Effects of temperature and pressure on hydrothermal extraction kinetics of green coffee beans

• Published in: The Journal of supercritical fluids Vol. 213; p. 106350
• Main Authors: Sato, Takafumi, Kudo, Takeru, Takamatsu, Masato, Honma, Tetsuo, Itoh, Naotsugu
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-11-2024
• Subjects: Antioxidants; Caffeoylquinic acids; Coffee beans; Extraction curve; Hydrothermal extraction; Hydrothermal extraction; Antioxidants; Caffeoylquinic acids; Coffee beans; Extraction curve
• ISSN: 0896-8446
• DOI: 10.1016/j.supflu.2024.106350

Hydrothermal extraction of green coffee beans was examined by using a semi-batch type apparatus and an optical cell for extracting beneficial compounds. Extraction curves were evaluated across varying temperatures (373–523 K) and pressures (0.6–2.1 MPa). At 473 K, increasing pressure enhanced the extraction of caffeoylquinic acids (CQAs), total phenolic content (TPC), antioxidant capacity (AOC), and caffeine. At 2.1 MPa, TPC remained constant with temperature, while AOC, CQAs, and caffeine initially increased then decreased at higher temperatures. Direct observations confirmed high temperature promoted extraction. An extraction model was proposed to account for decomposition of components at high temperatures, effectively reproducing experimental curves. This model estimated equilibrium values and rate constants representing initial extraction rate. The obtained results indicate that adjusting temperature, extraction time, and pressure can control extract composition during hydrothermal extraction of green coffee beans.
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•Hydrothermal extraction of green coffee beans was examined.•Swelling and dissolution of beans were observed using an optical cell.•Antioxidants, total phenolic contents, caffeoylquinic acids and caffeine were evaluated.•Some extraction curves changed complicatedly with temperature.•The proposed model expressed the dependence of the extraction curve on temperature.