What allows the coffee bloom to occur during the brewing process?

The coffee bloom occurs primarily due to the release of carbon dioxide from the coffee grounds. When coffee beans are roasted, gases, particularly carbon dioxide, are formed and trapped within the coffee grounds. During the brewing process, when hot water is applied to the grounds, the heat causes these gases to escape rapidly. This release creates bubbles and a rising effect, which is referred to as "blooming." The blooming process is particularly important because it allows for an even extraction of flavors from the coffee grounds when brewing.

The other options do not directly contribute to this phenomenon. For instance, applying cool water does not promote the release of carbon dioxide; instead, hot water is necessary for the bloom to occur. High-pressure brewing techniques may affect the overall extraction of coffee flavors but are not directly related to the blooming process itself. Lastly, adding sugar does not facilitate the release of gases; it simply sweetens the coffee but does not impact the blooming effect of carbon dioxide during brewing.