What does 'over-extraction' in coffee brewing indicate?

Over-extraction in coffee brewing means that the coffee grounds have been in contact with water for too long, which leads to the extraction of undesirable compounds. When brewing coffee, the aim is to extract flavors and oils that contribute positively to the taste while avoiding the extraction of bitter and harsh flavors that can develop when the brewing time is extended beyond optimum levels.

When the brewing time is too long, the result can be a cup of coffee that tastes bitter or astringent, as the longer water interacts with the coffee, the more it pulls out these unpleasant compounds. Hence, identifying over-extraction as too long brewing time is crucial for achieving a balanced and enjoyable cup of coffee.

Other factors such as grind size, water temperature, and brewing time play significant roles in the extraction process, but in this case, the definition and effects of over-extraction specifically relate to the duration of brewing. Each element interacts with the others, but over-extraction is most directly associated with exceeding the optimal brewing time.