Chill filtration for spirits is a relatively new process for filtering spirits. It is effective at eliminating the chill haze that happens when unfiltered spirits get cold, such as when served over ice or when a bottle sits in cold conditions. When a consumer sees a bottle that has chill haze, such as a bottle in a liquor store sitting next to a door on a very cold winter’s night, they might think the spirit is bad or contaminated with something. That is not true and bringing the bottle back up to a standard room temperature will eliminate the haze. The haze is simply vegetable oils that have condensed in the alcohol. The lower the proof of the alcohol, the more likely chill haze will happen. Those oils contain some flavor so chill filtering does remove flavor from the spirit. This is why many consumers want spirits that are not chill-filtered. However, not all spirits should be left un-chill filtered.
Chill filtration has only been around since the 1960s when the technology for cooling the spirits became cheap enough to make it economically feasible. The distillers would chill the spirits down to below the freezing level of water, 32 degrees Fahrenheit or 0 degrees Celsius, and then run this liquid through filters to remove the condensed oils. These filters have different levels of ability to filter depending upon the porousness of the filtering material. The lower the proof of the spirit, the more filtration needs to be done to remove the oils, and the more flavor that is removed. The temperature the distiller chills the liquid down to also has an effect on the process. It is a complicated process.
If chill filtration is removing flavor, then why do distillers do it? To prevent chill haze is the obvious reason, but there are other reasons as well. Chill filtration will also remove other elements from the spirits such as tannins from the barrel aging. Sometimes by removing some of a dominant flavor, other more pleasant flavors are allowed come forward in the taste.
I recently had discussions with Willie Pratt and Andrea Wilson about what they do to filter Michter’s whiskey. Willie Pratt spent a large part of his career working with filtered whiskey. Pratt states that the first thing to remember with filtering whiskey is that it is not a “one size fits all” process. Each whiskey needs to be studied and samples need to be filtered using different methods of filtration or different types of filters and temperatures in the chill filtration. Pratt believes that the goal is to remove as little flavor as possible while reducing some flavors to let others shine through in the whiskey. Andrea Wilson points out that chill filtration is just one of three types of filtration processes they have available to filter Michter’s whiskeys. This is not cheap. The multiple systems cost money and it takes time and labor to do the testing to find what they believe is the best method for each expression of whiskey. Even then, Wilson points out, what works for one bottling of a whiskey may not work as well for the same type at a later date and they do testing before each bottling. Barrels are unpredictable and just because you aged the same mash bill for the same amount of time, there are many factors that can change what was going on in those barrels, so every small batch can be different and adjustments must be made to the filtration.
I once had a bottle of Prohibition era Old Taylor that was 18 years old and tasted like a barrel stave. I placed the pint in the freezer for a while and ran it through a coffee filter. It changed the flavor and took a lot of bitter tannins out of the Bourbon. This experiment convinced me that there is a need for chill filtration. The whiskey was still pretty tannic and bitter, but then again a freezer and a coffee filter is not nearly the chill filtration process done at distilleries.
Chill filtration is simply another step in making a flavor profile. There is nothing wrong with many unfiltered whiskeys, but then there are some that I have had that would have benefited by being chill-filtered. The decision on whether to filter the whiskey or not, and if so, what type of filtration to use, is best left to the producer of the brand. After all, the flavor in the bottle is what the consumer is going to judge their product by when deciding if they are going to purchase a second bottle or not. Never assume that if a whiskey is chill-filtered it is inferior in some way.
Photos Courtesy of Maggie Kimberl