Brewing Coffee in Ethanol Instead of Water: A Multi-Technique Pilot Study

Water extracts chlorogenic acids, which contribute to the sourness and bitterness of coffee, together with caffeine. We examined whether a less polar solvent changes that balance. Coarse-ground coffee was brewed for 20 minutes at 75 degrees Celsius in deionized water or 95 percent denatured ethanol and the extracts followed by UV-Vis and infrared spectroscopy; spent grounds from earlier brews were examined by electron and optical microscopy. The caffeine-region band near 275 nm grew about three times faster in water, while the chlorogenic acid region near 320 nm was suppressed proportionally more in ethanol, raising the ratio of the two bands from about 1.2 to 1.5 to 1.7 within a large reading uncertainty, and only the ethanol extracts showed a scattering baseline. Infrared spectra of the undiluted extracts were dominated by the solvents, identified isopropanol as the ethanol’s denaturant and showed no coffee band above the detection limit, and ethanol-brewed grounds more often showed exposed cell walls. These pilot data point to slower, partially selective extraction in ethanol, a direction relevant to lower-acid coffee concentrates, although acidity and caffeine were not measured directly. We also report the measurement problems the data revealed.