What Does it Mean to Allow Coffee to Bloom? Barista Explains


Blooming is a way of enhancing the flavor of your coffee. This is an easy task that would not require you to have any additional equipment, and you can do it within a matter of seconds.

To allow coffee to bloom means letting recently roasted and ground coffee loses carbon dioxide and other gasses when brewing. Coffee beans contain carbon which reacts with oxygen when roasting to form carbon dioxide gas. The gas slowly escapes on its own through a process called degassing, which takes about two weeks. 

Dampening ground coffee speeds up the rate at which it loses carbon dioxide. A foam with bubbles called bloom forms on the surface of the powdered coffee as the gas escapes, which takes 35-40 seconds. It may take longer than 45 seconds or shorter than 25 seconds depending on prevailing factors such as the type of beans and freshness. 

What is the Purpose of Coffee Bloom?

Coffee bloom helps minimize carbon dioxide in the coffee grinds. You may wonder why it is necessary to lower the gas amount or completely do away with it. Here are some benefits of coffee bloom:

Is An Expensive Coffee Grinder Wort... x
Is An Expensive Coffee Grinder Worth It
  • It enhances the flavor of coffee in your brew. The acidic carbon dioxide gas has a sour taste, and when it dissolves the hot water, it makes the whole cup of coffee taste sour. 

You don’t want a bitter/ sour tasting cup of coffee, and allowing the gas to escape restores the pleasant chocolatey taste of coffee. 

  • It allows water to extract nutrients from the coffee grind. Caffeine, tannin, proteins, carbohydrates, and oils are some of the chemical components of coffee beans. 

Carbon dioxide on newly roasted berries hinders water from dissolving the chemicals in coffee, which degrades its taste. When the gas escapes, water penetrates the berries extract and dissolves the nutrients.

  • It releases the tasty aroma of coffee. Then, as carbon dioxide gas escapes, it comes along with the sweet aroma from the berries that stimulates your nervous system while preparing.

Does Coffee Bloom Matter?

Coffee bloom is essential. As mentioned, blooming is an easy process, and so it matters in many ways that include the following:

  • It helps you detect the quality of coffee you are using. The amount of CO2 evolved as coffee blooms indicate its freshness. Recently roasted coffee gives off more gas than one with a long shelf life. 
  • It improves the flavor of the coffee. Coffee bloom allows water to infuse the essential nutrients in coffee and dissolve them, making your brew tasty and stimulating to your muscles.
  • It improves the nutritional value of coffee powder. Once CO2 escapes, the water interacts with ground coffee drawing all the essential nutrients such as caffeine, oils, and proteins.
  • It helps you estimate the amount of CO2 in coffee by observing the flow of bubbles and the size of foam formed.
  • It helps you to distinguish stale coffee from fresh coffee. Stale coffee liberates little or no gas, while fresh coffee gives out a steady gas stream when you let it bloom.
  • It lowers the amount of gas in your beverage, relieving you from too much gas and discomfort after taking it.
  • It reduces bitterness in coffee caused by acidity when carbon dioxide dissolves in water.

What Does a Coffee Bloom Look Like?

Coffee bloom has a frothy light brown appearance with a steady flow of bubbles whose intensity decreases with time. The foam is formed by a buildup of gas on the surface of ground coffee interacting with water molecules. The gas escapes as a continuous stream of bubbles.

After wetting your coffee grind, the froth swells for the first thirty seconds and flattens down as the bubbles burst from escaping gas. 

As the gas diminishes, the powdered coffee darkens and restores its original dark brown shade. 

The particle size of the grind increases as it blooms due to degassing and popping on the surface as you add hot water.

Should You Bloom Pre Ground Coffee?

You can bloom preground coffee, but the taste may not be as fruity and chocolatey as self-ground coffee. 

Once you roast coffee, the carbon and other organic substances combine with oxygen from the air to form CO2 gas, the gas slowly escapes, and within two weeks, there can only be a few traces remain. 

The flavor, scent, and freshness of preground coffee cannot match that of self-ground coffee because when you allow it to bloom, there is minimal water interaction with the coffee powder.

Also, the aroma that comes with the escaping gas is weak and lacks that calming effect on your nerves as you brew a cup of your favorite beverage.

One benefit of using preground coffee is its convenience. If you are not good at grinding or lack the equipment to do so, you are better off purchasing ground coffee and saving yourself the hassle of crushing the beans. It also saves time. 

How Long Should You Let Coffee Bloom?

The ideal time to let your coffee bloom is 35-45 seconds for freshly roasted and ground berries. 

Unfortunately, the period decreases fore-grounded coffee with a shelf life that exceeds two weeks since most of the gas will have escaped naturally. 

For coffee beans roasted and ground within the last 24 hours, the bloom time should be longer than one minute because of the high quantity of gas in the grinds.

 Other factors to consider when setting bloom duration include:

  • The temperature of the water. Carbon dioxide diffuses and escapes faster at a high temperature (hot water) than at a low temperature (cold water).
  • The intensity of roast. Darker, heavily roasted coffee berries contain more gas than the brown lightly roasted ones. The darker ones require more bloom time than less dark ones.
  • Amount of moisture in the air. Coffee degasses rapidly in dry areas than in humid areas. To contain the gas in berries after roasting, you should keep ground coffee in containers that keep it humid. 
  • Bean texture. Coffee beans with a hard surface require a long bloom time as the gas takes longer to penetrate the hard surface and escape.
  • Quantity of coffee. A small amount of coffee grind loses gasses faster than a large amount.
  • Type of beans. Different types of coffee beans take varying lengths of time to degass. The bloom time for coffee that degasses faster is shorter.

How Much Water Do You Use For Blooming Coffee?

When blooming, the amount of water you should add to coffee is small, just enough to make the grinds wet and trigger the gasses to escape. 

The standard ratio of water to coffee in grams is 1:3, though you may adjust the ratio depending on the type of beans.

Suppose you want to brew 10 grams of coffee; you should add about 30 grams of water to the grind and allow it to bloom before you continue brewing.

There are over 100 species with different features such as texture, grain size, and water absorption rates. Therefore, the amount of water you should add to your ground varies from one type to another.

Other factors that influence the amount of water include:

  • The extent of roast. Beans that are roasted lightly require more water to bloom, while those with extended roasting bloom with less water.
  • Humidity. Coffee grinds stored under humid conditions bloom with a small amount of water, while those stored under dry conditions require more water.

The ideal humid condition to store coffee is average to avoid mold infestation at high humidity and loss of flavor in dry conditions.

  • Freshness. Freshly roasted and ground coffee has a lot of gasses and requires more water for blooming, unlike one with a long shelf life which has already lost most of its gas buildup.
  • Size of coffee grinds. Fine coffee particles take longer to soak in water and require more water for blooming, while coarse particles soak faster and require less water.

How Long Should French Press Bloom?

Ideally, French press blooms should last between 25-40 seconds. You can adjust this time to suit your taste and give you the best results depending on the type and quality of your grind. 

If you are using fresh coffee berries that have undergone extended roasting, blooming will take longer because the concentration of CO2 in the grinds is high.

Here are some factors to consider when setting bloom time for French Press.

  • Amount of coffee you are brewing. Large quantities require more bloom time.
  • Type of coffee. Arabica coffee blooms faster than Robusta coffee and therefore requires less time.
  • Shelf life- coffee grinds with longer shelf life require less time to bloom since they have a limited amount of gasses.
  • The water temperature- Hot water drives CO2 faster and blooms coffee robustly, unlike cold water, although the latter is not ideal for blooming.
  • Coffee grind texture. Finely ground coffee takes a long time to dampen all the particles, hence a longer bloom time.

Final Thoughts

Lastly, the other factor to consider is the roast extent. The volume of carbon dioxide on deeply roasted coffee beans is higher than the lightly roasted ones. This is because the former requires more bloom time to emit the gas buildup fully.

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