Ultrasound enables espresso-strength coffee brewing in 2–3 minutes at low temperature with lower energy consumption

Abstract

This study demonstrates that espresso-strength coffee can be brewed at low temperature in 2–3 min using a patented ultrasonic brewing sonoreactor that couples high-intensity ultrasound directly into a coffee basket during water percolation through a freely packed coffee bed. A novel horn design was developed to excite dominant resonance modes in the coffee basket, creating a resonant ultrasonic reactor with multiple cavitation zones and a more stable ultrasonic generator operation. By tuning grind size, brew ratio, ultrasound power, and extraction time, ultrasound-assisted extraction achieved total dissolved solids (TDS) and extraction yields (EY) within the range associated with traditional espresso, reaching the Speciality Coffee Association (SCA)-defined ideal EY region (18-22 %) at the finest grind tested. Under identical conditions without ultrasound, espresso-strength extraction could not be achieved at low temperature. No statistically significant differences were detected in key physicochemical markers (colour, pH, caffeine, and chlorogenic acid concentrations) between methods (p > 0.05), and headspace volatile profiling showed no significant overall differences in aroma composition under the tested conditions. Consumer sensory testing indicated no significant preference between ultrasound-brewed and conventional espresso across key hedonic attributes (p > 0.05) under the tested conditions, while ultrasound-brewed filter coffee was significantly preferred over conventional pour-over (p < 0.05). Moreover, energy measurements showed that, at matched beverage strength (TDS), the ultrasonic system consumed only 24.3% of the energy required by a conventional espresso machine (≈75% reduction). Overall, ultrasound-assisted percolation enables rapid, low-temperature production of both espresso and filter-style coffees with acceptable hedonic performance, offering a versatile and energy-efficient alternative to traditional brewing technologies.