Multi-frequency multimode modulated technology as a clean, fast, and sustainable process to recover antioxidants from a coffee by-product

Coffee chaff is a major coffee roasting by-product that could be valued as a source of antioxidants. In the present work, we compared classic, but optimized, solid-liquid extraction conditions with a new concept, namely, the Multi-frequency Multimode Modulated (MMM) vibration technique. The extracts obtained by both methods were analysed and compared in relation to several parameters, namely, phenolics profile (by HPLC/DAD), 5-caffeoylquinic acid content, total phenolics content, and Ferric Reducing Antioxidant Power. Compared to an optimized solid-liquid extraction (using a hydroethanolic solvent (1:1) at 40 degrees C for 60 min), the acoustic probe allowed a higher recovery of antioxidants in only 10 min and using only water as extraction solvent. Moreover, the effects that arise from the acoustic cavitation in the medium allowed the suppression of the sample preparation step (grinding). These results show that this type of technology can be of high interest to recover antioxidants from natural matrices, in a green, fast and very efficient way. (C) 2017 Elsevier Ltd. All rights reserved.