Does Your Coffee Filter Affect Flavor?

Ever since I started making daily pour overs, I've been using unbleached Melitta #2 coffee filters. I chose unbleached filters because I believed that the bleaching process was inherently "unnatural", and probably used chemical processes that are bad for the environment. For years, then, I have known that the filters added a certain "woody" flavor to my coffee, but I just accepted that as the price to pay for better sustainability.

My dear wife passed on an article to me the other day that changed my mind about this downside of unbleached filters! I also did some more research about environmental issues relating to coffee filter bleaching.

The Flavor Problem Explained... and Solved

Filter paper is composed primarily of cellulose (neutral tasting) and varying amounts of lignin, hemicellulose, extractives/resins and trace processing residues. The off taste I have noticed comes primarily from residual lignin compounds that remain in the paper after pulping and minimal processing. Lignin contains aromatic compounds that can produce woody, earthy, cardboard-like, musty and paper aromas. Hot water extracts these flavors into the brew. Exactly!

Bleaching's purpose is to remove residual lignin, oxidize colored organic compounds, brighten the pulp and reduce flavor-active residues. That is, whitening and and producing a more flavor-neutral filter. So my unbleached filters were missing that crucial processing step. 

The secret to removing the unwanted flavors at home is a simple hot-water rinse! A pre-brew rinse actually does three things:

• Removes the off flavors. A water rinse flushes out loose fibers, soluble lignin fragments, paper dust and volatile compounds. Hot water accelerates this extraction dramatically.
• Preheats the brewer. Prevents initial under-extraction due to cooling of your brew water, specially with a ceramic brewer.
• Seats the filter. A wet filter sticks to the sides of the brewer, sealing gaps that otherwise cause channeling and uneven extraction.

I notice that when rinsing with about 4 ounces of hot water I smell that strong papery aroma. Letting it drain a bit, and following with another 4 ounces of hot water thoroughly rinses the filter. Drain and dump out the water, and begin your brew immediately. The difference in final taste is noticeable!*

Bleaching - Good or Bad?

Before the late 1980's, most pulp was bleached with elemental chlorine gas. The problem? The EPA found this process created toxic chlorinated byproducts, especially dioxins and furans that were discharged in mill wastewater and accumulated in the environment. During the 1990's, the industry rapidly moved toward using chlorine dioxide instead of elemental chlorine because studies show that the Elemental Chlorine Free (ECF) process virtually eliminated the formations of the dioxins that were previously produced. Melitta began to use this oxygen-based bleaching process in 1992, producing white filters without chlorine gas.

Some specialized manufacturers went further, opting for oxygen-, peroxide-, or ozone-based processes instead. Because these processes are more difficult and expensive, they are relatively uncommon in coffee filter products. Chemex is probably the only manufacturer that explicitly uses this chemical-free process; most others claiming "oxygen-bleached" are typically using an ECF process. As is often the case, process information is not easy to obtain. But in general, we can all feel comfortable with using either brown or white filters from an environmental impact perspective.**

I have used both TCF And ECF white filters, and have noticed differences in the brewing results. Some paper textures are thicker, which seem to trap finer particles, resulting in a slower brew and clearer cup of coffee. They seem to be removing the larger bitter-tasting molecules as well, so that may help with your very dark roasts. As always, you may need to change your pour rate, temperature or grind level for optimal pours.

Where I End Up

I started off asking about how filters affect flavor. I've solved this problem for myself by rinsing the brown filter once or twice with hot water, allowing it to drain into my ceramic mug to preheat it as well. That's the main takeaway for this article.

I generally recommend brown Melitta #2 filters. They're low cost and generally available at local grocery stores or directly from Melitta. But I am also comfortable using white Melitta #2's.

Our septic system passes pre-brewing rinse water back into the ground. Used grounds and filters - either white or brown - go into the no-turn continuous compost pile. The filters decay over many months, and with the grounds, are considered a "brown" element in the pile.

Some might say these steps are insignificant - like using a non-disposable straw in a plastic cup. I do understand that the cup of coffee you brew is part of an complicated international food chain of coffee beans, and there are myriad environmental impact points all along the line from tree to cup.

That will always be the case, unless the coffee hand-picked off my own tree, dried in my back yard, manually processed, roasted over a stick fire, ground in a mortal and pestle and brewed using my stream water.

Purchasing coffee that's grown in an environmentally sustainable way one way to have a larger impact than brewing and filtering methods. All Good Earth Roasters coffees are sourced from farmers that care about their soil and growing environment.

We acknowledge that there are tradeoffs in just about everything, and want to be open in discussing complicated subjects like these. We welcome your participation!

-steve

* An unbleached (brown) filter may save a small amount of processing at the paper mill. But if coffee brewers rinse the filter with 5-10 ounces of hot water, aren't we using more resources? The environmental tradeoff isn't always as obvious as it first appears.

** With respect to raw or bleaching processes. Also, any pulp-based disposable filter is an environmental issue itself. There are water-usage tradeoffs with metal mesh filters or cloth filters too. How far you go is a personal choice.