By: Tom Payette, Winemaking Consultant
During harvest, the winemaking staff will often cold settle the juices for white wine making and potentially for cold pressed reds to be made into a blush/Rose style wine. Many smaller wineries may collect the sludgy bottoms of the tank and try to ferment them unsuccessfully. Others will simply allow the bottoms to go down the drain. Both approaches result in an immediate financial loss to the winery either through quality or juice volume loss.
Another approach through the use of a lees filter press unit will allow for the recapturing of these “bottoms” off their rackings and allow these juices to be fermented into a very desirable wine. The lees filter press units have often been said to pay for themselves in the first two to three years if used properly. This may happen sooner depending on the size of the winery and the ratio of red to white wine production for a particular winery.
Financial Impact Example
If a winery presses 40 tons of white grapes per year one could expect the following depending on the variety of white grapes and their average yields. Forty tons may result in approximately 6900 gallons of juice. After cold settling for approximately 24 hours, the winemaker may rack off 6600 gallons with a potential loss of nearly 300 gallons. The 300 gallons left over may actually result in 250 gallons of clean juice after filtering through the lees filter press. This may, after normal winemaking losses, result in a 1200 bottle recapturing of wine from potential waste and that, represented in dollars at an average $10.00/bottle return, is $12,000.00. Soon this non-glamorous and down right dirty operation becomes of interest! Not to mention the wines usually ferment out very nicely – sometimes better than the clear racked juice ! The above calculations are financially conservative and an average. Results may vary depending on many juice components such as pectin, pH, temperature and solids content from the crush pad equipment. The individual winery tank sizes and configurations may also affect these numbers.
Setting up the Filter
It is always recommended to follow the directions that come with the unit when possible. Please refer to these first as your primary source of information. If directions are unavailable, use the guideline below to get started.
1. Back off the screw portion on the lees filter press to open the gap for access to the filter plates.
2. Carefully examine the filter plate cloths (canvases) and look for abnormalities such as rips, tears or creases. Do all the cloths look the same?
3. Examine the filter plates and make sure an understanding is established on the unit’s juice flow inside the filter. Make sure all the plates line up properly and that the end plates are positioned properly at the ends. Does the plate configuration align with the fixed plates on the filter ends?
4. Determine where the juice goes into the filter and how it exits.
5. Close the unit and pressurize to the normal or recommended pressure making sure all the plates are firmly held into place. Check that the canvases are not pinched or creased possibly creating a leak when filtration begins.
This process is very easy once one gets the hang of it. At first the winemaking staff may look at the process in disbelief that another operation will take place during crush. After time, it is a fun rewarding process and many can master ways to reduce the mess greatly. Using this step by step operation will become a template for helping this process along toward success.
Set up the lees filter properly and according to the instructions if they were provided. If not – study the piece of equipment to understand how it works (see above). The overall process summary is that the sludge juice is mixed with DE (diatomaceous earth) and under large pressure forced through canvas filter covers. The canvas will hold back the DE and dirty juice mix sludge and will ultimately become the filter matrix.
1. Perform a clean racking on a white wine juice after cold settling with enzymes and SO2 only. One may use other fining agents potentially at this step. The main agent not to use is bentonite. Bentonite will scertainly throw off the lees filter process and lead toward major frustrations and filtration failure.
2. Collect the racking bottoms in another tank or leave them in the same tank if one can perform the rest of the procedure properly in the tank in which the juice was initially collected.
3. Measure and record this volume of juice settling bottoms for internal and TTB recording purposes.
4. Be able to continuously mix these juice bottoms with a guth style mixer or with a food grade plastic shovel. (For time reasons the author recommends a guth style mixer in the racking valve of the tank)
5. Add 50 pounds of 545 DE per 1000 liters (264 gallons) of juice bottoms and continue to mix. (Please investigate DE and its potential hazardous conditions before using this product and remember to wear all safety equipment necessary. This product may be hazardous to your health. Consult your onsite Materials Safety Data Sheets)
6. While mixing continuously attach a hose to the lees filter press inlet from the bottom valve of the “sludge tank”.
7. Open the valve and allow the juice DE mix to flow to the unit inlet.
8. Start the operation of the unit with the plates well sealed together at the proper recommended hydraulic pressures.
9. Have a piece of hose lead into another tank or bucket to catch the first amount of filtrate that comes through. This is often very dirty at the beginning of the operation. The winemaker may return this juice to the sludge tank to eventually be filtered again. (This amount is often less than 10-15 gallons depending on the unit, juice and the operator)
10. Once the filtrate is “clean” start to capture that juice in another tank. Record volumes as needed.
11. Continue to monitor the process by checking on the unit from time to time. Listen to the unit as a rhythm will be established and one can watch the unit out of the corner of his or her eye.
12. The pressure build-up will progress over time and the unit pump will engage with larger time intervals in-between. This is a sign the unit filtration is clogging and the unit may need to be re-established removing the cakes formed. The flow rate will slow and become an unproductive process.
Important note: Keep an eye on the operation and the mixer. As the juice/DE mix nears the racking valve (typical mixer location), turn the unit off to avoid mixing to a “froth”. At this point substitute with mixing by hand using a food grade shovel or similar action.
Stopping the Unit
1. When to stop the unit is a judgment call. This can be in-between pressloads from the crush pad or other operations of the normal winery day.
2. Turn off the machine.
3. Unplug the unit (optional but recommended).
4. Immediately shut the valve at the receiving tank.
5. Immediately shut off the valve at the sludge bottoms tank.
6. Drain off any clear juice and place in the filtered juice tank.
7. Depressurize the unit if drawing off any clear juice did not perform this operation already.
8. Release the hydraulic pressure cylinder and back the filter plates off one by one.
9. While moving the plates backward, try to remove the solid “cakes” of DE and solids from in-between the canvases. These may remove easily if the process went well and the ratio of DE to juice mix was formulated properly. If a slimy cake developes – change the DE to juice mix ratio.
10. Once all of the cakes have been removed rinse the unit, the canvases, all interior and exterior portions and reassemble the press to start again.
11. Plug the unit back in, open valves as necessary to restart the unit and restart the unit. Remember to catch the first filtrate since this may not be as clear as desired and return to the unfiltered tank sludge bottoms.
Multiple lots: During harvest the winemaker may find the tank space crunch and the speed of the fruit coming in the winery door may necessitate blending of pre-fermented juices. This can been done with success: however, strict records need to be kept to be able to track certain lots, with chemical data, so adjustments can be made to each juice and its contribution to the blend. Juices have been stored with success, as well, during the early stages of harvest for a couple of days. If the winemaker presses 4 tons on one day and more fruit is expected in the next two days, the winemaker may chill the juice bottoms collected, potentially add additional sulfur dioxide, and store the juices until a large enough run has been gathered to justify starting the lees filter press operation. Collect all volume data before and after operation to be able to report all blending activity.
Reducing the Mess
Every winery layout and lees filter will vary significantly. Try, however, to locate your lees filter press close to an electrical outlet that will run the unit and close to your raw materials such as DE, sludge bottoms (or a permanently designated “sludge bottoms” tank) and crush pad. The lees filter press should be located in an area near a drain and water source so hosing down the unit will be convenient and reduce the mess. Place the filter where the blow-by rinse water will not land on electrical plugs or other areas and equipment that may be difficult to clean afterwards. Use warm or hot water since this will help greatly to neutralize and dissolve the sugars of the juice from the equipment and canvases. If possible try to capture the “cakes” of DE as they fall off the filter plates after disassembling the lees filter. This can be done with a bin or tub. Otherwise shoveling may be needed.
One does not need to clean the unit immaculately in between cycles or setups in one particular day. More of a gross cleaning will suffice to set the unit back up and get rolling again.
Some of the Downfalls of a Lees Filter Press
If a great understanding of how the unit works is not established the unit can become a great source of bad cross-contamination. The units are easy to clean but one must make sure to flush out areas such as the piston pumps, surge tanks, inlet centers, sample valves, canvas sheets etc. Flush all parts with copious amounts of water. Make certain to store the canvas cloth plates so air may pass between them after cleaning, otherwise a mold/mildew may form.
Store the unit inside when not in use. Do not leave the unit outside for extended periods of time after its use. Sunlight will break down the canvases and they will need to be replaced sooner than normally expected. This goes beyond the normal problems associated with storing any electrical equipment outside.
Space: These units are usually large size in order for them to do their job properly. They take up large amounts of space when not in operation.
The lees filter press is a very rewarding operation to the winemaker and the financial bottom line of the winery. Once the cellar team integrates this extra operation into their harvest routine it becomes a “piece of cake”. It looks difficult and laborious but it can become extremely easy. Investigate your operation to see if it makes financial sense to add this piece of equipment to your cellar.
Once you add this piece of equipment reward your cellar crew in some form or fashion to recognize them and say: Thanks for helping our business succeed!