By: Alyssa L. Ochs
During winemaking, filtration occurs right before bottling to remove any unwanted particles that the winemaker doesn’t want in the finished product. The goal is to create a clear and stable wine that consumers will love, but there are multiple ways to achieve this result.
Choosing the appropriate filtration products and equipment can make a huge difference in how a wine turns out and how closely it adheres to the desired style of the winemaker. It is beneficial to learn about different filtration processes to choose the best methods for various wines.
Overview of Wine Filtration
Wine filtration works by passing the wine through tiny holes–similar to using a coffee filter. The smallest particles and liquid pass through the filter, separating everything else from the wine. The process creates a more stable wine, particularly as filter size is reduced and fewer microbes make it into the finished product.
Not every winemaker chooses to filter wine, and not every wine needs to be filtered. However, there are many reasons to use a filter. Filtering gently polishes wine and gives it a softer finish. It helps a wine be more microbially stable and preserves the integrity of the product. Although it is not a health or safety requirement, most modern and commercial wines are filtered in some way.
Options for Wine Filtration
It’s easy to become overwhelmed by the number of wine filtering options, especially when new to winemaking or making a style of wine for the first time. For example, there’s pad filtration, membrane filtration, earth filtration and reverse osmosis. Other methods include ultrafiltration, crossflow filtration, ceramic membrane crossflow, racking and cold stabilization.
The first step in removing suspended solids is typically using a coarse depth filter. Depth filters catch particles but aren’t effective in removing microorganisms from wine. Next, tighter pad depth filters are used. As a final step, winemakers can use membrane filters to catch microorganisms.
Pad filtration involves running wine across a pad, typically made of cotton, polyethylene or cellulose. Pads typically require a setup with a plate and frame and a pump to move the wine. Filter pads work by having wine flow into the rough side of the pad and then out from the smooth side. Different pads are used for red and white wine, but choosing the right filter pads depends on the total filtering surface area. Although pads are inexpensive, they are designed only for one-time use. There can be high leakage rates and long setup times with pads, too.
Cartridges offer an alternative to pads. They use housings, leak less than pads and are cleaner to work with; however, they are also costlier and require more maintenance. It’s important to store them properly so they last a long time and make the investment worthwhile.
Membrane filtration uses a cartridge made up of nylon, glass fibers, polypropylene or cellulose to facilitate screening techniques. This method is often used for microbial stabilization purposes and is the final step before wine is bottled.
Some winemakers use earth filtration using diatomaceous earth, a soft rock ground into a white powder. DE serves as a coating on filter pads or screens before filtering. This method involves covering a stainless-steel or nylon screen with DE and pouring wine and DE through the screen for filtration. It’s a meticulous process that may require supportive plates, a pump, a rotating drum and a rotary vacuum filter. Respiratory and eye protection are required during use due to health and safety concerns about handling DE. Crossflow and centrifuge filtration offer safer alternatives.
For crossflow filtration, the wine moves with significant force and pressure across a porous membrane. Wine is pumped through a partially enclosed pathway and produces juice with very concentrated particles. There is a high initial investment associated with crossflow filters, including replacement membrane costs, which is why many small and mid-sized wineries don’t use them.
Ultrafiltration is a crossflow method using a membrane with a nominal relative weight cutoff of 10,000 per molecule. Winemakers use this method to enhance the flavor of wine and make it more stable because ultra-filtration gets rid of all sizable particles and proteins.
Ceramic membrane crossflow is an advanced technique that incorporates pressing mechanisms. This technique ensures high levels of clarity and reduces product loss, especially crucial for high-value wines. Durable ceramic membranes can deliver automatic production cycles and keep a winery’s environmental impact low.
Racking is a non-obtrusive way to filter wine and involves moving wine between barrels. This method is only somewhat effective, as some wine remains behind in the bottom of the barrel with the sediment during the manual transfer.
Aside from filtering, cold stabilization is a method used to clarify wine. This method requires the winemaker to deeply chill the wine to remove tartaric acid crystals from the product.
Among the various options available for wine filtration, Heyes Filters’ Xflow System stands out. They manufacture their products in the U.S., simplifying the search for spare parts and support while potentially limiting downtime if service is required. Based in Torrance, California, Heyes Filters specializes in filtration and purification to serve the food, beverage, pharmaceutical and biotech industries.
Mike Laffey, the technical sales engineer for Heyes, told The Grapevine Magazine about two crossflow platforms–fully-automated and semi-automated systems–that the company offers.
“Our fully automated systems are PLC-controlled with pneumatic valves and Auto CIP,” Laffey said. “The fully automated systems can be configured sans CIP depending on the customer’s request. Our crossflow systems can be customized to meet the customer’s needs.
“The Heyes Filters semi-automated systems are designed for lower cost and have manual valving and manual CIP. The semi-auto unit does have an autonomous feature. The operator can set the unit up for filtering and enable the autonomous feature, and the system will monitor itself and shut down either when the tank being filtered is emptied or if the flow rate, due to fouling, drops below a predetermined set point. The crossflow unit will shut down and sit idle with the internal check valves, keeping the filtered wine in the receiving tank from back-flowing through the system.”
However, when operating the Xflow system, avoid sending wine that is not yet ready for this type of technology. “Settling, racking and fining are all typical processes in the winemaking journey, but prepping wine for crossflow filtration does take some additional steps to maximize the efficiency of the filtration process,” Laffey said.
Winemakers should keep their current plate, frame filter and any other filtering equipment even after buying the crossflow unit because these can be useful as pre-filters or to remove TCA from wine.
When Heyes Filters trains winemakers on the initial setup of the Xflow system, the focus is on proper cleaning and maintenance to maximize the filtration process.
“We do this by monitoring the transmembrane pressure, inlet pressure value plus retentate pressure value/permeate pressure value,” Laffey said. “To us, this is the ‘voice’ of the membrane telling you how well it is permeating either during filtration as it rises or during the CIP cycle as it is beginning to lower through the chemical cleaning process. The goal is to keep the system ready for the next filtration run.”
Other troubleshooting tips include monitoring the fouling rate and not running the system too quickly in the beginning. The transmembrane rate should be kept low for as long as possible to allow the membranes to flow and not plug up too fast. Heyes Filters regularly helps customers develop strategies for using fining agents before initiating the crossflow system.
Rochester, New York’s Aftek Filtration Options has over 35 years of filtration expertise. It offers flotation, pad filtration, cartridge filtration, membrane and crossflow options for wineries.
Jim Russell, who handles regional sales for Aftek, said he has seen many wineries that produce less than 25,000 to 40,000 cases using pads during post-fermentation. He highly recommends using membranes for pre-bottling filtration to ensure sterile filtration into packaging.
“The membrane is integrity testable and allows for us to challenge the filter media before and after bottling to ensure stable shelf life. Some of our customers are shifting to crossflow for wine to replace pads, and this is a discussion we have for sizing and timing to make the best use of capital for growth and packaging,” Russell said. “The filtration products we work with our customers on are minimizing any oxygen pick-up and degradation of the flavor profile while maximizing shelf-life stability. We work with our customers and their processes to enable good practices, better quality and lowered filtration costs.”
Trends in Wine Filtration
Concerning industry trends, Laffey said that ceramic and polymeric have been popular in the crossflow realm. Heyes Filters offers these types, as well as titanium membranes if they are the best solutions for the application.
He has also noticed advances in adjuncts, such as bentonite, a settling agent easy to filter through crossflow. He said that when using adjuncts, not to incapacitate the system by plugging the tube and hollow fibers with a heavy load of particles moving too quickly under pressure. This can result in a costly error in which membranes need to be replaced.
Russell has seen an uptick in the use of Della Toffola, a crossflow supported by Aftek. “It allows for reduction of manpower and the ability to remotely monitor and control the unit,” he said.
Choosing a Filtration Method for Your Winery
When in the market for a new crossflow system, winemakers should work alongside a company with extensive system experience, service backup and available parts and is responsive to customer needs.
“Choose a company that not only can provide you products but can help with the setup and usage,” said Russell of Aftek. “Saving $50 on a membrane only to get a shortened life or use five times the number of cartridges when one might be used all season isn’t a better value. Make sure they understand the process and have good service and assistance.”
Researching filtering techniques helps the winemaker know what to expect before they’ve even made the call to the manufacturer and may make the process–both buying the system and filtering wine–go easier.
“I have often told prospective Heyes Filters’ clients to do their due diligence and research the different crossflow technologies that would best suit their needs, knowing that the systems do not really care what you send them,” Laffey said. “The crossflow system will do its best to process the wine being filtered through it. Quite often, the expectation of the winemaker can be challenging to overcome or satisfy depending on their knowledge of the technology and the ‘prep work’ done on the front end on any given wine style.”