When we talk about coffee, we talk about a lot of things. There is coffee roasting, brewing, grinding and even storage. But what is this so-called coffee bloom that people talk about when brewing fresh roasted coffee?
What is the coffee bloom? When roasted coffee beans are made into grounds, the contained gasses are agitated and released more rapidly. And when very hot water comes into contact with these coffee grounds, they the gases are completely expunged, including carbon dioxide, and the infamous “bloom” is witnessed—a literal puffing up when the hot water hits and interacts with the grounds.
There is a lot to learn about the coffee bloom and I am really excited to discuss more about this topic in detail.
What is a Coffee Bloom?
If you find your coffee to be a bit lacking lately, or sour, or flat, you may think your equipment needs a vinegar rinse, but actually after that tried and true help, we encourage you to try a coffee bloom to be sure your coffee brew is reaching its highest potential in your cup.
Uninteresting, dull, flat, or even bad tasting coffee product can often be remedied through a remarkable and remarkably easy process that surrounds cool science with your coffee.
When heat is applied to organic substances, often there are chemical changes. In the case of heat mixing with coffee beans during roasting, carbon dioxide is discharged from the roasted coffee beans and then a natural loss of the carbon dioxide.
The roasted coffee bean maintains the carbon dioxide and other compounds within it, and over time, typically several days to a couple of weeks, the built-up gasses are released over time, also called “degassing”.
Using freshly roasted, ground coffee, you’ll be amazed at how much better your coffee result will be when you take a moment to use the simple coffee bloom technique.
Coffee Bloom and Releasing Gas
The coffee bloom is the glorious result of the rapid release of gas that is generated when very hot water interacts with coffee grounds, and which greatly enhances flavor of freshly roasted and recently ground coffee. Letting coffee bloom is easy and requires no additional equipment.
“Bloom” is a bit of an odd word that is now widely accepted to describe what is happening in a “coffee bloom”, but it does make sense once you see it happen. And more than that, the result of a coffee bloom is as lovely as a flower in its prime maturity in all its fullness and met potential, so we can go with that as well.
Fresh Flavor Released
Think of it like this: most of the flavor of a compounds of a coffee bean are contained in the carbon dioxide gases, and more gas equals more flavor. And not only that, but more gas also typically means fresher beans.
When beans have been sitting around over time, that means more time has elapsed for the beans to naturally release gases, so older beans are going to produce less gas and therefore a weaker bloom.
As the once-trapped gases are released by the hot water at a rapid pace, when pressure is applied to the outside to repel the water being pulled in, flavorful and texture-rich compounds are naturally extracted because the water pressure turbulence caused by exposing the coffee grounds.
Timing of the Grind and Degree of the Roast Matters
Keeping the volatile compounds of roasted coffee intact immediately after roasting and before the carbon dioxide is depleted can allow the potential for vibrant and flavorful coffee. Using freshly roasted coffee, inside of the first week of roasting, provides the best opportunity for a terrific bloom experience.
And since grinding roasted coffee beans quickly deteriorates the gas and compound, yet also increases the coffee surface area to cause a quicker reduction of gas, it’s important to try to delay grinding the beans until just before brewing use to ensure a proper and ideal coffee bloom setting.
The science of the gas is pretty cool, and helps us understand how allowing more carbon dioxide to escape just before brewing can improve the resulting fresh coffee flavor.
It’s really a two-fold situation:
- First, carbon dioxide is actually sour to our taste, so when grounds don’t bloom (or release the gas) before a brew, the held gas infuses our coffee with a sour taste.
- Second, carbon dioxide acts to repel water and so inhibits with coffee bean compound extraction during the brewing process.
Since hot water spontaneously extracts oils that translate to flavors and aromatics in our coffee, if carbon dioxide hasn’t had a chance to escape, the intended extraction of our brew is greatly limited. With both factors at work when carbon dioxide remains, there is both a sour taste and a limited extraction. Get that carbon dioxide out just before you brew.
Let your grind breathe to help capture all the intended qualities, notes, flavors and aroma!
Coffee Bloom and Other Flavor Factors
Not only does timing of the roast and the grind matter for the coffee bloom, but so does packaging and storage of coffee beans.
While airtight containers help to hamper the gases from escaping the beans quite as fast as a non-airtight container, the other perspective is one of one-way pressure containers with release valves where gases can escape the beans but no gasses can enter the container, much like a vacuum. Both methods have their benefits.
Besides packaging and storing the coffee beans, there are other additional factors that may affect the coffee bloom, such as storage temperature, storage humidity, hardness of beans, level of roast, and even origin of beans.
Think hotter temperature of coffee bean storage equating to more releasing of gas, so watch your storage temperature to help your coffee bloom when the time comes.
Humidity levels that are dryer also cause more gases to escape but be careful that you don’t have high humidity conditions for your coffee bean storage as high humidity leads to growth of fungus and molds. Finding a balance between high and low humidity is your best bet.
You may or may not have control over knowing your bean hardness factor, but it is helpful to keep in mind that the harder the coffee bean the denser the mass the gasses have to work their way through. The origin of your coffee beans affects their regional releases of gas as well.
Now, roast level is a factor you have lots of control over and which will play a significant role on a coffee bloom. Heavy, darker roasts result in more affected and oily beans which means there is far less releasing of gas.
They’ve undergone a longer roasting method and so contain more carbon dioxide, and so as a general rule: darker roast beans have larger blooms than lighter roast beans.
The Coffee Bloom Science
We can keep it simple like this: more gas means more flavor and fresher coffee; more gas means a bigger bloom, and a bigger bloom means more flavor and fresher coffee.
So, let’s get to the actual practical matters of how-to coffee bloom. There are some widely accepted basic techniques of the coffee bloom, and a few subjective tips and methods you can select based on your preference and desire.
Basically, you want to be adding hot water – very hot but not boiling – to coffee grounds to dampen them for a minute or two, prior to starting the featured extraction.
Specific How To of Your Coffee Bloom Technique:
For a coffee ground Pour Over Bloom, start by pouring, slowly and in a circular motion starting at the outer perimeter of the grounds and working inward, six to twelve teaspoons of very hot but not boiling water over the coffee grounds.
This process helps ensure the grounds are soaked evenly but aren’t drenched. Leave this alone for one minute, and then begin your regular process to complete your coffee extraction.
For a French Press Bloom, be sure to use a course grind of coffee bean grounds and slowly pour about three to six teaspoons of very hot but not boiling water over the coffee grounds. Foam on top of the water should start to form right away which is your bloom!
Allow the bloom to sit for 20 seconds and then stir it with a spoon to ensure the water has interacted with all the grounds in the bloom. Then begin your normal brew process of three to four minutes steeping.
For more information on brewing coffee with a French Press check out my post
Automatic Drip Coffee
For an Automatic Drip Coffee Maker Bloom, using a filter of good quality so that your brew will be both appropriately strong and properly flavorful, pour just enough hot but not boiling water to soak but not pour through the freshy roasted and ground coffee beans.
Let the grinds acclimate to the water soak for about one minute, give or take. Then begin your normal brew process. Because of the pre-soak, you’ll notice that the water stands on top of the grounds and then soaks through slowly, providing more extraction that results in better a better coffee result.
Experimenting with different roast levels and soak times will help you find what works best for your flavor palate. If your coffee isn’t blooming well, you may have over-roasted (or old and stale) beans as a first cause to explore as the explanation.
Make Sense? Then Try It and Share Your Results
Perhaps you’re still wondering why it’s called “blooming”? Well, the hot water quickens the releasing of still held carbon dioxide, and that’s what we see with the bubbling up from the hot water of released gas when water first contacts the roasted coffee grounds.
Make sense? It will when you witness your own coffee bloom. Once you experience the simplicity of producing your own coffee bloom, share your results with others so they too can enjoy coffee at its best potential.