Caffeine removal and compositions losses from whole Robusta coffee beans during conventional and ultrasound-assisted aqueous decaffeination

Abstract

Whole Robusta coffee beans were decaffeinated using conventional aqueous extraction (CAE) and ultrasound-assisted aqueous extraction (UAAE). Changing of extraction water at time intervals to enhance caffeine removal efficiency is proposed as novel decaffeination technique. Kinetic modelling of caffeine content evolutions during CAE and UAAE, with and without water changing, was performed to confirm benefit of newly proposed technique. Losses of soluble carbohydrates, phenolics, sugars, flavonoids and organic acids from decaffeinated beans were investigated. Recycling of extraction water as way to recover lost compositions was tested. Water changing enhanced caffeine removal efficiency, especially in case of UAAE; caffeine could be removed by 98%. Kinetic model well described caffeine content evolutions (R² = 0.99). This strategy nevertheless led to significant losses (p < 0.05) of bean compositions when compared to CAE. UAAE with water recycling could not help recover bean compositions, but drying and soaking beans in spent extraction water from second round of decaffeination significantly increased (p < 0.05) total soluble carbohydrates and phenolics contents.