Clogging factor was created to measure the filterability of less clarified wines (NTU>50). This coefficient works for any type of frontal filtration and helps anticipate clarification and filtration operations before final filtration for bottling. The lower the coefficient, the slower the clogging process. Conversely, the higher the coefficient, the faster clogging will occur.

Interpretation of the clogging factor (Source: Romat H., 2014. Filtration en oenologie. Féret Bordeaux Editions.):

Lamothe-Abiet Filterability Criteria (LAFC)

The LAFC defines a wine's filterability, regardless of its condition and turbidity. This measurement can therefore be carried out on a wine during the ageing process. The filtration membrane must be suited to the turbidity of the wine to be filtered, as with the CF calculation.
The protocol consists of filtering a sample of wine under constant pressure for 2 minutes and noting the volume filtered every 10 seconds during these 2 minutes. The final score varies between 0 and 200. The lower the LAFC, the better the filterability and the less likely it is that clogging will occur.

Interpretation of Lamothe and Abiet filtration criteria (Source: Romat H., 2014. Filtration en œnologie. Éditions Féret Bordeaux):

Good practice during monitoring

In the case of wines that have previously been difficult to filter, the wine should be monitored following the completion of malolactic fermentation to determine whether or not clarification is necessary. The tests should ideally be repeated following each racking, in order to follow the wine's evolution as accurately as possible. If filtration has not been a problem in the past, the filterability measurements can be carried out later, with the initial measurement being taken during fining.

The filtration temperature should ideally be identical to the temperature used for the filterability tests because it is a parameter that can affect viscosity and therefore the wine's filterability. For example, a wine's filterability can be reduced when the temperature is colder during the final filtration (before bottling) than during the tests. This parameter is particularly significant in the production of sweet wines.