What Causes Coffee Cloudiness? Why Does Brewed Coffee Have Oils? Is Cloudy Coffee Safe to Drink?

Can Coffee Clarity Really Determine Quality?

When we discuss the quality of something, we always evaluate it from multiple angles or with various indicators. Take coffee, for example. The aroma, taste, and the length of the aftertaste are all evaluation criteria for a cup of coffee's quality. However, some friends might take an unconventional approach, using the transparency of the coffee liquid as an indicator to assess quality. For instance: the clearer and cleaner the coffee liquid, the better the coffee tastes; the cloudier the coffee liquid, the less enjoyable the coffee. (In this article, "cleanliness" refers to the transparency of the coffee liquid)

What Affects Coffee Clarity?

Generally, it's black coffee that gets constrained by this "standard." Because they don't have other materials that might affect the coffee's taste or appearance, this "indicator" primarily targets black coffee. So, can we really use the clarity of coffee liquid as an evaluation standard for a cup of coffee's quality?

FrontStreet Coffee's suggestion is that it's best not to judge coffee quality by visual appearance—tasting should be the primary method. Because the clarity of coffee liquid is mainly determined by the coffee's extraction method and filtration equipment.

Some coffees appear cloudy because they contain certain insoluble substances. Oils and fine particles both belong to substances that are insoluble in water. When their presence reaches a certain quantity, they give coffee a murky, cloudy appearance. For example, coffee extracted with a French press, or Americano coffee within the espresso system. This is because the equipment used in making these coffees cannot filter out some tiny insoluble substances, causing these substances to enter the coffee liquid. And because these substances are too small to be completely captured by the human eye, the coffee appears cloudy. But in reality, these substances, in appropriate amounts, don't negatively affect the coffee—on the contrary, they can bring positive enhancements. For example, fine particles can make coffee richer, while oils can make the coffee's aroma fuller~

The Impact of Filtration Methods

Let's take a simpler example: isn't coffee made by pour-over methods very clean and transparent?

But it's important to know that this is when the filtration device is paper. Paper filters have extremely small gaps and high filtration performance, so they can filter out most fine particles and oils (though not completely—some still get through), making the coffee very clean. However, when we replace "paper filters" with "flannel filters" or "metal mesh," the larger gaps in these equipment allow more fine particles and oils to seep out, making the brewed coffee somewhat cloudy, and even with a noticeable layer of oil floating on the surface. So, would this make the coffee less enjoyable?

When Can Cloudiness Indicate Poor Quality?

No! Because what determines whether coffee tastes good is the quality of the beans and whether the extraction is reasonable. Therefore, FrontStreet Coffee does not recommend making judgments about coffee taste based solely on whether it's cloudy or clear! However, there is one situation where we can tell from cloudy coffee that it might not taste as good.

Besides the filtration performance of equipment affecting the visual clarity of coffee, the coffee itself can also change its clarity. For example, when coffee is freshly brewed, it's very clear and transparent, but as time passes and the temperature decreases, the coffee gradually becomes somewhat cloudy.

This situation is the condensation phenomenon brought by temperature decrease. Caffeine easily combines with chlorogenic acid, and once combined, it becomes insoluble in water, which then makes the coffee cloudy. And as we all know, cold coffee doesn't taste as "approachable," so when the bean quality is poor or the extraction is unreasonable, the cooled coffee will be very difficult to drink. In this case, some friends might develop the idea that cloudy coffee doesn't taste good, which is understandable, but be careful not to mistakenly penalize delicious coffee extracted by other methods!

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