During the roasting of coffee, thermally driven chemical reactions lead to the formation of gases, of which a large fraction is carbon dioxide (CO2). Part of these gases is released during roasting while part is retained inside the porous structure of the roasted beans and is steadily released during storage or more abruptly during grinding and extraction.

The release of CO2 during the various phases from roasting to consumption is linked to many important properties and characteristics of coffee. It is an indicator for freshness, plays an important role in shelf life and in packaging, impacts the extraction process, is involved in crema formation, and may affect the sensory profile in the cup.

Indeed, and in view of the multiple roles it plays, CO2 is a much underappreciated and little examined molecule in coffee. Here, we introduce an accurate, quantitative, and time-resolved method to measure the release kinetics of gases from whole beans and ground coffee using a gravimetric approach. Samples were placed in a container with a fitted capillary to allow gases to escape.

 The time-resolved release of gases was measured via the weight loss of the container filled with coffee. Long-term stability was achieved using a customized design of a semimicro balance, including periodic and automatic zero value measurements and calibration procedures. The novel gravimetric methodology was applied to a range of coffee samples: (i) whole Arabica beans and (ii) ground Arabica and Robusta, roasted to different roast degrees and at different speeds (roast air temperatures). Modeling the degassing rates allowed structural and mechanistic interpretation of the degassing process.

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첨부 사진은 SCA 슬라이드 중 몇 가지 추렸습니다. 논문 기반 슬라이드 자료이기도 하고, 논문을 바탕으로 씌여진 SCA 신선도 관련 핸드북 자료 요약본입니다. 

시간에 따라 휘발되는 Gas 들의 누적량(대다수 이산화탄소)을 그래프로 나타낸 자료고 x,y 축선만 봐도 무슨 말인지 이해하긴 어렵지 않습니다. 로스팅에 레벨에 따른 디개싱 차이, 혹은 이와 관련한 상미 기간에 대한 부분을 유추할 수 있고 로스팅 레벨에 따라서도 로스팅 속도에 따른 디개싱 상태를 알아볼 수 있습니다. 

참고하시길.