Well, yes, coffee can be bitter. Much like the tannins in wine and tea, the many acidic compounds in coffee can become overwhelming and undesirable in the cup for several reasons. Bitter is such an ambiguous term, though, when judged by an individual’s subjective taste perception. Bitter to one person may be brightness to another. How can bitterness in coffee be truly identified and controlled?
The International Coffee Organization (ICO) defines “bitterness” in coffee as “…a primary taste characterized by the solution of caffeine, quinine and certain alkaloids. This taste is considered desirable up to a certain level and is affected by the degree of roast and brewing process.”
DEGREE OF ROAST: We identify three distinct roast categories for coffee here at Alpen Sierra:
1. Medium: the lightest degree of development of the coffee bean where heat has penetrated the outer layer of the bean and developed it adequately to represent the truest character and terroir of the origin and cultivar of that particular coffee. The resulting flavor will be “dimensional”, meaning it can be tasted all over the palate.
2. Full-City: Truly the peak of flavor development of the coffee, which has all the benefits of medium roast, yet is enhanced by a slight degree of caramelization of sugars on the surface of the bean, adding richness to the cup.
3. Dark: Ranging from medium dark to full dark, this degree reflects full heat penetration of the core of the coffee bean, releasing starches and sugars, triggering volatile chemical reactions and resulting in diminished dimensionality and true representation of the coffee’s terroir, yet increased intensity in the cup.
The most probable degree of roast that would display true and undesirable bitterness is the dark roast. If a roaster’s internal temperature becomes too high during the roast, which happens later in the roast, and not tapered or limited, the coffee beans will become exothermic, meaning that the beans will have absorbed all the heat they can during roasting and then begin to add heat back into the environment. It is this exothermic reaction that will create a gaseous and nasty sharp finish in the coffee.
BREWING PROCESS: Properly roasted coffee is always going to be grind degree sensitive, i.e. the beans must be ground to the correct degree for the brewing application. If coffees are ground too fine for their respective brewing method, they will over-extract acidic compounds in the coffee and result in bitterness in the cup. Oftentimes I hear people say they like to grind their coffee on the fine side to get “more flavor” out of it. This will be true of under-roasted, or baked, coffees, which can be found quite prevalently in the marketplace, read “slow roasted coffee”. Coffees that have been developed to their full flavor potential will always be grind degree sensitive. If you are unsure as to the proper degree of grind, have your local coffee professional prepare a sample on a commercial coffee grinder and use that sample as a benchmark when grinding at home. Buy a burr grinder for accurate and consistently ground coffee and optimum quality brew!
Rule of thumb: the longer the contact time of coffee grounds to water during the brewing process, the coarser the coffee should be ground.
1. Espresso, being a rapid method of extraction (coffee brewing), with a contact time of thirty seconds, should be ground fine. Caution with the stove-top espresso makers – they require a medium degree of grind as the water boils up through the grounds and over-extracts flavor if too finely ground. Fine-ground coffee will also clog the stove top filter baskets.
2. Drip coffee, whether in a V-cone or flat bottom brew basket, should be a medium degree of grind as the contact / extraction time of water to coffee grounds is anywhere from three to five minutes.
3. French press, or press pot, brewing should be coarse medium, as the contact time, although recommended to be four minutes, ends up being longer, because the grounds are retained within the brew – pour the brew off immediately, if possible, to retain balanced flavor.
4. Lastly, coffee prepared in a percolator should be ground coarse for the contact time is quite long. We discourage percolator brewing because it boils coffee and re-brews the coffee through the coffee several times, which will result in bitter coffee,.
The optimum brewing temperatures for coffee range from 196 to 202 degrees Fahrenheit. Water boils at 212 degrees at sea level and that boiling temperature reduces one degree every five hundred feet of elevation gained above sea level. Brewing with boiling water can result in bitterness in the cup.
Should you still be experiencing bitterness in your cup and have addressed the two primary factors, check your brew pots, filter baskets and mugs for dark, oily residue build-up. All contact surfaces of coffee and water during brewing, including your favorite coffee mug, should be squeaky-clean and free of tar and oils. It is this build-up of residues, which oxidizes and rancidifies, that will spoil any and all water and coffee with a bitter taint. There are many products to assist with cleaning brewing equipment, carafes and mugs. Warm, soapy dish water and some good ol’ elbow grease is the easiest, cheapest and fastest. Otherwise, check out products like Puro-Caff and Tabz for overnight dissolving of oily build-up
In closing, many coffees from around the world are naturally high in “favorable” acidity and display a distinct metallic sensation on the palate. This taste characteristic is identified as “brightness” in the cup and is important to aficionados as a quality attribute, yet can also be confused with bitterness by those coffee drinkers with milder taste preferences. This positive characteristic is prevalent in many coffees from Africa and Central America, most notably, Ethiopia, Kenya, Costa Rica and Mexico, to name a few. If you find this brightness undesirable, select milder coffees from regions such as South America and Indonesia. To insure you are getting the best possible quality in the cup, seek coffees that are of the specialty arabica species, are expertly roasted, preferably in small batches, and that are fresh ground and freshly brewed. Enjoy!