What The What is Bloom?
You may have read the term “bloom” in some of my other posts, but what exactly does that mean? Isn’t bloom a word associated with flowers? Well yes, but it is also associated with coffee. When it comes to coffee, the term bloom refers to the quick release of carbon dioxide that is a result of water coming into contact with fresh, ground coffee.
As mentioned before, when coffee beans are roasted, carbon dioxide is infused into the beans. Carbon dioxide helps protect and enhance the flavors and aromas of coffee. CO2 also plays a part in transferring flavor to cup. And, because coffee beans naturally degas, freshness is a very important factor. Proper storage is also very important, because oxygen quickens the rate at which coffee degasses.
So, if coffee needs CO2 to protect and to better transfer flavor, why is it necessary to bloom coffee, quickly releasing CO2? Well, when fresh coffee isn’t allowed to bloom, the quick release of gas essentially puffs up so much that it keeps the water from properly flowing through the grounds. Now, this is only an issue if you are using fresh coffee. Once the beans have lost too much CO2, because of the natural degassing process, the bloom will not occur. Thus, the bloom is actually a good indicator of freshness. Nevertheless, with fresh coffee, if the bloom affects the contact time between water and coffee, the extraction process can be negatively affected.
Therefore, allowing coffee to bloom prepares the coffee grounds for the possibility of proper extraction.
How to Let Coffee Bloom
Because the bloom occurs when water is introduced to fresh coffee grounds, this process is necessary for most brewing methods. Blooming naturally occurs in manual brewing processes, but letting it do so is what is debated. The most debated method is the French Press, because of the fact that it is an immersion method. Test it out, and see what you like better. Pourovers, though, have a limited time of contact with water, so letting that happen properly is important.
Anyway, a good rule of thumb for letting coffee bloom is to use two grams (1g = 1ml) of water for every gram of coffee. So, if you have 50 grams of coffee, like I suggested for the Chemex, use 100ml of water to properly bloom the coffee. The goal is even saturation, so if you do not use a scale, pour just enough to cover all the grounds. When done properly, the bed of coffee will not release very much brewed coffee until you actually start the pouring process.
After pouring in twice as much water as coffee, wait 30-40 seconds, so that it properly blooms, but doesn’t over-extract. If you let the blooming process continue for too long, the water that was poured into the brewing device can be in contact with the coffee grounds for too long, allowing over-extraction.