Effect of solvent composition and its interaction with ultrasonic energy on the ultrasound-assisted extraction of phenolic compounds from Mango peels (Mangifera indica L.)

Ultrasound has been used to intensify the extraction of phenolic compounds from many agro-food products. However, there is still a lack of understanding on how the ultrasonic energy is influenced by blends of different solvents and how this impacts the extraction process. This work studied the effect of ethanol, acetone and hexane blends on the ultrasonic power density (UPD) generated during the extraction of phenolic compounds from Mango peel, using an ultrasonic-assisted extraction (UAE) and a conventional solvent extraction (CSE). A simplex centroid mixture design and a special cubic regression model were used to evaluate the total phenolic compounds (TPC), antioxidant activity (AA) and ultrasonic intensity (UI) as a function of the solvents proportions. The greatest TPC was obtained with the ethanol-acetone blend (60-40%) for CSE (205.08 mg GAE/100 g DM) and UAE (1493.01 mg GAE/100 g DM). Likewise, an increase (avg. 630%) was observed in TPC when the ultrasound was applied for all solvents and their blends. The TPC showed a good correlation (r=0.81) with the UPD, with higher UPD resulting in larger amounts of TPC extracted. Nevertheless, for the ethanol-acetone blend there was a decrease of 14.2% of the AA for the UAE, which could be due to the sonochemical reactions taking place at the high UPD achieved for that blend. The results of this work indicate that the solvent composition and use of ultrasound should be carefully selected to achieve the desired extraction objectives. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.