Get Crystal Clear About Filtration

This Article Originally Appeared 
in the Dec/Jan 18/19 Issue of 
Winemaker Magazine

Filtration is an important step in the 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. As 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. Which ever camp you find yourself in, I am here to tell you filtration is easily achieved at home, resulting in a brilliant looking product you will be confident to enter into competitions and proud to enjoy with family and friends. In this article we will explore the how and why of wine filtration along with the equipment needed to do it.

How Filtration Works

First off, we must take a minute to explain what filtration is. Essentially filtration works by passing wine through a filter media, be it a cellulose pad or cartridge. 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. Producing a crystal clear product, and depending on the micron rating, free of yeast and microbes, in other words: a stable wine.

Why We Filter

Clarity

Let us start off with the biggest reason home wine makers filter-Clarity. Commercial wineries are expected to produce a consistently clear wine, whereas home wine makers 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 Rose’ wines. The decision to filter Reds is based on artistic / personal preference, or due to necessity (I will clarify on this decision below). 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 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.

Microbial Stability

Another reason wine is filtered is for microbial stability. Wines with residual sugar, unfinished malolactic fermentation (MLF) or have suffered the affects of Brettenomyces or other yeasts and bacteria, are at risk for spoilage issues once the wine is in the bottle (although word on the street is if there is Brettenomyces detected in the winery, it is time to burn it down. This is a joke of course). 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. Coming close to sterile filtration without the big plate and frame or cross-flow filters you see in wineries is possible (I will expand more on this later).

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, 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.

How Do I Know What Microbes I Want to Filter?

Examples of the microbes wineries are most interested in filtering out via sterile filtration 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, which makes them detectable without the use of a specialized equipment or a degree in microbiology. But, in our situation 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. As you can see the filter choice does make a difference in 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. (Let’s Be Clear About Filtration by: Greg Howell (2008)

Filter Pore Sizes

Pore sizes are measured in microns (µm). 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 (More on this below). 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, not allowing them to 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 what is called the Nominal and Absolute rating. 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 it is not sterile by microbiological standards (which is 0.2 µm) .45 µm is still the standard for sterile filtration in wine making.

In an effort to assist you finding a good fit for your home winery, below are filter units available to the home winemaker for all yearly volumes produced.

The Mini Jet

This compact unit is made for small scale filtration: 5-10 gallons (20-40L) at a time. This is perfect for those of you working with kits, juice pails and smaller batches of wine. The Mini jet uses a built in self-priming Flo-Jet 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.

Super Jet

The super jet is made for medium scale filtration: 13-26 gallons (50-100L) at a time. This unit uses 20×20 cm cellulose filters pads to do the job, and come in the same rating as its Mini Jet counterpart. The Super Jet has 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 at a time. The extra 3 pads allow for a longer filtration session without the hassle of replacing pads. It can also be used for racking wine from one vessel to another, which is great as another piece of equipment is not needed for wine transfer.

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 particulate. 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, rose, 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 .5 microns. Although this pad set is labeled "sterile", it does not meet the industry standard of sterile filtration, which is .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 wine higher degree of clarity.

For very small volumes, there is a plate and frame filter on various wine making websites. This filter can be used by gravity or the wine pushed through the filter between kegs with inert gas. However, according to Techniques in Home Winemaking By: Daniel Pambianchi (1999) page 177, 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.

Inline filters and Vacuum Pumps

The use of inline filters is becoming more popular as vacuum pumps like the Enolmatic, the All in In One Wine Pump, and home made 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. Below are inline filtration kits for home winemakers.

The 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" filter housing, with cartridge filters available in many different micron ratings. The owner and creator of the All in One Wine Pump, Steve Helsper provides a detailed list of equipment and some helpful set up tips at allinonewinepump.com. This equipment can be purchased from filtersfast.com. It is recommended to filter and bottle in separate sessions, as a steady flow is warranted 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 else ware, 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 wine pumps.

The filter cartridges, such as a .45 nominal sterile cartridges by BevBrite can be purchased from Morewine, as these cartridges are said to work with any 10" 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.

(Efficiency ratings from Morewine!)

The Enolmatic

The Enolmatic has its own filter housing and filter cartridges made specifically for the unit. Filter sizes come in 5, 1 and .5 microns, which can be cleaned with Powder 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 other baddies.

Vacuum Pump Build

For those of you that have built their own vacuum pump set-ups 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 remedy this, you can install a thumb valve in between the vacuum pump and over-flow container. This allows some air into the line to reduce the flow-rate, of which does not come in contact with the wine. For more information on building your own vacuum pump racking kit and installing an inline thumb valve, please see my article Moving Wine and Using Pumps in the Apr/May 2017 issue of Winemaker Magazine.

Tips for a Successful Filtration

1. When using a plate and frame filter, be sure to run a sulfite 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 will do. In my home winery, I run 5 gallons of this water 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 wine making 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 is exposed to), the wine will throw tartrate crystals which will settle to the bottom of the bottle when chilled. While these crystals are not harmful, they can by mistaken for glass and they certainly are crunchy! White wines should also be protein stabilized by using Bentonite. This will prevent a haze from form 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 need to 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 in the process, no matter the clarity or murkiness of the wine. Whereas we homers 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 to 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 the this recommendation are wines that fall bright faster than wines made with fruit such as kits and juice pails which 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, why would I filter? As mentioned above, 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 later 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 rose; the word brilliant comes to mind. When making the decision about the best time to filter, remember these six words: Filter no wine before it’s time.
4. Be sure to follow the instructions for which ever 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, you cannot mix filter pads of different micron ratings.
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 has a long life.
6. This should go without saying, but 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 .5 or even a .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 1 micron, and then down to .8 or .5 then .45 is recommended. It is impossible to go straight to the tighter pads immediately no matter then 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 Rose’ 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.

In Conclusion

As you can see filtration is a huge subject with a lot of ins and outs, most are out of the scope of this article. I feel in this article we just scratched the surface and this topic will require further research on your part. But rest assured no matter what volume of wine you make, there is a wine filter for you. Forget the rumors and hearsay you have heard about what filtration can do to your wine, ask yourself what it can do for your wine. And rest easy knowing that there is no wine filter available to us homers that can strip color or flavor. So grab yourself a filter, and get ready to shine!

Let’s Be Clear About Filtration by: Greg Howell (2008) Australian and New Zealand Grape Grower and Winemaker Issue 538 page 108-112

Techniques in Home Winemaking by: Daniel Pambianchi (1999)