If you are a true-blue coffee aficionado, or if you frequent coffee shops, the term “coffee bloom” would probably be in your vocabulary by now. Otherwise, let us increase your coffee knowledge by understanding one of the important phases in coffee brewing: coffee bloom. Do take note that this is applicable in a pour-over setup with ground beans, but not in ESE pods or Nespresso capsules.
When coffee beans are roasted, the heat causes carbon dioxide to become locked inside of the beans. Once the roasting process is completed, the beans then begin to slowly discharge these gases in a process known as “degassing.” Blooming, on the other hand, is a process of almost entirely releasing these carbon dioxide gases and several other oils and compounds. The bloom usually looks like a foamy layer above the ground coffee when hot water is poured on it.
When hot water touches the ground coffee, the outgassing CO2 presents a pressure barrier to it, which means that the water cannot fully penetrate the coffee grounds immediately. Simply put, the coffee bloom is like the scenario on a Black Friday. If you put up a ‘95% Off Sale’ promo at the same moment there was a panicky fire drill, people outside would scramble to get in while the ones already inside would scramble to get out, and you could have a mess on your hands. That is unless people outside waited until everyone got out.
If you just pour in one go the entire amount of water necessary for our desired brew, the outward pressure of the gasses makes full contact with the water and coffee difficult, and we can’t get a complete flavour extraction. By primarily wetting freshly roasted and freshly ground coffee with hot water, we can trigger the outgassing and treat ourselves to a beautiful coffee bloom show. After at least a minute, a significant amount of CO2 has been released, so that when we pour the rest of our water, it can make complete contact with the ground coffee beans.
Another reason why we should bloom coffee is to remove some of the acids. Acids do make coffee taste great, but not all acids work to our advantage.
If the carbon dioxide in the coffee beans is not allowed to degas and become trapped during the extraction process, the gas and water will form carbonic acid. Carbonic acid has a sour taste, and if you have ever tasted flat carbonated water, you know it isn’t a yummy kind of sour taste.
Blooming also releases some of the other tastier acids such as malic and citric acid, but carbon dioxide is released much sooner in the blooming process.
Carbonic acid in your coffee is not totally bad, but it is better to remove the excess CO2 from your java.
Now that you know a little more of the science behind coffee bloom, you can now start to brew a better-tasting cuppa with the coffee beans, right in the comfort of your own home.