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What is Coffee Over-Extraction? How to Judge Under-Extraction vs Over-Extraction and Their Effects on Coffee Flavor

Published: 2026-01-27 Author: FrontStreet Coffee

Last Updated: 2026/01/27, Extraction: The process of extracting compounds from raw materials, such as drawing flavor compounds from coffee beans using hot water. Over-extraction occurs when coffee grounds remain in contact with hot water for too long, extracting undesirable compounds along with desirable ones, resulting in bitter, harsh flavors.

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Extraction

Extraction means to squeeze something out or to obtain an extract. In chemistry, extraction refers to extracting valuable substances (flavors) from raw materials (coffee beans). In coffee extraction, the most common method is using hot water to extract flavors from coffee grounds.

Over-extraction

Over-extraction refers to when coffee grounds remain in contact with hot water for too long, or when the ratio of coffee grounds to water is too low. When using drip coffee makers and espresso machines, over-extraction can be caused by grinding the coffee too finely. For manual brewing, it might be due to extraction time being too long. Water temperature that's too high can also lead to over-extraction. Over-extraction extracts too many unwanted substances, such as caffeine, making the coffee taste bitter and unbalanced.

Coffee extraction process showing different stages

Under-extraction

Under-extraction refers to when coffee grounds are in contact with hot water for too short a time, insufficient to extract all flavors from the grounds, resulting in coffee that tastes thin, bitter, and unbalanced. Under-extraction can be caused by grinding coffee too coarsely or water temperature being too low. If the ratio of coffee grounds to water is too high, you'll get under-extracted strong coffee that not only lacks the distinctive characteristics of coffee but also carries a bitter taste.

Extraction Time

Extraction time refers to the duration that coffee grounds are in contact with water, which is a crucial factor for good coffee. Other terms such as brewing time or steeping time also refer to extraction time.