As you continue your journey with brewing coffee, you will notice the word ‘bloom’ or ‘blooming' pop up in all methods. I’m hoping to give you a little insight into what blooming is and why it needs to be done.
What is Blooming?
To keep it as simple as possible, blooming is the fast release of gases (in particular, carbon dioxide) that occurs when hot water comes into contact with the coffee grounds.
When we roast coffee, the heat causes gases to be trapped inside the bean. It is only when the roasting process ceases that the bean begins to gradually release carbon dioxide along with other volatile compounds.
Coffee beans will continue to release the carbon dioxide over a long period of time. However, this process is accelerated when you grind your coffee or add hot water to the ground coffee. When hot water comes into contact with ground coffee, it immediately releases most of the carbon dioxide creating what we know as the ‘bloom’. The majority of a coffee bean's flavour compounds are trapped in the carbon dioxide.
Carbon dioxide tastes a little strange, so blooming purges out those gases, which we don’t want in our coffee, and allows the brew to extract properly and release the flavour compounds.
OTHER VARIABLES AFFECTING THE BLOOM
- How you store your beans - storing your beans in a hot place will release gases quicker (so it's best to store them in a airtight container in a cool dark place).
- Bean hardness - harder beans means more density for the gas to make its way through.
- Roast levels/style - roast level will have a significant influence on bloom. Extremely dark roasts have a much smaller amount of gases compared to a light roast.
- Origin - different climate, soil, process, varietal.
How to Bloom?
I start pouring into the centre of the ground coffee bed, working my way towards the sides. Ground coffee can hold approximately double its weight so I normally pour twice the amount of water to ground coffee. If the coffee is very fresh, extend your bloom time to about 45 seconds to 1 minute. Generally, I bloom for about 30 seconds. We are trying to let the grounds soak up all the water without the water coming through. You will notice the coffee bed rising up. This is the carbon dioxide releasing from the coffee. Once you have waited, continue with your method.