All About Coffee Bloom

Coffee has been enjoyed by the masses for a very long time. It is however, only in the decade or so that drinking coffee has become very hip. But I like to look deeper into everything that interests me and generally ignore trendy activities. Coffee is obviously one of my life’s top interests, and drinking it is a lifestyle, not a trend. But the recent coffee trend is something I welcomed with an open mind. I started to network with young coffee amateurs who  have a new found obsession with the different brewing techniques and achieving perfection when brewing coffee. The traditional drip brew coffee maker is now supplemented with pour-over cups, French presses, Aero presses and other upper tier coffee makers in most homes. The importance of  coffee bloom is now a topic I often share when discussing the art of brewing the perfect cup. I find it is all too often overlooked in favor of coffee making devices.

What Exactly is Coffee Bloom Anyway?

The roasting of coffee beans initiates chemical reactions that release gases inside the bean. These gases, mostly carbon dioxide, are trapped inside. Statistics show that after roasting, around 1 to 2% of the bean’s mass is actually CO2.

Once the process of roasting is completed, the gases start to escape the beans. This is known as degassing and it continues for up to two weeks after roasting. Initially the gases escape so fast that if the beans are used during this initial degassing period, it does not yield a very good cup of coffee as the extraction in this stage is very uneven. This is why roasters do not begin selling the freshly roasted beans immediately, but hold off sale for up to one week while the beans degas.

Typically roughly forty percent of the carbon dioxide leaves the bean in the first twenty-four period. While degassing continues over time, its speed slows down. So do we wait to brew coffee until all of the CO2 has exited the bean? Well not quiet. The problem is that a lot of those amazing flavors of coffee that we love so much, are packed inside the CO2 and when it leaves so does all the good taste and freshness of coffee! If all of the CO2 exits, the coffee becomes flavorless and stale so we definitely want to retain a certain degree of CO2 to hold on to the freshness, aroma and flavor of the coffee.

Now this is where bloom comes in. When those initial drops of water hit the grounds to start the brewing process, the CO2 that remains inside the bean is expunged. It can be seen bubbling out while the grounds expand and the process of extraction begins. Blooming is the action of making the bed of coffee grounds moist so any remaining carbon dioxide can evaporate and the water you add after blooming is completed, can extract the flavors from the coffee evenly.

Is There a Correct Way to Bloom?

Blooming is simple and does not require any special equipment. The key to blooming correctly is knowing not to put so much water on the grounds that it begins to drip prematurely. Start pouring the water in the middle of the grounds and work your way outward in circular motion until all the grounds are moistened. Do not let the water touch the filter paper as it might cause tunneling. As soon as water hits the grounds you should see thick, foamy bubbles form on top of the grounds. Once the bloom is completed, that happens when the bubbling stops, continue with the brewing process as normal.

A good rule to follow for estimating the amount of water needed to bloom coffee is to take the mass of coffee grounds and use double the mass of water. So for one gram of coffee grounds, use two grams of water to bloom. Allow the grounds to bubble for approximately thirty or forty seconds.

Why Bother Blooming?

Blooming coffee will enhance the flavour of your beverage. Carbon dioxide has a sour taste, if the coffee is not bloomed that sour taste with infuse in your cup. Furthermore, carbon dioxide occupies space in the coffee grounds if the gas is not removed, water will not be able to enter the spots which are occupied and carry out an even extraction.

What if There is No Bloom?

If you do not see any bloom, chances are that the coffee grounds you are using have already degassed and the compounds that give coffee its good taste have depreciated. Hence, your brew will not be as flavorful as it could have been. This typically happens when the coffee is not fresh or the bag in which it was stored was not sealed properly and gases escaped through the bag. This is why it is best to grind the beans just before brewing. Grinding increases surface area, which gives the carbon dioxide more place from where to escape thereby by increasing speed of degassing.

It must be remembered different kinds of coffees tend to bloom by different amounts. This is due to differences in roasting. Dark roasts bloom more than lighter ones because the longer roast times to get the dark color means greater quantity of carbon dioxide was also produced. So the amount of bloom is not a necessary indicator of freshness.

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