Filtration is an important step in a wine’s path from vine to bottle. It is important because stability and clarity are necessary for a product that is safe to bottle, and is attractive to consumers. With the exception of the final sulfite addition, filtration is the final task before the wine will meet the bottling line. In this article we will explore the “how” and “why” of wine filtration along with the equipment needed to do it.
How Filtration Works
Essentially, filtration works by passing wine through a filter medium, be it a cellulose pad, a pleated cartridge, or some other material of known porosity. As the wine moves through the filter, any microbes, yeast, or other particles larger than the micron rating of the filter are captured and prevented from moving through the filter media. Filtering can produce a crystal clear product and, depending on the micron rating, a wine free of yeast and microbes — in other words: A stable wine.
Why We Filter
With anything in winemaking, there are different camps that feel strongly one way or another about various topics of the craft, and filtration is no different. Fortunately, I am not here to debate the pros and cons of filtration, but rather inform you of why we filter, and the equipment available to us as home winemakers to carry out the task. As for the ages old debate, I will defer that to the Wine Wizard in the article: “Is Filtration Good or Bad for Your Wine,” which you can read at https://winemakermag.com/398-is-filtering-good-or-bad-for-your-wine.
Let us start off with the biggest reason home winemakers filter — clarity. Commercial wineries are expected to produce a consistently clear wine, whereas home winemakers are not under such scrutiny. However, even a single pass through a coarse filter — approximately 5–7 microns — will remove the larger suspended particles and give you an edge in competitions and enable you to produce a professional-looking product in the comfort of your own home. While fining agents and subsequent rackings will suffice in most instances, there will always be that next level of clarity to achieve, by which filtration is the only route.
Considering a consumer’s first impression is a wine’s appearance, clarity is a significant factor — particularly with white and rosé wines. The decision to filter reds is based on artistic/personal preference, or due to necessity (more on this later). Over time, reds will throw sediment anyway, and premium reds are not usually filtered as some oxidation may take place during the process. In some cases, the sediment is a sign of quality. Personally, I filter my reds through a coarse filter just to remove the large particles that may be floating around and visible to the naked eye. I have found this gives me a great looking product and alleviates any fears of floaties in the glass. Later in the article I will discuss which filter size to use when clarification is our main objective.
The other primary reason wine is filtered is for microbial stability. Wines with residual sugar, unfinished malolactic fermentation (MLF), or that have suffered the affects of Brettanomyces or other yeasts and bacteria are at risk for spoilage issues once the wine is in the bottle. These problems can produce a fizzy, off-tasting wine that could even force the bottle to pop its cork, or worse, explode. Filtration for microbial stability is seldom performed in the home setting, usually due to experience, cost, or equipment availability. However, coming close to sterile filtration without the big plate and frame or cross-flow filters you see in wineries is possible.
Without the use of filtration, residual sugar can be addressed with the use of potassium sorbate, and unfinished malolactic fermentation is kept under control with the use of Lysozyme. However, potassium sorbate cannot be used in a wine that has undergone malolactic fermentation as it will result in a geraniol flavor, which is a flaw. Therefore, if you have a wine that has undergone MLF and has residual sugar, getting as close to sterile filtration as possible seems to be your only choice for a stable wine that is safe to bottle.
What Microbes should be Filtered?
The microbes wineries are most interested in filtering out via sterile filtration consist of a number of different yeasts and bacterias. They are:
Yeasts: Brettanomyces species, Kloeckera apiculata, Saccharomyces species, Zygosaccharomyces bailii.
Bacteria: Acetobacter species, Lactobacillus species, Oenococcus oeni, Pediococcus species.
Without a microscope and the know-how, it is impossible to get down to the microbiological level of our wine in the home winemaking setting. This makes it difficult to get specific about what we are trying to filter out. Some of these microbes or yeasts can present themselves with off-flavors or an offensive nose, alerting you to their presence in the wine — making them detectable without the use of specialized equipment or a degree in microbiology. For home winemakers, the things we are looking to filter out most are Saccharomyces species (cultured wine yeast) and Oenococcus oeni (malolactic bacteria). This is just in case alcoholic or malolactic fermentation does not finish and we would rather filter than use additives to stabilize our wine (which is not always an option). Yeasts are in the 5–10 micron (µm) range. Bacteria get smaller in size, for example: Cocci can be from 0.5–3 µm in diameter, bacilli can range from 0.2–2 µm.
Filter Pore Sizes
As you can see, the filter choice does make a difference depending on what you intend to filter. Although these sizes are simplified, it should prove to be a guide to help you choose the right filter for the job and be used as a springboard for further research.
Pore sizes are measured in microns. This means the smaller the number, the tighter the pores in the filter are. Buon Vino pads are rated — the higher the number, the tighter they are. The ability of the filter to remove microbes lends itself to the pore sizes, which are made to be smaller than the yeast and microbes themselves so they cannot pass through the filter media. The usual micron ratings for winemakers are 7, 5, 3, 2, 1, 0.5 and 0.45, along with other sizes for various stages in the process.
To further break down the filter types, there are the “nominal” and “absolute” ratings. The nominal rating will filter out most of the microbes above the micron measurement, whereas the absolute filter rating will filter out everything above the micron rating. The industry standard for sterile filtration is 0.45 µm nominal (although sterilization by microbiological standards is usually 0.2 µm absolute, 0.45 µm is still the standard for sterile filtration in winemaking).
Filtration Choices: Plate and Frame
Home winemakers have numerous good-quality filtration choices that should meet the needs of any individual based on the volume they produce and their specific needs. To start off, let’s take a look at the plate and frame filters.
Buon Vino Mini Jet
This compact unit is made for small-scale filtration: 5–10 gallons (19–38 L) at a time. This is perfect for those working with kits, juice pails, and smaller batches of wine. The Mini jet uses a built-in self-priming Flojet pump to send the wine through the set of three cellulose filter pads. This pump can also be used to rack wine by bypassing the filter pads.
Buon Vino Super Jet
The Super Jet is made for medium-scale filtration: 13–26 gallons (49–98 L) at a time. This unit uses 20 x 20 cm cellulose filter pads to do the job, which have the same ratings as its Mini Jet counterpart. The Super Jet also has a Flojet pump, and like the Mini, can be used for racking wine. This gives you more bang for your buck and allows you to pump large volumes of wine between tanks and other large vessels. The Super Jet is equipped with a pressure gauge so you know when the pads have become clogged with debris and need to be changed.
If you are making higher volumes of wine and have deeper pockets, the Super Jet also has a six-pad option for filtration of up to 60 gallons (227 L) at a time. The three additional pads allow for a longer filtration session without the hassle of replacing pads.
The filter pads for the Mini and Super Jet come in three different grades.
• Coarse Number 1 is approximately 7 microns and is meant for filtration of wines that are clear, but have some large suspended particulates. Perfect for reds and preparing a wine for filtration with tighter pads.
• Polish Number 2 is approximately 2 microns and is meant for filtration of white, rosé, or if you want to further polish a red wine. This set of pads should be used prior to using the number 3 pads.
• Sterile Number 3 is approximately 0.5 microns. Although this pad set is labeled “sterile,” it does not meet the industry standard for sterile filtration of 0.45 nominal. This pad set may remove some yeast, but should not be used in place of potassium sorbate when there is residual sugar present, or in place of Lysozyme if malolactic fermentation failed to finish. When using this pad, be sure to first filter with at least the number two pad set first, as any particulate in the wine will quickly clog up a pad of this micron rating. This pad set would be used if the polish pads did not filter to your liking and you desire a higher degree of brilliant clarity.
For very small volumes, there is another style of filter that I will mention briefly as you may come across it. This is a plate and frame filter that relies on gravity to move the wine or with wine pushed through the filter between kegs with inert gas. However, according to Daniel Pambianchi’s Techniques in Home Winemaking, the gravity versions may introduce excess oxygen into the wine due to the length of time it takes to perform the filtration process. Feel free to research these filters on your own.
Filtration Choices: Inline Filters
The use of inline filters is becoming more popular as vacuum pumps like the Enolmatic, the All in One Wine Pump, and homemade vacuum pump set-ups are being used by home winemakers for various duties around the home winery. A major benefit to using inline filters is oxygen ingress is greatly reduced thanks to the whole filter operation being enclosed. An added bonus is the filter housing is easier to clean and sanitize too. Here are the most popular inline filtration kits for home winemakers:
The Enolmatic has its own filter housing and filter cartridges made specifically for the unit. Filter sizes come in 5, 1, and 0.5 microns, which can be cleaned with Powdered Brewery Wash after filtration to be used again. The filter housing is installed between the vessel of wine and the Enolmatic, and filtration takes place as the wine is bottled. This makes for one less step in handling the wine, which reduces exposure to oxygen and possible contaminants.
All in One Wine Pump
Among the many uses for the All in One Wine Pump, one is filtration. This unit uses an inline 10-inch (25-cm) filter housing, with cartridge filters available in many different micron ratings. A detailed list of equipment and some helpful setup tips to add the filtering feature are provided at www.allinonewinepump.com. It is recommended to filter and bottle in separate sessions, as a steady flow is suggested for effective filtration.
Note: The equipment list should be closely followed as the incorrect filter housing could be purchased if you are not careful. If you choose to buy the items on the list elsewhere, be sure to purchase the filter housing without the red button relief valve, as this valve may open during the vacuum operation preventing a good seal. The housing with the red button can be used with inert gas between kegs and with positive pressure wine pumps.
Filter cartridges, such as a 0.45 nominal sterile cartridges by BevBrite can be purchased from numerous winemaking retailers and are said to work with any 10-inch (25-cm) housing. BevBrite cartridges also come in 5-, 3-, and 1-micron ratings. When reading up on BevBrite or other cartridges, you may see they have an efficiency rating. This simply means what percent of material will be filtered out at that particular micron rating.
As an example, below is each level of efficiency and what they mean for their 3-micron filter:
High Efficiency: Removes 90% of the material 3 micron or larger in a single pass.
Super High Efficiency: Removes 98% of the material 3
micron or larger in a single pass.
Absolute Efficiency: Removes 99.8% of the material 3 micron or larger in a single pass.
Vacuum Pump Build
For those of you that have built or are considering building your own vacuum pump setup for racking and degassing wine, the list of filtration equipment for the All in One Wine Pump can be used. The difference is that the All in One Wine Pump has a precision valve that regulates flow control of the wine. This comes in handy to prevent wine flowing through the filter too fast. To accomplish this on your own system, you can install a thumb valve between the vacuum pump and over-flow container. This allows some air into the line to reduce the flow-rate, while not allowing the air to come in contact with the wine. For more information on building your own vacuum pump racking kit and installing an inline thumb valve, refer to my article “Moving Wine with Pumps” in the April-May 2017 issue of WineMaker.
Tips for a Successful Filtration
1. When using a plate and frame filter, be sure to run a sulfite and citric acid solution through the pads. Doing this not only sanitizes them, but it will also remove paper particles and other debris. One tablespoon of each per gallon (4 L) will do. In my home winery, I run 5 gallons (19 L) of this solution through each set of pads. When I start the filtration procedure, I divert the first bit of liquid coming out of the filter into a pitcher, as it will be mostly water at first.
2. Filtration has its limitations and it can only do so much for the longevity of a wine’s clarity if certain tasks are not carried out during the winemaking process; most notably cold stabilization and protein stability. If a wine is not cold stabilized by exposing it to below-freezing temperatures for a period of time (usually 2–6 weeks depending on the temperature), the wine may throw tartrate crystals, which will settle to the bottom of the bottle when chilled. While these crystals are not harmful, they can be mistaken for glass and they certainly are crunchy! White wines may need to be protein stabilized by using Bentonite. This will prevent a haze from forming and swirling around the bottle when you pull it off the wine rack. No amount of filtration will prevent these two things from happening and they must be completed during the winemaking process.
3. Be sure to filter at the correct stage in the process: Wineries are equipped to filter wine at various stages, no matter the clarity or murkiness of the wine. Home winemakers should stick to filtration at the end of the process when the wine is clear. You may be asking yourself: Why would I filter a wine that is already clear? Filtration should take place after the wine has had ample time for the suspended particles to settle to the bottom of the vessel. This takes time, racking from one vessel to another and possibly the use of a fining agent. Exceptions to this recommendation are wines that fall bright faster than wines made with fruit such as kits and juice pails that lack the fruit matter from grapes. The fruit matter creates sediment that would quickly clog up the filter pads if filtered too soon. To get back to the question you had asked yourself above: If wine is not clear, as in read a newspaper through it clear, the filter pads or cartridge would immediately become clogged, preventing the wine from being filtered.
But if I can read a newspaper through it, then why would I filter my wine in the first place, you may ask. As mentioned earlier, there is another level of clarity to be achieved by filtration. Large particles floating in the carboy may not be visible until the wine goes into the glass, and by then it is too late to filter. The difference is clear in a comparison between filtered and unfiltered wine, especially when you are outside and the sun is shining through your white or rosé. When making the decision about the best time to filter, remember these six words: Filter no wine before its time.
4. Be sure to follow the instructions for whichever filter you use. For example, when using a plate and frame filter like the Mini Jet, be sure to insert the pads with coarse side facing outward toward the black knobs. Also, be sure to use the same grade of pads (don’t mix filter pads of different micron ratings). The wine does not pass successively through the pads; rather it flows in parallel channels through individual pads simultaneously.
5. Prior to filtration, be sure to rack the clean wine off of any sediment as not to clog the filter. Buon Vino sells a pre-filter to install between the wine to be filtered and the filter itself. This protects the pump from oak bits and fruit matter to ensure it lasts.
6. Be sure to sanitize everything that will touch the wine, with the exception of a new filter cartridge, which should be ready to use out of the bag.
7. Ensure your sulfite levels are in line before filtration. Plate and frame filtration can promote oxidation and sulfite is needed to protect the wine. If you have no method of sulfite management, give it a dose prior to filtering your wine.
8. If you intend to filter with a very tight pad such as a 0.5- or 0.45-micron filter media, it is necessary to step-filter down to that particular rating. For example, filtration through a 5-micron pad, then a 2-micron, and then down to 0.8 or 0.5, and then 0.45. It is impossible to go straight to the tighter pads immediately no matter the clarity of the wine. Reds have an even more difficult time moving through the tighter pads in general due to the amount of suspended particles (compared to white and rosé wine). So reds should only ever need a polish filter unless further action is required to achieve microbial stability. At that point, step-filtration is absolutely necessary.
Filtration is a huge subject with a lot of ins and outs, most of which are out of the scope of this article, but with this introductory overview you should be armed with enough information to confidently further research the topic. Rest assured, no matter the volume of wine you make, there is a wine filter for you. And rest easy knowing that there is no wine filter available to us home winemakers that can strip color or flavor. So grab yourself a filter, and get ready to shine!