Blooming Coffee - Why The Bloom is Important

What is the coffee bloom?

During the roasting process, there are certain reactions that take place inside the coffee bean that transform it from a fairly tasteless pip (it's not really a bean, but the seed of the coffee cherry) into the wonderful coffee flavour that we know and love today.

A by-product of this process is the production of Carbon Dioxide inside the bean. This CO2 is trapped inside and is gradually released over time. This slow release of gas is called "de-gassing" and typically occurs over the space of two to three weeks after the coffee beans have been roasted.

Grinding the beans increases the total surface area and encourages the coffee to de-gas quicker. So if you want to maintain the freshness of your coffee for longer, buy them in whole bean form and grind only when needed. Then use the ground coffee immediately.

Now, you may ask, what is this "bloom" that is the subject of this blog post?

Well, this gas is released rapidly when the coffee beans come into contact with hot water. You can see this very easily if you're using a conical dripper, such as a V60, and pour a small amount of hot water onto the coffee grounds inside the cone of filter paper. Check out this short video demonstrating the bloom in action...


You can see why using freshly roasted coffee is extremely important. This release of gas when starting to brew your coffee brings out the full flavour and ensures you get a cup bursting with flavour.

Using the Coffee Bloom to Your Advantage

How the bloom differs with the age of the roasted coffee

To determine how the bloom varies with the age of roasted coffee beans, you can perform a comparison test using beans that are one week and one month old. By preparing coffee with each set of beans using the same recipe, you can observe differences in the bloom. This experiment will help you evaluate whether you have been storing your beans correctly, ensuring their freshness and flavour.

Using pre-infusion when brewing espresso

Using a pre-infusion or pre-wet program in espresso machines can significantly enhance the brewing process. This technique involves the initial gentle soaking of the coffee grounds in the portafilter by the machine.

Such soaking allows the coffee particles to settle and evenly absorb water, promoting a more uniform extraction of flavours when full brewing commences. This process also offers a chance to mitigate minor inconsistencies in coffee distribution and tamping.

By initiating this 'bloom,' the likelihood of achieving a consistently high-quality espresso is increased, benefiting both professional baristas and home enthusiasts by delivering a smoother and more balanced shot.

Using the correct water temperature

The relationship between the temperature of the brewing water and the coffee bloom process is key to achieving the right extraction from the coffee grounds.

To understand this, we must consider that the coffee bloom is essentially the release of gas and oils that occurs when hot water first contacts the coffee grounds. For this bloom to be most effective, the water temperature should ideally be between 92 and 96 degrees Celsius.

At these temperatures, the heat acts as a catalyst, speeding up both the blooming and brewing processes. This is because higher temperatures facilitate a quicker dissolution of matters into the water, including the gases and oils trapped within the coffee grounds. When the temperature is within this range, the bloom is typically vigorous, resulting in visible bubbling and foaming. This rapid release of gases is not only a visual indicator of an active bloom but also suggests a proper extraction process.

Conversely, if the water is too cool, below this optimal temperature range, the release of gases and oils is slower and less effective, which can be identified by a lack of aggressive bubbling. This slower process may result in an under-extracted brew, leaving some of the coffee's flavors and oils still locked within the grounds. Therefore, observing the nature of the bloom can provide useful feedback on whether the water temperature used was adequate, with a lively and energetic bloom indicating a suitable temperature for brewing.

Use the right amount of water

To properly bloom coffee, it is recommended to use twice the amount of water as the coffee grounds you are using. For instance, if you are using 20 grams of coffee, then you should add 40 grams of water. Ensure that you pour the water slowly and carefully to maintain the integrity of the coffee bed and promote even saturation. This technique helps prepare the coffee for a more uniform extraction during the brewing process.

How does roast degree affect the bloom?

The way coffee blooms during brewing is significantly influenced by the roast degree of the beans. Lightly roasted coffee beans typically have less oil and gas content. As such, the blooming process, which involves the release of carbon dioxide when hot water contacts the coffee grounds, is less vigorous for lightly roasted beans. The minimal gas content in these beans gets further reduced if the coffee is stored for an extended period, say a month or more, after roasting. Consequently, the bloom becomes less pronounced, giving an indication of both the roast level and the age of the coffee.

In contrast, darkly roasted coffee beans contain more oils and gases. The intense roasting process facilitates further chemical transformations within the beans, leading to increased gas production and the accumulation of oils on the bean surfaces. These oils can partly trap the gases within the beans. As a result, dark roasts often display more robust and longer-lasting blooms. This phenomenon may lead to the false impression that the coffee is fresher than it actually is, based on the bloom alone. The bloom in dark roasted beans is more pronounced, falsely indicating freshness for a more extended period post-roasting.

It is crucial for coffee enthusiasts to understand that while darker roasts might seem fresher due to their bloom, this does not necessarily correlate with actual freshness or optimal flavour. The recommended practice is to use freshly roasted beans, ideally within a week of roasting, to enjoy the best flavour profile possible, regardless of the roast degree.

Thus, the degree of roast has a direct impact on the coffee bloom, and observing the bloom can provide insights into the roast level and relative freshness of the coffee. Light roasts typically exhibit less bloom, especially as they age, while dark roasts show a more vigorous bloom that may mislead about their fresher state.

Grind just before brewing

Grinding coffee well in advance of brewing can significantly deteriorate both the bloom and overall flavour quality of the coffee. The concept of pre-grinding—the practice of grinding beans minutes to hours before brewing—can harm the coffee experience in a couple of critical ways.

First, the coffee bloom, which is largely caused by the release of gases that are trapped within the coffee beans during the roasting process, is greatly diminished. Freshly ground coffee retains these gases, but once ground, the rapid release of these gases occurs, leading to a less vibrant bloom when water first hits the coffee during brewing.

Furthermore, pre-grinding increases the coffee’s exposure to oxygen, which accelerates oxidation and degradation of vital flavour compounds in the coffee. This exposure reduces the coffee's freshness and results in a flat and less flavourful cup. Active gases that normally escape slowly when coffee is brewed soon after grinding escape much faster when the coffee is ground well ahead of time.

This hastens the loss of those fresh, delicate flavours that are prominent in a freshly brewed cup. Thus, to maintain optimal bloom and flavour, coffee should ideally be ground just before brewing.

This practice ensures that the maximum amount of gas remains within the coffee grounds to enhance the bloom and, subsequently, preserves the integrity and complexity of the coffee’s flavour during extraction.

Storing the coffee properly

Proper storage of coffee plays a vital role in preserving its quality and enhancing its performance during the brewing process, particularly in facilitating the blooming phase.

Blooming occurs when hot water first contacts the coffee grounds, causing them to release gases and expand, which is crucial for optimal flavour extraction. When coffee is stored correctly at room temperature and protected from light, moisture, and air, it maintains its freshness and ability to bloom effectively.

Storing coffee in conditions that are too warm can hasten the aging process, leading to diminished blooming even if the coffee is still within its recommended use date. This affects the overall brewing as the coffee fails to release all its flavours and aromas.

Conversely, storing coffee in very cold temperatures, such as below freezing, can slow down the aging process and preserve the flavours longer, thus maintaining its blooming capability.

It's important to balance these storage conditions to ensure the coffee remains lively and flavourful for the best brewing experience.

Should espresso be stirred to break up the crema?

When considering whether to stir espresso to break up the crema, it's important to understand the role and nature of crema in an espresso shot.

Crema, the creamy layer of foam that forms on top of a freshly brewed espresso, consists of tiny micro-foam bubbles that encapsulate elements of the espresso’s flavour and aroma. While visually appealing and iconic to the espresso experience, the presence of crema also influences the taste and texture of the drink.

Stirring the espresso disrupts this layer of crema, causing the micro-foam bubbles to burst and thus dissipate more quickly. For those who prioritize the pure flavour of the coffee, breaking up the crema can enhance the tasting experience by providing more immediate access to the espresso itself, free from the slight bitterness and lighter texture that the crema might impart.

This method is especially favoured in taste tests where the essential qualities of the espresso are evaluated without the interference of crema. On the other hand, crema serves not only as a pleasure to the eye but also as a protector of the coffee's quality, shielding it momentarily from oxidation.

For many enthusiasts, the crema is considered an integral part of the espresso experience, offering both a visual marker of a well-prepared espresso and a component of the sensory journey, from its texture to subtle flavour notes. In summary, whether or not to stir the espresso fundamentally depends on personal preference.

Stirring allows the drinker to experience a clearer, possibly more robust flavour of the espresso, unmediated by the crema. Those who value a traditional espresso might prefer to leave the crema intact, enjoying the full range of sensory experiences that it provides.

Thus, the decision to stir should align with the drinker's taste preference and the way they wish to experience their espresso.

Back to blog