What causes sweating in coffee during the roasting process?

Sweating in coffee during the roasting process primarily occurs when the roast extends past the second crack or when green beans have been dried at excessively high temperatures. When coffee beans roast past the second crack, they enter a phase where volatile compounds and moisture are expelled more significantly from the beans, causing the surface to retain moisture and create sweat.

Additionally, if green beans are dried at too high a temperature, it can lead to uneven moisture distribution within the beans, which can aggravate the sweating phenomenon during roasting. This is significant because proper temperature management throughout both the drying and roasting stages directly impacts the final flavor and quality of the coffee.

Understanding this mechanism allows roasters to fine-tune their processes to avoid unwanted moisture and ensure optimal flavor extraction, maintaining the integrity of the coffee's characteristics. This knowledge also underscores the importance of monitoring both temperature and humidity levels during roasting to achieve the desired outcome.