Microstructural Evolution of Coffee Beans during Aqueous-based Decaffeination
6 affiliations
- 1ISIS Neutron and Muon Source
- 2STFC
- 3Department of Physics and Astronomy, McMaster University, 1280 Main St. W., Hamilton, Canada, L8S 4M1
- 4The University of Manchester at Harwell, Diamond Light Source
- 5Electrochemical Innovation Lab, Department of Chemical Engineering
- 6University College London
Abstract
Aqueous decaffeination removes caffeine before roasting but may also alter the green-bean microstructure that contributes to subsequent heat and mass transfer. This study used X-ray micro-computed tomography (µ-CT) to quantify time-dependent changes in the three-dimensional pore structure of intact Colombian Arabica coffee beans treated using a laboratory-scale protocol termed the Thame Water Method (TWM). Two beans were imaged in their raw states. One was subsequently imaged after 8 hr of treatment, while the second was imaged after 5 min and 30 min of treatment. Pore number decreased in both treatment windows, falling by approximately 22% after 30 min and 68% after 8 hr. During 30 min short-duration treatment, mean pore diameter and resolved porosity increased, whereas both decreased following prolonged treatment of 8 hr. A numerical model informed by the measured microstructures predicted slower heating for the 30 min microstructure and faster heating for the 8 hr microstructure relative to the raw bean under the same roasting profile. These findings show that aqueous decaffeination can alter the physical starting structure of green coffee beans and suggest that these changes may influence subsequent heating transfer during roasting. The TWM provides a µ-CT-compatible platform and a methodology to investigate structural changes produced by other decaffeination processes. A more complete understanding could ultimately support decisions about how decaffeinated coffee is processed and roasted for optimal cup quality.
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BibTeX
@misc{young2026microstructural,
title = {{Microstructural Evolution of Coffee Beans during Aqueous-based Decaffeination}},
author = {Robert Scott Young and Liam Micheal Farrell and Lorna Sinclair and Danielle Duggins and Sara Nonni and Andrew R. T. Morrison and Francesco Iacoviello},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15009235/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009235/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Microstructural Evolution of Coffee Beans during Aqueous-based Decaffeination
AU - Robert Scott Young
AU - Liam Micheal Farrell
AU - Lorna Sinclair
AU - Danielle Duggins
AU - Sara Nonni
AU - Andrew R. T. Morrison
AU - Francesco Iacoviello
PY - 2026
DA - 2026/09/22
PB - ChemRxiv
DO - 10.26434/chemrxiv.15009235/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009235/v1
AB - Aqueous decaffeination removes caffeine before roasting but may also alter the green-bean microstructure that contributes to subsequent heat and mass transfer. This study used X-ray micro-computed tomography (µ-CT) to quantify time-dependent changes in the three-dimensional pore structure of intact Colombian Arabica coffee beans treated using a laboratory-scale protocol termed the Thame Water Method (TWM). Two beans were imaged in their raw states. One was subsequently imaged after 8 hr of treatment, while the second was imaged after 5 min and 30 min of treatment. Pore number decreased in both treatment windows, falling by approximately 22% after 30 min and 68% after 8 hr. During 30 min short-duration treatment, mean pore diameter and resolved porosity increased, whereas both decreased following prolonged treatment of 8 hr. A numerical model informed by the measured microstructures predicted slower heating for the 30 min microstructure and faster heating for the 8 hr microstructure relative to the raw bean under the same roasting profile. These findings show that aqueous decaffeination can alter the physical starting structure of green coffee beans and suggest that these changes may influence subsequent heating transfer during roasting. The TWM provides a µ-CT-compatible platform and a methodology to investigate structural changes produced by other decaffeination processes. A more complete understanding could ultimately support decisions about how decaffeinated coffee is processed and roasted for optimal cup quality.
ER -