Methods for Distilled Spirits Filtration
Last updated: 6/2021
Applies to: Beverage producers looking to evaluate filtration equipment and media for use with distilled spirits. It outlines general considerations for filtering various types of spirits and provides options for suitable equipment/media.
The filtration of extra-precious liquids such as distilled spirits can be both challenging and intimidating. The goal of filtration is to improve the product by removing contaminants which mask the quality components that contribute to flavor, color, mouthfeel etc. In turn, filtration reveals the true beauty of what lies beneath. Fortunately, there are many different options for achieving this irrespective of batch size.
CONSIDERATIONS FOR DISTILLING FILTRATION
Distilling filtration is much different than that of other alcoholic beverages. Due to high alcohol levels, sterile filtration is not necessary like in many other drinks. Although, due to the high cost per volume, filtration loss is of more concern. Further complicating things, the distilled spirits category is also quite broad, and different products require different filtration considerations. For example:
- Barrel-aged spirits: concerns include catching large, suspended solids like barrel char and removing fatty acids
- Neutral, colorless spirits: concerns include ensuring visual brightness and neutral color & aroma
- Fruit-based spirits: concerns include removing colloidal material like pectin
- Spirits with post-distillation additions: even if the product has been filtered, instabilities can show up later due to the ever-changing solubility of additions in a high alcohol matrix
To accomplish the most consistent filtrate quality of any batch size, it is important to identify what you’re trying to remove (particulate haze, colloidal haze, or both) and then identify the most appropriate equipment and filter media for the job. It is always better to start out with a balanced amount of dirt-holding capacity consisting of surface, depth, and adsorption capabilities, rather than to end up with inconsistent filtrate quality halfway through a run. As batch size and colloidal load increases, so too should the surface, depth and adsorption capabilities of your media.
To watch short video examples about each type of filtration, check out our Filtration Series playlist on YouTube.
Bag filters are a surface filtration step to catch bigger particles, such as barrel char or fruit and spice particles to lighten the load before a more substantial depth filtration. Bag filters have very low depth capacity and practically no adsorption capabilities. They are a closed system and can be used with either the mesh basket that comes with most models or add a welded (i.e. not stitched), polypropylene felt bag to help with efficiency.
Bag filters are popular in bigger facilities where high flow rates are required when unloading bulk containers on the way to storage tanks, or even on the way to packaging. Bag filters are usually available in as coarse as 200 micron and as tight as 1-micron porosities.
Cartridge filtration is a very popular method of surface and depth filtration because of the lower price of the media and housings. The closed format of the cartridge housing means a safer, more sanitary, and fume-free environment. You can certainly expect a more consistent filtrate quality in comparison to a bag filter. Polypropylene cartridges are used for depth filtration, and membrane cartridges have absorption capabilities that respect the aromatics of sensitive products.
Some distilleries prefer to use membrane media to better control their filtrate consistency and remove colloidal haze on small batches. Membranes do not have much depth capacity; compared to other depth filters, but they are high precision filters because their pores stay rigid and can handle many pressure spikes throughout the lifespan of the media without being compromised. For this reason, it is common to use them on the packaging line to ensure a consistently particulate-free final product.
SIZING TIPS: For small batch filtration it is best to use a 30” code 7 cartridge housing so that you have the option to use 10”, 20” or 30” cartridges in that housing since the code 7 adaptor has two locking tabs to keep a shorter cartridges in-place in a taller cartridge housing. Cartridge housings are also available in multi-round sizes like 3-round, 5-round, etc. so that that number of cartridges can fit in the same housing; thereby increasing your surface area and flow rates.Shop Filter Cartridges
Filter sheet technology has been around for over 130 years and it has been the traditional method and media for turbidity reduction and haze removal in many beverages, including distilled spirits. Sheet media is constructed of varying combinations of cellulose, resin and filter aids like perlite and diatomaceous earth. You can also find 100% cellulose sheets that contain no filter aids and subsequently no heavy metals. Filter sheets are available in multiple grades to cover a wide range of applications including:
- filtration of liqueurs
- chill haze reduction in brown spirits
- brilliant polishing of white spirits.
For larger batches where extra dirt-holding capacity is necessary to ensure consistent filtrate quality, cellulose-based media (from sheet or lenticular filters) will outperform the cartridge filters of the same or higher surface area. Sheet filter units also have the flexibility to add or remove sheets to fit the batch size, flow rate or the specific product to be filtered. Additionally, a diversion chamber can be added, allowing the filtration through two grades of media in a single pass.
While effective, sheet filters do have their disadvantages:
- Setup, tear-down, and cleaning is labor-intensive.
- Footprint is large for the amount of filtration surface area.
- Drip loss can result in unsanitary conditions and alcohol exposure to the surrounding environment. A ventilation system is sometimes required to minimize the exposure to volatile organic compounds.
- Only stainless steel or polypropylene plates are suitable for long-term exposure to high ethanol levels (not the standard Noryl plastic plates)
Lenticular filter technology is a great choice for spirits filtration. The lenticular media is the same cellulose-based media that we find in filter sheets, but it is assembled in a modular format. This format lends several advantages over sheet filtration:
- Smaller footprint per filtration surface area
- Easy setup, takedown, and maintenance
- Closed system with zero drip loss or escape of volatiles
- Flexible sizing – format allows you to use fewer modules in a housing for smaller batches more modules for larger batches
Some disadvantages include not being able to mix different grades in the same housing; However, they are available in 100% cellulose grades that contain zero filter aid so an extra step to remove heavy metals is not necessary.
The depth filtration technology with the most clout in the distilled spirits world is Pall SUPRApak™ media because of the unique Edge flow technology in the design. This enables even the larger facilities to filter out lipids and long chain fatty acids without the additional cost of chilling first. Unlike typical lenticular modules, SUPRApak modules have an entirely different design and flow configuration to maximize the surface, depth and adsorption mechanisms of filtration that normally occur in sheet media. This means that during a filtration, the media is used a lot more efficiently and because of this longer distance that the liquid must travel, you can use a coarser grade compared to regular sheet media and obtain the same filtrate quality and consistency. Contact us for more information on Pall SUPRAPak housings and media.
Pressure Leaf Filtration
Also known as DE (diatomaceous earth) or Kieselgühr filtration, pressure leaf filtration has traditionally been used for large scale production due to the highest depth, adsorption, and surface filtration capabilities. With pressure leaf filtration, the filtration matrix is built during the filtration process; These filters have stainless steel screens that house canvas. The canvas is typically pre-coated with cellulose and then followed with varying amounts of powdered diatomaceous earth (fossilized algae), and/or perlite (volcanic glass) in progressively finer consistency. That product is then dosed with the product during filtration to build a continuous cake or filter media matrix.
This method of filtration is very dependent on the operator who must be highly skilled and focused to produce a consistent filtrate quality each time. The equipment has feed and recirculation pumps built-in that must be explosion proofed for safe operation. The maintenance on this filter type can be extensive. One advantage is that the media is still relatively inexpensive, and you can add a layer of powdered carbon to remove flavor and color at the same time as a depth filtration pass. Working with powdered filter aid can be messy and depending on the choice of filter aid, can pose various health risks.
What about Carbon?
Activated carbon is used in the filtration of spirits to remove color and flavor, especially in white spirits. Working with bulk carbon can be especially messy and requires additional depth filter steps to remove very fine carbon dust from bulk product.
A variety of food and beverage grade carbon embedded media choices are available in sheet, lenticular and even cartridges. It is important for a product to be brightly polished prior to the carbon step so that the media isn’t prematurely blinded with suspended solids.Shop ScottCart Carbon