Explain the concept of "over-extraction" in coffee brewing.

Over-extraction in coffee brewing refers to the process where too many of the coffee solubles are extracted from the coffee grounds. This typically happens when coffee is brewed for too long or when the grind size is too fine. When coffee is extracted for an extended period or if the grind is overly fine, more bitter compounds are dissolved in the brewing water, leading to undesirable flavors.

The result of over-extraction is often a bitter, harsh taste that overshadows the desirable flavors and aromas of the coffee. This is in contrast to under-extraction, which leads to a lack of flavor complexity and can result in a sour or overly acidic cup. Therefore, understanding the factors that contribute to over-extraction, such as brew time and grind size, is crucial for achieving a balanced and enjoyable coffee flavor.