Coffee brewing sonoreactor for reducing the time of cold brew from several hours to minutes while maintaining sensory attributes

Shih-Hao Chiu; Nikunj Naliyadhara; Martin P Bucknall; Donald S Thomas; Heather E Smyth; Jaqueline M Nadolny; Kourosh Kalantar-Zadeh; Francisco J Trujillo

doi:10.1016/j.ultsonch.2024.106885

Coffee brewing sonoreactor for reducing the time of cold brew from several hours to minutes while maintaining sensory attributes

Ultrason Sonochem. 2024 Apr 23:106:106885. doi: 10.1016/j.ultsonch.2024.106885. Online ahead of print.

Authors

Shih-Hao Chiu¹, Nikunj Naliyadhara², Martin P Bucknall³, Donald S Thomas⁴, Heather E Smyth⁵, Jaqueline M Nadolny⁵, Kourosh Kalantar-Zadeh⁶, Francisco J Trujillo⁷

Affiliations

¹ School of Chemical Engineering, University of New South Wales, Sydney 2052, NSW, Australia; School of Chemical and Biomolecular Engineering, The University of Sydney, Sydney 2008, NSW, Australia.
² School of Chemical Engineering, University of New South Wales, Sydney 2052, NSW, Australia.
³ Bioanalytical Mass Spectrometry Facility, Mark Wainwright Analytical Centre, University of New South Wales, Sydney 2052, NSW, Australia.
⁴ NMR Facility, Mark Wainwright Analytical Centre, University of New South Wales, Sydney 2052, NSW, Australia.
⁵ Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, Brisbane 4072, Queensland, Australia.
⁶ School of Chemical and Biomolecular Engineering, The University of Sydney, Sydney 2008, NSW, Australia. Electronic address: kourosh.kalantarzadeh@sydney.edu.au.
⁷ School of Chemical Engineering, University of New South Wales, Sydney 2052, NSW, Australia. Electronic address: francisco.trujillo@unsw.edu.au.

Abstract

This research designed and developed an ultrasonic reactor for a fast and on demand production of cold brew coffee, remarkably reducing the brewing time from 24 h to less than 3 min. The technology was engineered by utilizing resonance to induce ultrasonic waves around the walls of the brewing basket of an espresso machine. The sound transmission system comprised a transducer, a horn and a brewing basket. This arrangement transformed the coffee basket into an effective sonoreactor that injected sound waves at multiple points through its walls, thereby generating multiple regions for acoustic cavitation within the reactor. Furthermore, acoustic streaming induced greater mixing and enhanced mass transfer during brewing. The design was accomplished by modeling the transmission of sound, and acoustic cavitation. Brew characterization and chemical composition analysis was performed, considering factors such as pH, acidity, color, and the composition of caffeine, fatty acids, and volatiles. The efficiency of the extraction increased by decreasing the basket loading percentage (BLP). For instance, sonicating at 100 W doubled the extraction yield and caffeine concentration, from 15.05 % to 33.44 % at BLP = 33 %, and from 0.91 mg/mL to 1.84 mg/mL at BLP = 67 %, respectively. The total fatty acids increased from 1.16 mg/mL to 9.20 mg/mL, representing an eightfold increase, at BLP = 33 %. Finally, a sensory analysis was conducted to evaluate appearance, aroma, texture, flavor, and aftertaste, which demonstrated that coffee brewed for 1 and 3 min in the sonoreactor exhibited almost undistinguishable properties compared to a standard 24 h brewing without ultrasound.

Keywords: Cavitation modelling; Coffee brewing; Food processing; Sonoreactor; Ultrasonication.