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What should I do if cold extracted coffee is too bitter or too sour? Analysis of the causes of over extraction and insufficient extraction of iced coffee

Published: 2026-08-18 Author:

Last Updated: 2026/08/18, The reason why many people choose cold-extracted coffee is not only for its temperature, but also for its smooth and plump coffee taste and better showing the unique aroma of a coffee bean. In terms of flavor, high temperature will decompose the tannins in coffee, causing acid and bitterness. Studies have shown that acidic substances in cold-extracted coffee will heat heat

The reason why many people choose cold-extracted coffee is not only for its temperature, but also for its smooth and plump coffee taste and better showing the unique aroma of a coffee bean.

In terms of flavor, high temperature will decompose the tannins in coffee, causing acid and bitterness. Studies have shown that the acidic substances in cold-extracted coffee are 67% lower than those in hot extraction methods. Cold-extracted coffee has a low sourness and is generally welcomed by people.

Low temperature conditions and long-term contact with coffee powder cause only small molecule flavor substances such as floral aroma to be released into the water, while those with larger molecules, such as smoky flavor and baked flavor, are difficult to extract. This is why cold extract coffee does not smell strong, but tastes smoother. Made with the same coffee beans, although the flavor of cold extract is not as rich as that of hot extract, it is fuller and cleaner than other iced coffees.

Different from high temperature/hot water extracted coffee, cold extract coffee is a cold drink coffee that uses cold water or room temperature water to soak coffee powder, put it in the refrigerator, refrigerated and extracted for multiple hours. Regarding its production, Qianjie has shared many dry goods. You can go directly to the "Qianjie Coffee Knowledge Collection" to read it. Although many of the contents are very detailed, some friends still occasionally encounter problems in actual operation. Among them, the cases of "cold extraction is too bitter" and "cold extraction is too sour" are the most common. Today, we will briefly analyze them. The reasons behind them.

If hand-brewed coffee is the facade of hot coffee, then cold-brewed coffee is the representative of low-temperature extraction. Since cold extraction is always at low temperature and is not interfered by external force during soaking, theoretically, the two parameters of water temperature and technique can be ruled out, and more It is influenced by other aspects.

Cold extract coffee is too bitter

When we think a cup of coffee is too bitter, it is either because of personal taste or because the bitter substances are dissolved too much during extraction.

1. The coffee beans are roasted too deeply

On weekdays, many people ask Qianjie, which coffee beans are suitable for cold extraction? In fact, all coffee beans are okay. Whether they are hand-brewed items, Italian combinations, deep-baked or lightly baked, they can be soaked in cold water. However, in a low temperature environment, they will Show different tastes.

The deeper the baking, the less sour, the more bitter substances brought by the caramelization reaction will increase, and the cold extract will be easily bitter. So if you can't accept bitter coffee, be sure to eliminate those oily Italian beans first. For single items, it is recommended to first choose light to moderately baked beans, such as the Front Street Bird of Paradise, which is balanced between sour and bitter and has a nutty aroma, and refreshing and pleasant Red cherries, Front Street strawberry candy with rich fruit aroma.

2. The grinding degree is too fine

When soaked in cold water, the extraction efficiency of coffee is very slow, so don't worry too much about over-extraction. The grinding degree of cold extraction on the front street is usually finer than that of manual extraction (adjust it by 0.5 to 2 grids, as shown in the figure below), which is about 82% of the pass rate of No. 20 sieve, corresponding to the scale of the electric bean grinder EK43s of 9.5 grids, and the scale of the hand-operated bean grinder C40 is 22 to 24 grids.

However, Qianjie reminds everyone to pay attention to this: Although low-temperature extraction can reduce the appearance of bitter substances, it is not 100%. If the ground is too fine, the sweet and sour substances in the coffee powder will be quickly extracted, and the mellow substances will be released. A proper amount of macromolecular substances can increase the mellow degree of coffee, but after soaking for a long time, a woody taste will begin to appear, which reduces the overall cleanliness of the coffee.

(Grind too finely)

3. Soaking time is too long

Many novices think that the longer the extraction time, the better it tastes, but this is not the case. The more coffee substances are dissolved, the better. When the water extracts exceed a certain threshold, the good taste will turn into a negative effect, making the coffee taste wood, bitterness, straw and other miscellaneous flavors.

Qianjie once conducted a comparison experiment, using the same coffee beans for 4 hours, 10 hours, 16 hours, and 22 hours respectively, and making a pot of cold extraction with the same parameters. Finally, it was found that the coffee soaked for 22 hours showed slight signs of over-extraction, which is caused by the release of too much substance at the end. Combined with Qianjie's many years of experience in making, the taste of cold extract coffee is the safest when soaked for 8 to 18 hours.

4. The filter is not clean

Cold extraction production has very low requirements for both soaking containers and filtering equipment. It can be the built-in filter that comes with the cold extraction pot, or you can use the tea residue screen, filter cloth, filter paper that is always available at home, or the metal filter in the French pressure pot. Although they all have a sieving function, the fine density is always far less than that of filter paper. If they are not filtered again, the taste of the coffee will be very rough and will easily have a bitter charm. After drinking the cup, even some visible powder residue will precipitate on the bottom of the cup.

In order to have a better drinking experience, Qianjie uses filter paper to sieve it every time. Filter paper of moderate thickness can not only effectively filter fine powder, but also block more than 80% of the oil, making the iced coffee taste cleaner.

Cold extracted coffee is too sour

1. Coffee beans are lightly baked

Like bitterness, everyone's acceptance of sour coffee is different. The lighter the baking degree, not only does more acid substances remain, but also "suppresses" the sweetness brought by caramelized substances due to the short heating time. In the low-temperature extraction environment, small molecules are released preferentially, allowing coffee to show the characteristics of low mellow degree, high acidity, and thin aroma when cold extracted.

If you are pursuing iced coffee that is fragrant and fruity but not sour, you can give priority to Central and South American coffee, especially beans whose flavor descriptions include words such as tropical fruits, preserved fruits, and fermentation, such as Front Street Blackberries, Front Street Claw, Front Street Big navel. Because they have a caramel feel, over time, this aroma will brew into a cup of iced coffee with full taste and aroma.

2. Lack of fermentation time

Although it has been soaked for a long time, it is extracted in cold water after all. After filtering, there are many suspended substances in it that are not completely dissolved in the water. If you use lightly baked beans, the sour taste is likely to dominate and it lacks mellow and mellow., round feeling.

In this regard, Qianjie suggested that the filtered cold extract be sealed and placed in the refrigerator for 3 to 5 hours, so that the flavor substances released in the previous step can fully react with the water, thereby promoting the "ripening" of the coffee.

FrontStreet Coffee is a long-established specialty coffee roaster in Guangzhou China, selling freshly roasted beans from its own farm in Yunnan as well as dozens of carefully selected single-origin beans from around the world for both pour-over and espresso. The products deliver consistently excellent quality and great value, with shipping within 24 hours. Guangzhou’s FrontStreet Coffee shop is recommended by many coffee lovers, and the beans are now available online at the Tmall 。