The brewing time is too long and the water temperature is too high, which are all the reasons for the excessive extraction of coffee.

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Over-extracted coffee.

Over-extracted coffee means that too much soluble matter is brought out of coffee, and this extraction results in bad flavor.

Imagine a cup of premium espresso with an extraction time of 40-50 seconds. Don't pretend you haven't had this over-extracted coffee. This coffee will be bitter, dry and hollow, which are the three most obvious characteristics of over-extracted coffee. Let's look at these characteristics again.

Bitterness: We've all had bitter coffee. Over-extracted coffee is really bitter, and unless I'm drinking Campari bitters, I don't want to drink it that bitter. Much of the bitterness comes from caffeine, but bitterness is also linked to many other chemical processes. Deep-roasted coffee reaches a charred state and forms more bitter chemicals.

Dryness: It is very uncomfortable to drink coffee that feels dry in coffee, because dryness is a strong and lasting feeling. This feeling is called astringency, just like when you drink unsweetened black tea, new wine, or over-brewed white wine. The astringency in the wine comes from the polyphenol effect: chemicals that are easily found in plants, seeds, and bark, which may also be responsible for the dry taste of coffee. Polyphenols are bitter and combine with proteins in your saliva, which is commonly understood as drying your tongue and producing a rustiness or dryness in your mouth (this should not be confused with "crunchy" and "dry" in wine, adjectives that indicate distinct acidity or low sweetness, not necessarily taste).

Hollowness: Coffee feels empty and lifeless, like extracting the light from the coffee and killing the good stuff in the process. Coffee with good extraction will leave you with a rich, delicious, smooth and mouth-watering taste. Over-extracted coffee is hollow, coarse, and obnoxious bland. It's this coffee that lacks flavor and character.

These are the taste characteristics of over-extracted flavors, and there are certainly more adjectives, but these are the easiest to recognize, which also reminds you not to rush over-extracted coffee.

The most important thing about these vacuous flavors is that they are common and can be extracted from the world's noblest Rosedale coffee, as well as from inferior, harsh coffee. These flavors are not pleasing, and most of the people reading this article are looking for specialty coffee, which means we try to create special coffee for consumers so that consumers will pay more to taste it, and the error of insufficient extraction is so abrupt.