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What is the reason for the turbid coffee? Why does the brewed coffee have fat? Can I drink the coffee if it is not clean?

Published: 2026-04-06 Author:

Last Updated: 2026/04/06, When we talk about the quality of a thing, we always conduct a comprehensive evaluation from multiple perspectives or multiple indicators. Take coffee as an example. The aroma, taste, and length of sweetness of coffee are all evaluation criteria for the quality of a cup of coffee. However, there are also some friends who will be independent and use the transparency of coffee liquor as a guide.

When we talk about whether a thing is good or bad, we always make a comprehensive assessment from multiple angles or indicators. Take coffee for example, the aroma, taste, length of coffee, each is a cup of coffee is good or bad evaluation criteria. But there is no shortage of friends who will be unique, using the penetration of coffee liquid as an indicator to evaluate whether it is good or bad. For example, the clearer and cleaner the coffee liquid is, the better the coffee will be; the more muddy the coffee liquid is, the less delicious it will be. (the cleanliness of this article refers to the permeability of the coffee liquid.)

Generally speaking, what will be bound by this "standard" is black coffee. Because they will not have other materials that will affect the taste and appearance of coffee, this "indicator" is mainly aimed at black coffee groups. So, can the cleanliness of coffee liquid really be used as a criterion for evaluating the quality of a cup of coffee?

What affects the cleanliness of coffee? Qianjie's suggestion is that it is best not to judge the quality of coffee by vision, but mainly by taste. Because the cleanliness of coffee liquid is mainly determined by the way of coffee extraction and filtering equipment.

Some coffees look cloudy because the liquid contains certain insoluble substances. Oil, fine powder, are insoluble substances, when their existence reaches a certain amount, it will bring a dirty, turbid appearance to the coffee. For example, use coffee extracted from a pressure pot and American coffee in the Italian coffee system. This is because when these coffees are made, the utensils used cannot isolate some small insoluble substances, causing them to be added to the coffee liquid. And because these substances are too small to be completely caught by the human eye, they look like coffee is cloudy. But in fact, in the right amount of these substances will not have a negative impact on coffee, but will bring positive benefits, such as fine powder can make coffee more mellow, oil can make coffee more full aroma.

Take a simpler chestnut. Is the coffee made from hand-brewed coffee very clean and transparent?

But you know, this is the case where the filter apparatus is filter paper. The gap of the filter paper is very small, and the filtering performance is extremely high, so it can separate most of the fine powder and grease (not completely isolated, or will run out some), so the coffee is very clean. But when we replace the "filter paper" with "flannel filter cloth" or "metal filter screen", then because the gap in these utensils is too large, more fine powder and oil can seep out, and the coffee will be somewhat turbid. There is even an obvious layer of grease floating on the surface. So, will this make the coffee bad?

No, I won't! Because what controls whether the coffee is good or not is the quality of the beans and whether the extraction is reasonable. Therefore, Qianjie does not recommend making a decision on whether the coffee liquid is muddy or not. However, there is a situation in which we can see from the muddy coffee that the coffee may not be that good.

What is this situation? In addition to the filtration performance of the appliance will change the cleanliness of the coffee appearance, the coffee itself may also change the cleanliness. For example, when the coffee is just brewed, it is very clear and transparent, but with the passage of time and the decrease of the temperature, the coffee gradually becomes a little cloudy.

This is the condensation caused by a drop in temperature. Caffeine easily merges with chlorogenic acid, which becomes insoluble in water and then makes the coffee cloudy. The taste of cold coffee is well known and will not be so "close to the people", so when the quality of beans is not good, or the extraction is unreasonable, cold coffee will be very difficult to import. So in this case, some friends will develop the idea that turbid coffee is bad, which is understandable, but don't accidentally hurt the good coffee extracted in other ways.

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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 。