June 14, 2020 Journal article Open Access

Improving the recovery of phenolic compounds from spent coffee grounds by using hydrothermal delignification coupled with ultrasound assisted extraction.

P. J. Arauzo; M. Lucian; L. Du; M. P. Olszewski; L. Fiori; A. Kruse

This study focuses on the maximization of the phenolic compounds of spent coffee grounds, by coupling hydrothermal delignification with ultrasonic assisted extraction. Temperatures of 200°C, 230 °C and 260 °C were applied for hydrothermal treatment for 1h and 3h. Produced hydrochars contain high values of fuel ratio (0.35 - 0.69) compared to raw feedstock (0.20). The increment of the reaction severity decreases the energy yield from 95.23 % to 82.99 %.   After the hydrothermal treatment, the total phenolic content (TPC of the process water), determined relatively to a gallic acid standard (GAE), was found to be in a similar range for all process conditions (9.52 – 8.07 mg GAE / mg of dry sample). Using methanol as a solvent into produced dry hydrochars during ultrasonic assisted extraction reveals the highest values of TPC (20.33 – 11.66 mg GAE/ mg of dry sample).This study focuses on the maximization of the phenolic compounds of spent coffee grounds, by coupling hydrothermal delignification with ultrasonic assisted extraction. Temperatures of 200°C, 230 °C and 260 °C were applied for hydrothermal treatment for 1h and 3h. Produced hydrochars contain high values of fuel ratio (0.35 - 0.69) compared to raw feedstock (0.20). The increment of the reaction severity decreases the energy yield from 95.23 % to 82.99 %.   After the hydrothermal treatment, the total phenolic content (TPC of the process water), determined relatively to a gallic acid standard (GAE), was found to be in a similar range for all process conditions (9.52 – 8.07 mg GAE / mg of dry sample). Using methanol as a solvent into produced dry hydrochars during ultrasonic assisted extraction reveals the highest values of TPC (20.33 – 11.66 mg GAE/ mg of dry sample).