Final answer:
An over-extracted coffee is typically bitter and astringent due to excessive extraction of undesirable compounds. Extraction balance is critical in brewing to maintain the complex, enjoyable flavor profile of coffee, which is a homogeneous mixture.
Step-by-step explanation:
An over-extracted coffee will typically exhibit flavor characteristics that are bitter, astringent, and may have a harsh or drying sensation on the palate.
This occurs because over-extraction involves pulling too many compounds from the coffee grounds, including undesirable bitter and astringent substances, such as certain phenolic compounds and excessive quantities of caffeine.
Coffee is a complex homogeneous mixture, and its brewing process ultimately aims to achieve a balanced extraction, which allows the sweet and desirable flavor and aroma compounds to dominate, while minimizing the extraction of bitter and astringent components.
It is important to note that there are not more than five cardinal tastes, which include sweet, sour, salt, bitter, and umami. Yet by combining these tastes in various ways, a vast array of flavors are created.
Over-extraction can shift the balance towards the bitter end of the taste spectrum, overwhelming the inherent sweetness and resulting in a less enjoyable cup of coffee.