How to Handle Moist and Clumpy Coffee? Can You Still Drink Damp Coffee???

Regarding the phenomenon of oil on the surface of coffee beans, FrontStreet Coffee has noticed that coffee beginners have various questions about it:

"Why are the coffee beans wet? I just opened them."

The coffee beans are oiled up, they must have been stored for a long time, right?"

The surface of these coffee beans is so oily, could they be spoiled?"

The "oil" on the surface of coffee beans is essentially the water-soluble fat of the beans.

Before roasting, green beans have a tight structure with oils wrapped around the fibrous matrix. During the roasting process, the roaster provides a large amount of thermal energy to the coffee beans, causing the internal structure to continuously expand, which further opens up the pores in the cell walls of the green beans, storing large amounts of carbon dioxide. As the roasting degree deepens, when roasting is complete and the coffee beans return to normal temperature and pressure, these carbon dioxide gases begin to slowly release, simultaneously allowing fats to penetrate and adhere to the bean surface.

Effect of Roasting Degree

The phenomenon of oil emergence is generally seen in coffee beans roasted to dark levels or higher, that is, around the second crack, where oils gradually seep to the surface along with the gases. Freshly roasted dark beans will have a slight sheen of oil, and by the next day, carbon dioxide begins to release more rapidly, emitting roasted aromas of caramel, dark chocolate, and more.

Like FrontStreet Coffee's Indonesian Gold Mandheling coffee beans, which are roasted to a medium-dark level, they will develop an oily sheen after 3-5 days of degassing, which is a normal phenomenon. During the optimal flavor period, some coffee beans about 5-7 days after roasting will develop dot-like oil droplets on the surface. This is caused by local dehydration due to uneven heating, and these dot-like oils actually represent the best flavor period for the coffee.

Therefore, oil emergence is only one simple criterion for judging the roasting depth of coffee beans and has no necessary relationship with coffee freshness. For extremely dark roasts like "Japanese dark roast coffee," oil emergence begins on the first day after roasting while still in the package, and soon the coffee beans present a dark, glossy appearance.

Signs of Moisture in Coffee Beans

If coffee beans are affected by moisture, they generally won't present a "wet" appearance, and it's difficult for us to directly determine whether roasted beans have been affected by moisture through visual observation. However, we can judge through the signs that coffee exhibits during the brewing process.

Freshly roasted coffee beans have very low moisture content, about 1-2%. If stored in a humid environment, coffee beans will act as moisture absorbers, leading to increased moisture content and subsequent spoilage and mold. Common phenomena include grinding resistance, clumping of coffee powder, loss of aroma, and appearance of moldy smells.

How to Determine if Coffee Beans Are Fresh?

The most common packaging for coffee beans includes one-way valve sealed bags and vacuum-sealed containers, which can isolate coffee beans from moisture molecules in the air. Additionally, the carbon dioxide released by the beans themselves acts as a protective gas, enveloping the coffee beans and thus slowing down the dissipation of coffee flavors. Once the packaging is opened, the oils will contact moisture in the air and undergo oxidation reactions, accelerating the aging of coffee beans.

Some medium-light roasted coffee beans, when left for a period of time, will develop a layer of oil on the entire surface of the beans. They smell weak in aroma and have a slightly greasy smell, indicating that a significant portion of the flavor has been lost, and they should be consumed as soon as possible.

Freshness is most apparent during the extraction process. For example, during blooming, if the coffee grounds layer doesn't expand at all, it indicates that the gases in the coffee beans have been completely released. Throughout the entire extraction process, no aroma is released, the taste is empty and bland, and it has a woody fibrous flavor when consumed.

The main factors affecting coffee bean freshness are oxygen, moisture, light, and heat. Therefore, to properly store coffee beans, they need to be unground, sealed, protected from light, moisture, and kept at low temperatures. Even if these conditions are met, the flavor of coffee beans will gradually dissipate over time. Therefore, compared to long-term storage, FrontStreet Coffee still recommends enjoying them during their optimal flavor period.

Important Notice :

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FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473