Why does pour-over coffee taste burnt, bitter, or astringent?

Bitterness in home pour-over usually traces back to four causes: the beans' own flavor profile, how long they have been stored, the grind size and proportion of fines, and the brewing water temperature. Each can be checked and corrected in turn, which is more reliable than changing everything at once when a cup turns harsh or astringent.

Some beans carry nutty and dark chocolate notes by nature, such as Mandheling or Blue Mountain, and that bittersweet character is not the same as scorched bitterness. Reading the flavor description when buying helps match the bean to your taste, and adjusting grind and water temperature addresses the brewing side.

Many coffee enthusiasts who brew pour-over at home often encounter coffee that is bitter or even has a scorched, astringent taste. This bitterness may come from the roasting profile of the coffee beans themselves, or it may be closely related to how long the beans have been stored, the grind size, the proportion of fines, and the brewing water temperature. Starting from Front Street Coffee's practical experience, this article analyzes four common causes of bitterness one by one and provides specific, actionable adjustment plans, including how to choose beans based on flavor descriptions, how to judge the optimal flavor period, how to calibrate grind size, and how to troubleshoot water temperature issues, helping you more accurately identify the problem and brew a smoother pour-over coffee.

Recently, a friend asked Front Street: what should you do if your home pour-over coffee often turns out bitter? Today, Front Street will explain the reasons why coffee brews bitter and how to avoid them!

Cause One: The coffee beans themselves have an inherently bitter flavor profile

Coffee beans themselves have many kinds of flavors: fruity acidic coffees, honey-and-brown-sugar sweet coffees, and nutty-and-cocoa bitter coffees. If you brew Front Street Mandheling or Front Street Blue Mountain, these coffees inherently carry nutty and dark chocolate flavors, so they will inevitably have this type of bittersweet taste when brewed (note: the bitterness mentioned here is not the same as scorched bitterness or astringency; it is roasting aroma + sweet aftertaste + a rich mouthfeel). For friends who do not like this type of coffee, the bitterness of nuts and dark chocolate is not very different from scorched bitterness or astringency.

Solution: When buying beans, consumers should pay more attention to the flavor description section. Although the flavors described there may seem somewhat impressionistic, you can still tell what flavor type the coffee bean belongs to, and thereby choose the coffee beans that suit your taste.

If you like floral coffee, buy Front Street Panama Boquete Geisha; if you want a rich fruity profile, Front Street Strawberry Candy and Front Street Blackberry are the first choice; if you are after a more vibrant fruit flavor, Front Street Sidra and Front Street Big Belly are recommended. They all come from Colombia's Finca La Divisa, where you can taste rich layers of passion fruit, grape, and blackcurrant juice.

Cause Two: Coffee beans stored too long lose their flavor

The optimal flavor period of roasted coffee beans is relatively short. One reason stores design packaging in capacities between 100 and 227 grams is also to take into account consumers' consumption speed and the optimal flavor period. If you consume 15 grams of coffee beans per day, a 227-gram bag will be finished in exactly half a month, which also matches coffee's optimal flavor window.

Generally, the optimal flavor period for pour-over coffee beans is 4-30 days from the roast date. The longer they are stored, the more flavor compounds in the coffee dissipate. You can reach this conclusion by comparing the smell of fresh coffee beans with beans that have been stored for a long time. Fresh coffee beans smell very aromatic, which is what we often call the "coffee smell," while old coffee beans carry a woody, greasy odor. Coffee beans that have lost flavor compounds will naturally brew with a woody bitterness.

Solution: The best way to solve this problem is to drink it faster and not leave expired beans behind! But Front Street believes the most important thing is to learn to judge the bean's optimal flavor period. Looking at the roast date plus 30 days is one method, but not all coffees have a fixed 30-day optimal flavor period. Thirty days is only a general summary. Some beans have a longer optimal flavor period than 30 days, and some shorter; proper storage will also make it longer than improper storage. So to judge whether the optimal flavor period has passed, you can use whether the bloom expands and releases gas as an indicator. If there is no reaction at all after pouring water, it has most likely passed its optimal flavor period.

Cause Three: Coffee is ground too fine or there are too many fines

Grinding coffee too fine and having too many fines are two different situations, but both are grind-related causes of scorched bitterness during brewing. These two situations show different layered behavior during brewing. Coffee ground too fine specifically manifests as the coffee bed descending very slowly from start to finish, with the overall extraction time exceeding 2 minutes 30 seconds. Too many fines often manifests as the coffee bed descending normally in the early stage, then slowing down more and more later, and may even clog.

Solution: The solution for grinding too fine is very simple: just adjust coarser to normal. Pour-over grind reference: light roast 80% passing a No. 20 sieve, dark roast 70% passing a No. 20 sieve.

Too many fines (uneven grinding) is caused by the quality of the grinder. There are three solutions: first, upgrade to a better-quality grinder; second, use a fines sifter to remove the fines; third, during brewing, cut off the clogged tail-end coffee liquid and then add the corresponding amount of water to return it to the appropriate concentration.

Cause Four: Water temperature too high

Water temperature that is too high can also cause coffee to develop scorched bitterness. Although everyone knows this principle, people are often misled by their own experience. For example, if you often brew a certain bean and using 93°C produces very good flavor, over time it becomes habit, and when brewing coffee beans of a seemingly similar roast level, you will also use 93°C. This can lead to not even realizing that the water temperature is too high.

For example, when brewing Blue Mountain coffee grounds, with all other parameters fixed, using 88°C can express Blue Mountain's balance very well, but using 89°C makes it seem too bitter and unbalanced. Yes, it is often just a difference of 1°C!

Generally, judging whether the water temperature is too high is based on two conditions: first, whether a reasonable temperature range is being used, that is, 90-93°C for medium-light roast and 86-89°C for medium-dark roast; second, if the above conditions are met and causes such as coffee beans, date, and grind size have been ruled out, then judge whether the water temperature is too high.

The above content is compiled by CoffeeHunters, a coffee news website.