Best Practices for Successful Filtration Prior to Bottling
Last updated: 6/2021
Applies to: Winemakers looking to prevent frustrating wine filtration and bottling day delays.
Bottling is a Critical Control Point
Bottling is typically the last critical control point before wine leaves the control of the producer. It is especially important at this stage to ensure that spoilage microorganisms are completely excluded from the final product. Two major components of this effort are:
- Good pre-bottling filtration practices
- Good bottling day practices to avoid contamination(see Best Practices for Preventing Microbial Contamination During Bottling).
This article will address best practices for pre-bottling filtration.
Filtration is often blamed for ruining the day when media clogs prematurely and halts bottling. High differential pressure and clogging is annoying, but is just evidence of filters doing their job. On the other hand, little to no differential pressure progression is a red flag and indicates wine may be bypassing filtration media due to incorrectly seated cartridges, faulty pressure gauges etc. Let’s take a closer look on how to get it right and how to remove potential filtration stress on bottling day:
TIME YOUR PRE-FILTRATION
Wine bottling lines often have their own sterile filtration (0.45µ) membranes. Even if you have completed a 0.45µ filtration prior to bottling, that is not a guarantee the wine will not foul the bottling filter. This is why it is important to time the last depth filtration appropriately with bottling.
Waiting too long after the last depth filtration pass before going to bottling can give colloids a chance to regroup into long, sticky chains that can prematurely clog bottling filters. We recommend bottling within 24 hours after your crossflow or sheet/lenticular filter (Seitz EK or KS50 at the coarsest). Alternatively, if that timeline isn't possible, place a lenticular filter with the same grade in-line with bottling. For sweet or historically difficult varietals, try to keep that time lapse between depth filter and bottling as short as possible. If you must wait longer, consider filtering through a Seitz EK1.
CONFIRM FILTERABILITY INDEX (FI)
Where possible, test for Modified Filterability Index (FIm = (T600 – T200) – 2(T400 – T200))by using the same media (porosity, type and brand of membrane) as you will use to complete your bottling filtration. This should be done as close as possible to bottling. It is always helpful if it is accessible to you, but especially important if you suspect that you might be dealing with colloidal material that could prematurely foul your membranes during bottling.
TIME YOUR ADDITIONS
The following steps if completed after the final depth filtration may result in filterability failure by clogging bottling cartridges and could only be solved by re-filtering:
- Gum arabic
Carefully read the instructions on gum arabic, tannin, mannoproteins, and CMC products – some of them are added 48 hours before bottling, though in that time other colloids may have reformed resulting in filterability failure. If you add anything to change the colloidal status of your wine, you need to retest filterability index to confirm or refilter preventatively.
ADJUST FILTERABILITY IN-LINE
Instead of re-filtering through sheets or crossflow, you can place a lenticular filter that is properly sized to keep up with your bottling line speed in-line. Lenticular filters are sized to comfortably handle an average of 45gpm (16” 4 high EK Supradisc II) and up to 120gpm (Suprapak 6-high) flow rates in a compact footprint. This method of preventative prefiltration results in very high total efficiencies with bottling filters. Mobile bottlers may not allow this extra step in-line to bottling so it can be done into to a holding tank immediately preceding bottling.
USE PRE-FILTER CARTRIDGES
Apart from adding a lenticular to adjust filterability, it is good practice to have a permanent pre-membrane cartridge set up to protect the final filters and improve total throughput and efficiency. If your filterability test barely passed, the proper pre-filter cartridge media choice can gently adjust some of those associative colloids that tend to become dislodged, particularly during crossflow filtration.
STORE FILTER MEDIA PROPERLY
If reusing cartridges and/or lenticular modules that have been stored in an acidified sulfur or ethanol solution (inexpensive vodka), inspect them, then clean and sanitize in place before use. Replace O-rings if you forgot to take them off before storage as they may be stretched out or cracked. Confirm the integrity on the final membranes, right before and after production. For more information on how to store filter media, see "How to Store Lenticular Modules Between Uses" and "How to Store Cartridge Filters Between Uses"