Why do deep-roasted coffee beans produce oil? can you still drink them? How to deal with the damp of hand-washed coffee beans

With regard to the phenomenon of oil coming out from the surface of coffee beans, Qianjie noticed that coffee novices had all kinds of questions about it:

"Why are the coffee beans wet? It's new. "

"the coffee beans are out of oil. It's been kept for a long time."

"Coffee beans are so oily on the surface, could they be broken? "

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

The raw beans before baking have a tight structure and fat wrapped in the fiber matrix. During the roasting process, the bean roaster provides a lot of heat for coffee beans, and the structure in the beans continues to expand, resulting in further opening of the stomata in the cell wall of raw beans, storing a large amount of carbon dioxide. As the degree of baking deepens. When the baking is finished and the coffee beans return to normal temperature and pressure, the carbon dioxide gas begins to be discharged slowly, while the fat is permeated and attached to the bean surface.

The influence of baking degree

The phenomenon of oil production is generally reflected in the deep roasting of coffee beans, that is, before and after the second explosion, the oil gradually seeps out of the surface with the gas. Fresh deep-baked beans will be slightly oily, and the next day carbon dioxide will begin to accelerate, emitting caramel, black and other baking aromas.

Like Qianjie Indonesia gold Mantenin coffee beans belong to the middle depth of roasting, raising beans for 3 to 5 days will be glossy, is a normal phenomenon. In the taste stage, some coffee beans about 5-7 days after roasting, there will be dotted oil droplets on the surface, which is due to uneven heating and local dehydration. These dotted oils represent the best taste period for coffee.

Therefore, oil production is only one of the bases for simply judging the roasting depth of coffee beans, and it has nothing to do with the freshness of coffee. If the deep-roasted "Japanese-style deep-roasted coffee" has just been roasted, the oil begins to come out on the first day in the package, and the coffee beans will soon show a dark and bright appearance.

The performance of coffee beans exposed to moisture

If coffee beans are damp, they generally do not show a "wet" appearance, and it is difficult for us to directly judge whether the cooked beans are damp or not by the naked eye, but we can judge by the signs shown in the brewing process.

Freshly roasted fresh coffee beans have a low water content, about 1: 2%. If stored in a humid environment, coffee beans will become a hygroscopic agent, resulting in higher water content, and then deterioration and mildew. The common phenomena are stutter, coffee powder caking, aroma loss, mildew smell and so on when grinding particles.

How to judge whether the coffee beans are fresh?

The most common packaging of coffee beans, one-way exhaust valve sealing bags and vacuum sealed cans, can isolate coffee beans from water molecules in the air, and the carbon dioxide released by itself acts as a protective gas, wrapping coffee beans, thus slowing down the dissipation of coffee flavor. Once unpacked, the grease will come into contact with water vapor in the air to form an oxidation reaction, accelerating the aging of coffee beans.

Some medium and shallow roasted coffee beans were placed for a period of time, the whole coffee bean surface covered with a layer of oil, smell weak, but also with a hint of greasy flavor, indicating that a large part of the flavor has been lost and needs to be drunk as soon as possible.

Freshness is the most obvious in the extraction process, such as stewing, the powder layer does not expand at all, indicating that the gas of coffee beans has been exhausted. There is no aroma released in the whole extraction process, the taste is empty, and it tastes like wood fiber.

The freshness of coffee beans is mainly affected by oxygen, moisture, light and heat, so if you want to preserve coffee beans properly, you need to meet the requirements of unground, sealed, light, moisture and low temperature. Even if the above conditions are met, the flavor of coffee beans will gradually dissipate over time, so Qianjie is recommended to enjoy it best during the taste period rather than keeping it for a long time.

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