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 tend to evaluate it from multiple angles or with several indicators. With coffee, for example, the aroma, the taste, and the length of the aftertaste are all criteria for a cup's quality. Some friends, though, take an unconventional approach and use the transparency of the coffee liquid as a gauge. The clearer and cleaner the liquid, the better the coffee, they reason; the cloudier the liquid, the less enjoyable the cup. In this article, "cleanliness" refers to the transparency of the coffee liquid.

What Affects Coffee Clarity?

Generally, it is black coffee that gets constrained by this standard, because it has no other ingredients that might affect taste or appearance, so the indicator mainly targets black coffee. Can we really use the clarity of the liquid as an evaluation standard for a cup's quality?

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

Some coffees appear cloudy because they contain certain insoluble substances. Oils and fine particles are both insoluble in water. When their presence reaches a certain quantity, they give the coffee a murky, cloudy appearance. Coffee extracted with a French press, or an Americano from the espresso system, is a good example. The equipment used for these coffees cannot filter out some tiny insoluble substances, so those substances enter the liquid, and because they are too small for the human eye to capture completely, the coffee looks cloudy. In appropriate amounts, these substances do not negatively affect the coffee; on the contrary, they can bring positive enhancements. Fine particles can make coffee richer, while oils can make its aroma fuller.

The Impact of Filtration Methods

Take a simpler example: is coffee made by pour-over not very clean and transparent?

It helps to know that this is true when the filtration device is paper. Paper filters have extremely small gaps and high filtration performance, so they filter out most fine particles and oils, though not completely, since some still get through. That makes the coffee very clean. When we replace paper with a flannel filter or a metal mesh, however, the larger gaps in those devices let more fine particles and oils seep through, making the brewed coffee somewhat cloudy, sometimes with a noticeable layer of oil floating on the surface. Does that make the coffee less enjoyable?

When Can Cloudiness Indicate Poor Quality?

No. What determines whether coffee tastes good is the quality of the beans and whether the extraction is reasonable. FrontStreet Coffee therefore does not recommend judging coffee taste based only on whether it is cloudy or clear. There is, however, one situation in which cloudy coffee does tell us 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. When coffee is freshly brewed it is very clear and transparent, but as time passes and the temperature decreases, it gradually becomes somewhat cloudy.

This is the condensation that comes with a drop in temperature. Caffeine easily combines with chlorogenic acid, and once combined it becomes insoluble in water, which makes the coffee cloudy. As we all know, cold coffee does not 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 that case, some friends may conclude that cloudy coffee does not taste good, which is understandable, but be careful not to penalize delicious coffee extracted by other methods.

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FrontStreet Coffee Recommendation

If you want to see how much oils and fine particles can contribute to a cup, the French press is the clearest demonstration. It is a full-immersion brewer with a metal filter, so the water and grounds steep together directly and the resulting coffee keeps more oils and has a heavier, fuller body. Anyone who dislikes grounds or fine particles in the cup may not enjoy it, but for richness it is unmatched. Because the French press is an immersion method and the grounds stay in contact with hot water for a long time, a light roast would extract too much acidity and mask its florals and light layers, so a medium or dark roast generally suits it better and expresses sweetness and caramel notes more clearly.

For a clean, aromatic cup, FrontStreet Strawberry Candy is a good match. This Geisha blend is made from a honey-processed Costa Rican coffee and a washed Panama Geisha, combining the finest flavors of Central America; steeped in a French press it gives off rose, citrus, grape, and dried blueberry aromas, and with milk it tastes of strawberry candy. For a low-acid, oil-rich black coffee, FrontStreet PWN Golden Mandheling is the first choice. As one of Asia's most famous specialty coffees, it is sorted three times by hand and once by machine, so the beans are even and bright. Medium-dark roasted, it has large beans and rich spice, caramel, fir, and dark chocolate aromas, and a French press brew is full-bodied with a good crema.

On grind, FrontStreet Coffee suggests a coarse setting about the texture of granulated sugar: EK43s setting 10.5 on an electric grinder, or 26 on a hand grinder, closer to small gravel than fine sand. Grinding too fine lets the water extract too quickly, and with a French press in particular, fine particles can pass through the metal filter and leave a lot of sediment. If you want more layered flavor you can grind finer, but remember to shorten the steeping time to avoid over-extraction. For the ratio, the common formula is 1:15, that is 15 g of coffee to 225 g of water, which extracts to a concentration of 1.1-1.2% and a thicker, fuller cup; start there and adjust the coffee or water to taste. Without a thermometer, let boiled water rest for 2 to 3 minutes, adjusting for the weather, to brew at about 90 °C, or use a temperature-controlled kettle or a thermometer. Because a French press pours all the water at once and has no stirring to raise extraction during the steep, you may need to raise the water temperature by 1 to 2 °C above a normal pour-over to compensate. Steeping time usually falls between 3 and 5 minutes; 5 minutes may be too long for a darker roast and turn it bitter and astringent, while 3 minutes may be too short for a light roast to release its flavor, so FrontStreet Coffee suggests starting with 4 minutes. To brew, remove the filter assembly, add the ground coffee, pour in 15 times its weight in hot water, stir gently, and seat the plunger without pressing. After 4 minutes, press the plunger slowly to the bottom and pour the coffee out carefully, without disturbing the grounds at the base.