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What is the Pre-Soaking Stage When Brewing Coffee?

Pre-soaking is the "preparatory" step in coffee making. If the coffee is fresh, pre-soaking helps to pre-gas to stabilize the extraction and make the coffee taste better. In this article, we will explain why pre-wetting is done.

Pre-soaking or blooming is the rapid release of carbon dioxide that occurs when hot water hits ground coffee.

Pre-wetting is the brewing step before most of the water has passed. For pre-wetting, some water is poured into the ground coffee and waited for a while until it is completely saturated.

The volume of water for pre-brewing is calculated based on the ratio of 2-3 grams of water per 1 gram of coffee. So for a 15 gram serving of coffee, you need 30 grams of water for pre-soaking. Pre-soaking usually takes 30-40 seconds. When this time is up, the main stage of preparation begins - pouring water.

According to Maxwell Colonna-Dashwood, author of The Coffee Dictionary, pre-soaking measures the freshness of the roast, not the quality of the brew. And James Hoffmann, author of The Coffee Atlas, states that there is no scientific basis to substantiate the need for pre-soaking. However, some research shows that pre-soaking promotes the release of carbon dioxide and helps coffee brew better.

During the soaking process, the volume of ground coffee increases. This facilitates access to the solutes and the coffee oils rise to the surface. Pre-soaking helps stabilize the brewing process and improves extraction quality.

Why pre-wetting?

As a rule, pre-wetting is done during the preparation of freshly roasted coffee to artificially increase the degassing process, making the brewing process more manageable and the coffee more flavorful.

2-3 weeks after roasting, coffee actively releases carbon dioxide. When we grind coffee beans, the outgassing rate increases significantly due to the increased surface area of ​​the coffee. Then, when we pour hot water, the gas output increases even more.

Pre-wetting is necessary so that most of the gas is released before the main brewing phase begins:

If carbon dioxide remains in the coffee beans and participates in the extraction process, it forms carbonic acid when it comes into contact with water. This will make the coffee extremely acidic. Removing excess carbon dioxide results in a tastier glass.

The escaping carbon dioxide “repels the water” and interferes with the brewing process. Water can freely extract flavors and oils from coffee only after carbon dioxide has been released. However, the fact that the gas comes out of the coffee very quickly prevents even the water from coming into contact with the ground coffee. As a result, the extraction is uneven. To avoid this, you need to pre-soak.

The pre-soaking process is affected by water temperature, humidity, degree of roasting, hardness of the coffee bean, and source.

If the ground coffee does not foam during pre-soaking, most likely gas has already come out of the bean. As a rule, this happens for two reasons: stale coffee or due to improper packaging, in which the coffee is in prolonged contact with oxygen.


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