What contributes to over-extraction in coffee brewing?

Excessively long brewing times can lead to over-extraction in coffee brewing because, during an extended contact between water and coffee grounds, more soluble compounds are dissolved than desired. While the initial extraction involves the desirable flavors and aromas, prolonged brewing allows for the extraction of unwanted bitter compounds and undesirable flavors.

Over-extraction often results in a brew that tastes harsh, bitter, and unpleasant, as these compounds typically contribute to astringency rather than the delicate flavors that are sought after in a well-brewed cup of coffee. This emphasizes the importance of timing in the brewing process to ensure that only the right flavors are extracted, resulting in a balanced and enjoyable cup.

Other factors like grind size and water temperature also play roles in extraction, but excessive brewing time is particularly impactful when it comes to over-extraction.