Where Do the Crackling Sounds in Coffee Roasting Come From?
Roasters frequently hear crackling sounds when roasting beans. Where do these crackling sounds originate, and why do they occur? Coffee roasting is the process of placing green coffee beans in a heat-resistant vessel and applying heat, which causes a series of physical and chemical reactions both inside and outside the bean. During this process, various flavors, such as acidity, bitterness, and sweetness, are generated, and the coffee's body (mouthfeel) and color are developed, transforming the green beans into dark brown roasted beans. The crackling sounds in coffee roasting are the result of the pyrolysis process occurring during the coffee bean's "First Crack" and "Second Crack." Taking a heat-resistant green bean as an example, the First Crack begins around the 7-minute mark and lasts for approximately two minutes. This sound is low and dull, signifying the onset of pyrolysis, the caramelization of starches, moisture evaporation, and the release of i...