Why Does Coffee Taste Salty? What Causes Salty Flavor in Brewed Coffee? What Are the Signs of Under-Extracted Coffee?

Sourness, sweetness, and bitterness are the three most common flavors we encounter in a cup of coffee. Because these three flavors are crucial to the composition of coffee, many articles often revolve around them. However, besides these three flavors, coffee actually contains another hidden flavor—saltiness.

Saltiness has always existed in coffee, primarily originating from minerals contained within coffee beans themselves, such as cyanide, bromide, iodide, nitrates, sodium, magnesium, calcium, and other inorganic substances. However, due to its relatively low proportion, it is often masked by other flavors, making it difficult for people to detect. Therefore, compared to the first three flavors, the presence of saltiness is more like that of a默默付出的后勤角色 (dedicated support staff), as its existence helps enhance coffee quality! In the article "Does adding salt to coffee make it sweeter?" FrontStreet Coffee shared that because flavors exist in a mutually balancing relationship, adding an appropriate amount of salt to coffee can enhance sweetness, reduce bitterness, and improve richness. The saltiness naturally contained in coffee serves the same function. However, this has a prerequisite: the saltiness must be present in appropriate amounts and remain undetectable to people.

The reason why people often don't deliberately emphasize the presence of saltiness is that as long as there are no extraction problems and the beans are of good quality, the saltiness, as mentioned above, is difficult for people to detect. If we can clearly taste saltiness from a cup of coffee, it's highly likely that there's a quality issue with this coffee. The cause could be either extraction and brewing, or it could come from the beans themselves. Therefore, today, FrontStreet Coffee will share what specific reasons might lead to detecting obvious saltiness in coffee!

I. The Impact of Coffee Bean Growing Environment

As is well known, when coffee is grown at higher altitudes, the coffee plants slow down their growth due to low temperatures, while simultaneously generating more substances internally to resist the cold, including sugars, which contributes to the formation of high-quality flavors. However, when coffee is grown in low-altitude areas, the growth rate of coffee tends to be normal, without deliberately generating organic acids and sugars to resist extreme environments. Naturally, there won't be excessive sour and sweet flavors to mask the saltiness.

Besides altitude, factors during the growing period such as fertilizer use, sunlight duration, and rainfall amount all influence the accumulation of substances in coffee. When fewer substances that can form sour and sweet flavors are generated, the proportion of saltiness in the coffee will relatively increase. When we brew such coffee beans, we will naturally be more likely to bring out the saltiness.

II. The Impact of Defective Beans

Before and after roasting, if the roaster doesn't screen out defective beans, the presence of these defective beans might lead to obvious saltiness in the brewed coffee. Among various defective beans, those that cause coffee to easily develop saltiness are "underripe beans," also known as "quaker beans."

Quaker beans are coffee beans obtained when coffee cherries are harvested and processed before they are fully ripe. Because they are harvested while unripe, the organic acids in the coffee have not been converted into sugars. And sugars are important components that generate rich aromas and flavors during the roasting process. Therefore, underripe beans that have not completed this conversion cannot produce rich aromas and flavors after roasting, instead showing more grassy, harsh acidity, and astringent sensations—reminiscent of undercooked food.

When a certain amount of quaker beans is mixed with other normal ripe beans and brewed together, these quaker beans will drag down the flavor performance of the entire cup of coffee, making the brewed coffee more likely to have obvious saltiness. Therefore, before and after roasting, roasters must strictly screen for defective beans, with quaker beans being just one type among them.

III. The Impact of Extraction

This is the most frequent link that causes saltiness to appear in coffee—extraction. When making coffee, if parameters or brewing methods are improper, leading to under-extraction or excessive concentration, we will most likely be able to taste saltiness from the coffee. This is because sweet and bitter substances have not yet fully dissolved, and at this point, the quantities of sour, sweet, and bitter flavors in the coffee are insufficient to mask the presence of saltiness. Therefore, during under-extraction, saltiness is easily detected and felt by people.

Excessive concentration, on the other hand, is due to flavors being too concentrated, causing our taste buds to be unable to distinguish individual flavors, so they package everything together and send it to the brain. At this point, the saltiness we perceive is actually an illusion created by the excessive concentration of flavors.

So how can we distinguish which situation is causing the saltiness? It's very simple—we just need to dilute the coffee liquid by adding additional water. If the saltiness disappears after adding water, it means it was an illusion caused by excessive concentration; if the saltiness still exists after dilution with water, then it's due to under-extraction, and we need to adjust extraction parameters to improve extraction efficiency. (Of course, it's not excluded that both under-extraction and excessive concentration might occur simultaneously~) Generally, cases where saltiness appears due to under-extraction are most common, mostly concentrated in brewing of high-density, light roast coffee beans and beans that haven't been properly aged. Because these beans are relatively harder to extract, they more easily lead to under-extraction and the appearance of saltiness.

For brewing high-density, light roast coffee, we can move on to learn from this article "How to brew light roast coffee beans?" As for overly fresh coffee beans, FrontStreet Coffee suggests letting them "rest" for a few days, waiting until the carbon dioxide content no longer excessively affects extraction before brewing~

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