Brewing an excellent cup of coffee is both a science and an art. While we often attribute a coffee’s taste to bean origin, roast, or preparation, there are a number of factors between roasting and sipping that can spoil what should be a delicious, high-quality cup. In this blog, we walk you through our coffee troubleshooting steps, helping you identify the spoiling source and providing suggestions on how to change ‘ick’ to ‘ahh’.
If your coffee tastes bitter or earthy, look at your beans / grounds. During the roasting process, carbon dioxide (CO2) develops inside the coffee bean. When the beans are exposed to air, they lose CO2 and absorb oxygen. (To learn more about this process, click here.) The CO2 must be released before the beans are brewed or you will end up with an off-tasting, unequally extracted, earthy / sour cup of coffee. Beans that have lost too much CO2 are considered stale. Stale beans often taste bitter, have little aroma, and frequently crack. Once you open your bag of coffee, exposing it to oxygen, the degassing process resumes and you generally have 1-2 weeks before the beans / grounds stale. To prolong the freshness of your beans / grounds proper storage is essential.
Coffee is a food product with many extraordinary properties, prime among them is its ability to reflect the flavor and scents of its surroundings. In addition to being air, light, heat, and moister sensitive, coffee is highly absorbent. Coffee stored in unsealed bags will absorb the flavor notes and scents surrounding it. Coffee should also be kept away from direct sunlight, which causes it to stale quickly; from heat, which causes it to lose flavor: from moisture, which it will absorb; and from air, which causes it to lose CO2. To prolong your coffee’s shelf-life, we recommend storing it an air-tight, light-blocked, dry (avoid the freezer and refrigerator!) place. Air-tight and light-blocked, that is your new coffee mantra!
Matching your grind to your brew method is essential to producing a delicious cup of coffee. Grind impacts extraction, which gives coffee its taste. While there are many ways to think of extraction, on a basic level, it reflects the duration and percentage of a ground’s surface area in direct contact with water. Generally, under-extraction occurs when the grounds are too coarse for the brew method (e.g., using coarse grounds in a stovetop espresso brewer) and over-extraction occurs when grounds are too fine for the brew method (e.g., using fine grinds in a french press). Under-extracted coffee tastes weak, sour, and / or watery while over-extracted coffee tastes bitter. If you feel your coffee is either over or under-extracted, try changing your grind setting.
If you are certain your grind is correct and your coffee still tastes off, look at the actual grounds. If they are uneven in size, that could be your problem. For an even cup of coffee, you need even extraction and even extraction requires grounds of a similar size. If your grounds are uneven, it may be time for a new grinder.
Grounds to water ratio
Grind to water ratio is just as important to optimal extraction grind size. If you are confident in your grind and your coffee still tastes weak / sour, you may not be using enough coffee to brew. When too little coffee is used to brew, the grounds essentially drown in water, forcing out both their sweet and sour notes (think of this as a double run — two pots of coffee being made from the same set of grounds). Conversely, brewing with too much coffee means the grounds cannot fully and equally saturate. While grounds to water ratio ultimately comes down to personal taste, we recommend two heaping tablespoons of grounds per six ounces of water.
Coffee is 99% water. The water you use to brew is your coffee’s uncelebrated co-star. You may think of water as a stagehand in coffee’s play but trust us, she’s a co-star. If water quality or temperature is off, your coffee can’t shine. First, water quality. If you drink filtered water, brew with filtered water as any residual or mineral tastes visible in your drinking water will appear in your coffee. Secondly, watch the temperature. Optimal brewing temperature is between 195 and 205 degrees Fahrenheit. Water above 205 degrees burns coffee, destroying volatile oils and gentle flavor notes. Water below 195 degrees fails to extract properly. Burned coffee tastes bitter; under-extracted coffee tastes sour. If you don’t have a thermometer on your brewer or kettle and use a brew method that requires you to pour water directly onto the grounds, after removing the boiling water from its heat source, wait 5-10 seconds before pouring the water over your grounds. If you are using a stovetop brewer or percolator, keep your burner on the lowest possible setting — that smooth, flavorful cup is worth the wait!
Another secret coffee spoiler? Dirty or failing equipment. Brewers, unlike other kitchen appliances, rarely let you see them struggle. There are no beeps or auto-shutoffs that tell you the water heater is failing or the filter is clogged so, you need to rely on your taste buds. If nothing has changed with your coffee or water and your coffee starts to taste off, check your brewer to ensure it is working properly. The first step is generally to clean your machine. Drip brewers, french presses, espresso machines — they all need to be cleaned to remove coffee residue. If you are confident your machine is clean, try a test run using just water. If the water temperature feels too hot or cold, your heater needs to be recalibrated. If the water comes out dirty, you likely need to clean the filter. If that still doesn’t work, it’s time for a new machine.
Timing and storage
Assuming your grounds, coffee, and equipment are perfect, the next big pitfall is timing and brewed coffee storage. If you brew with a pour-over or french press, it is very easy to either under or over-extract your coffee. When brewing with a pour-over, adding too much water to your grounds too quickly can lead to over-extraction. When brewing with a french press, it is easy to accidentally over-extract your grounds by failing to pour the brewed coffee. Even after you’ve depressed the tamper, the grounds are still there and steeping. If you use a drip brewer or stovetop brewer, leaving brewed coffee on a warm burner can cause it to burn. Our advice is to drink your coffee directly after brewing or transfer your freshly brewed coffee to a thermal pot.
Milk, sugar, and spices
Finally, your add-ons! Coffee has thousands of flavor notes that react with the other flavor notes in your mouth and in your cup. If you add dairy to your coffee, recognize the taste and textural qualities it produces. Generally, full-fat dairy adds a creamy, almost nutty flavor. Low-fat and fat-free dairy often subdues a cup and may make it a little watery. Soy milk, creamers, and flavored milks add their flavors to your cup, as will sugar and spice. While you may love these additional flavored add-ons alone, they may not react well with the flavor notes in your coffee. Adding cinnamon or coconut milk, for example, to a peppery Sumatran may make your coffee taste sour. Similarly, adding soy milk to a chocolatey Peruvian coffee will give it an earthy tone, not natural to the bean. To get the most out of your add-ons, use them to either enhance the flavor notes inherent to your coffee (e.g., adding a teaspoon of coco powder to a chocolatey coffee) or to create an exciting contrast (e.g., adding almond milk to a bright, citric Central).
We hope this helps you identify and correct the source of all your coffee ills. To learn more about brew techniques and add-ons, visit our knowledge center.
*We are assuming you are using high-quality arabica beans. If you are not, we strongly suggest you make the switch!