by Jon M. Casey
For wine makers, the need for filtration equipment is a given. In order to produce a bottle of clear, good tasting wine, somewhere along the winemaking process, the batch needs to be filtered. That’s where the decision-making process begins. Should the filter be a cartridge filter? Should it be a filter press? Or, will a lenticular filter or a Cross-flow filter design be the best choice? The options are many.
In a joint enology series presentation on Lenticular and Cross-flow filtration, Maria Peterson of Scott Labs, Hans-Joachim Schulze of CMF Consulting and Jerry Forest of Buckingham Valley Vineyards and Winery in Buckingham, PA, teamed up to offer application and management tips on how to use these two, sophisticated yet easy to use filtration methods. The session was presented at the 2016 Eastern Winery Exposition in Lancaster, PA.
Maria Peterson began by highlighting some of the management tips she has learned over the years working with lenticular filters. Peterson explained that in appearance, the lenticular filter looks a lot like a fat version of a cartridge filter. Unlike a cartridge filter however, the lenticular filter’s media is a series of filtration modules rather than a cartridge of some kind. Like other filters, the lenticular filter can be equipped with various filter media materials, but the best, more serviceable filter media is a material that can be easily backwashed at intervals during the filtering process and then cleaned and stored for future use.
Peterson explained how a filter of this type could be a helpful choice, especially for smaller, beginning wineries. While this size of filter is ideal for smaller batches, they also can be large enough to accommodate future growth over time. She recommended that the operator consider where they plan to be in five years and make their buying decision based on this projected growth rather than what the immediate need might be. Since a lenticular filter’s modules can be stacked to increase the total filtration capacity, the unit would not become undersized as the winery grows. She noted that the winery might wish to upgrade to a cross-flow filter when a larger filter is needed.
A major benefit of a lenticular filter is its backwashing capabilities. Unlike a filter press where the sheets need regular replacement, the lenticular filter modules are backwashed when the pressure differential between the inflow and outflow increases to no greater than 17 psi. She emphasized the importance of that number as a threshold for backwashing because the filter modules tend to plug at longer usage and when that happens, backwashing becomes difficult and sometimes impossible. Since filter modules cost more than filter sheets, it is not economical to replace them unnecessarily. Overall, with proper backwashing and storage, the overall savings of this method of filtration is a major reason to choose this filter.
Storing the filter modules properly is an equally important step. The filters can be stored over the winter for use in the next season. Care needs to be given when lifting the dome of the filter from the base, not only to protect the modules within, but also to prevent injury to the winemaker. Once the wine making is complete and the filter has been sufficiently backwashed to clean the modules, they may be removed and stored in a vessel like a Rubbermaid plastic tub with a lid. The modules need to be submerged in a sanitizing solution with a pH of 3.5. If the operator is using citric acid as the sanitizing agent, the solution needs to be lower at a pH of 2.0 and 200 ppm of Sulfur dioxide needs to be injected into the solution as well as an antioxidant to prevent bacterial growth over the storage period.
In the second segment of the presentation, Hans-Joachim Schulze of CMF Consulting spoke on the attributes of cross-flow filtration as a “one-step” method of filtering out the turbidity, producing a clear, bottle-ready product. He said it is a virtually no-mess filter. Similar in appearance to a commercial reverse osmosis filtration system, a typical filtration system would contain a pre-filter ahead of a booster pump that introduces the unfiltered wine into the system. A circulation pump moves the liquid along the length of the filtration media, in this case, a CMF Module containing a Hollowfiber membrane. As the wine passes along the membrane, filtered wine passes through the membrane and flows to a filtered wine containment vessel. From there, it is ready for bottling.
Schulze said the cross-flow filter outperforms a centrifuge for removing particulates because of the absence of the “battering effect” that a centrifuge tends to exert on the large particles in the wine, which increases the amount of colloids in the wine. Increased colloids tend to complicate filtration. By removing the particles under lower pressure, the filtration is more complete. He said that before filtering with a cross-flow filter, the wine should undergo at least one racking.
According to Schulze, “In order to produce a technically successful filtration of wine, the wine must be free of fining agents such as PVPP, gum Arabic, gelatin, protein and other sticky substances that may splint the membranes in the filter. The NTU value of the wine to be filtered may not exceed 100. In individual cases, wines with more than 100 NTU can be filtered; however, that increases the frequency of cleanings.”
Schulze said that when a wine contains higher levels of Polysaccharides, cleaning with suitable enzymes is important. “Polysaccharide structures on membranes can only be removed by enzymatic and chemical cleaners and do not respond to clear water rinses.”
He concluded by saying that there is more than one method for backwashing the systems, depending on manufacturer. Some systems use a gas pressure backwashing process while other brands rely upon pumps. He preferred the pump method over the gas design because the filtrate to be removed stays on the same side of the membrane during the cleaning process while the gas pressure forces the filtrate through the membrane.
Irrespective of brand or design, Schulze said that all cross-flow filters must be cleaned on schedule and not when the winemaker has the time or inclination to do so. When cleaning the filter, it must be cleaned completely. Inadequate cleaning will lead to serious quality problems. Following the manufacturer’s specific instructions is imperative. The manufacturer will know the best methods for cleaning to provide optimum performance. While the cross-flow filter is a sensitive tool, it can make winemaking a simpler process.
Concluding the filter presentation, Jerry Forest, owner-operator of Buckingham Valley Vineyards and Winery, Buckingham, PA, said that his winery has been using a cross-flow filter since 1989. He said he went to Germany to see one being used at a winery there and immediately saw the value of owning one.
They started with a 2-cartridge unit and today; they are on their fourth cross-flow filter system.
Forest said they have been in business since 1966 and that over time; they have used virtually every method of filtration, everything from cartridge filters to centrifuges. Cross-flow filtration is their choice for today. This method has been used in the food industry since the early 1960s but did not become useful in wine making until the 1980’s after certain wine making operational issues were resolved.
Forest said the cross-flow system is simple to operate. The unit does not need tending, so the winemaker can do other work besides watching the filtering process. Since they produce between 30,000 and 35,000 gallons per year, this is a cost-effective way to filter the wine. “It is a single-pass filtration,” he said. “We can take a wine that is somewhat cloudy, pass it through the filter [and it is ready to bottle].”
He said they are easy to maintain since there are no filter pads to dispose off. More importantly, there is very little waste. On an average, they lose three gallons per run. Their three-cartridge filter will run 300 to 500 gallons per hour.
Having used this type of filter for more than two decades, Foster said the improvements over time have remedied the problems that were typical in the early years. He said pectins are not friendly to a cross-flow filter and that fining can be a problem. The filter can filter the wine, but it is the buildup from the fines that can reduce performance. Racking the wine cleanly helps improve that condition. He emphasized that a cross-flow filter is not a sludge filter, so it is important to use it as it was designed. “In 25 years, I’ve never plugged a cross-flow filter module that I could not unplug. They are very resilient,” he said. “It works better on wines that have been settled.”
In closing, Forest said that while he has had improved and larger models at his winery over time, his original unit is still in operation in another state. From his experience, the longevity and durability of a cross-flow filter is evident. With proper care and maintenance, the lifespan of the units are not an issue. Cartridges may require replacement, but that is not typical. He said as far as he’s concerned the value of owning one is “priceless.” “I cannot imagine making wine without it!”
New filter technology helps make wine production more efficient
by Jon M. Casey