Ultrasound-assisted green technology for decaffeination of Gayo Arabica coffee: Process parameter optimization and kinetic modelling

Caffeine reduction inCoffea arabicahas become increasingly important due to growing health concerns related to excessive caffeine intake.This study investigates ultrasound-assisted extraction (UAE) as agreen, solvent-freemethod for the selective decaffeination of Gayo Arabica coffee, using water as the extraction medium. The effects of extraction time (2-12 min), feed-to-solvent (F/S) ratio (0.100-0.150 g/mL), and temperature (40-70 °C) were evaluated. Kinetic modelingwas performed using six models: first-order, second-order, hyperbolic, power law, Elovich, and Weibull. The extraction exhibitedbiphasic behavior, with an initialfast-release phase (2-10 min)followed by aslower diffusion-controlled phase (10-12 min). Among the models tested, thepower law modelprovided the best fit, withR² values up to 0.9881andRMSE as low as 0.0017, demonstrating strong predictive accuracy. Optimal conditionswere achieved at60 °C, 10 min, and an F/S ratio of 0.125 g/mL, yielding66-68 % caffeine recovery. Under these conditions, the power law constants ranged fromB = 0.6247-0.7152andn = 0.1456-0.1891, indicating enhanced mass transfer due to ultrasonic cavitation.Statistical validationvia ANOVA (R2 = 0.9968) and residual analysis confirmed the model's robustness. Compared to conventional methods,UAEshowed significant improvements inenergy efficiency, extraction speed, and preservation of bioactive and sensory properties. This research advancessustainable decaffeination technologiesand offers ascalable kinetic frameworkfor other plant-based bioactive extractions.