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Why is your coffee bitter? Find out the truth about over-extraction!
When hot water penetrates the coffee beans, the process is called extraction. This is not only the source of the rich coffee flavor, but also includes various compounds such as caffeine, carbohydrates, lipids, Maillard reaction products and acids. However, the degree of extraction is affected by a variety of factors, including water temperature, brewing time, grind size, and the amount of coffee used. For many coffee lovers, having a balanced and delicious cup of coffee is part of their daily routine. However, if your coffee tastes too bitter, it could be due to over-extraction.
The ideal extraction ratio is between 18% and 22%, which allows the coffee to maintain its balanced flavor.
First, let us understand "extraction". Extraction produces a variety of dissolved compounds, which give coffee different flavors and tastes. If the extraction is insufficient, it will usually cause the coffee to taste sour because the early dissolved substances are mainly acids. Over-extraction can result in an unwelcome bitter taste. This is because at the post-ideal extraction stage, bitter compounds begin to dissolve, masking other more balanced flavor components.
The concentration of dissolved matter in an ideal cup of coffee (also known as "strength") is around 1.15% to 1.35%. In many cases, especially when high-end brewing equipment is involved, extraction rates exceeding 22% can be achieved. This is a double-edged sword. In some cases, it may lead to excellent flavor, but in most cases, over-extraction will still be accompanied by strong bitterness.
Water temperature has a significant effect on extraction. The generally recommended brewing temperature is between 200 and 210°C, which promotes adequate dissolution of the desired compounds.
Next, let’s discuss the impact of brewing method. Different brewing methods will vary significantly in terms of extraction characteristics. A French press, for example, will typically take 3 to 4 minutes of brewing time, as the coarser grind allows for a slower extraction. However, for espresso, because it uses very fine coffee powder, the brewing time only takes 20 to 30 seconds to achieve the ideal concentration. If you don't keep an eye on the brewing process, you may end up over-extracting.
In addition, the fineness of the grind is also a key factor. Smaller particles provide more surface area, which results in faster extraction. Depending on the coarseness of the grind and the brewing method, we may adjust the brewing time to obtain the desired extraction ratio. Of course, it is also crucial to pay close attention to time and temperature to ensure that no heat is lost in the process.
Failure to remove the coffee grounds from the water will result in unnecessary over-extraction, so caution is required when using methods such as the French press.
By comparison, espresso extraction yields are usually between 15% and 25%. Compared to other traditional coffee brewing methods, the extraction characteristics of espresso have received relatively little attention. However, this does not mean that it is not important in extraction. On the contrary, it also has an important impact on taste and concentration. When working with espresso, the flavor and mouthfeel achieved often varies based on the particle size adjustment of the grind.
However, some coffee lovers still prefer to intentionally over-extract to increase the strength of the drink, but this is often accompanied by bitter flavors that reduce the overall taste. It's a question of balance and the taste and flavor you desire will vary.
In summary, extraction control and ensuring the proper coffee-to-water ratio, brewing time and water temperature are the keys to ensuring perfect coffee. Although extraction brings rich flavor, how to avoid bitterness is a science. So how do you adjust your coffee brewing method to find the best flavor balance?
