The role of heating step in microwave-assisted extraction of polyphenols from spent coffee grounds

• Published in: European management journal 2019-03, Vol.114 (2), p.227-234
• Main Authors: Pettinato, Margherita, Casazza, Alessandro Alberto, Perego, Patrizia
• Format: Article
• Language: English
• Subjects: ABTS[rad]+ assay; Antioxidants; By-product valorization; Coffee; Extraction; Extraction processes; Folin-Ciocalteu’s assay; Heating; Investigations; Kinetics; Microwaves; Peleg’s model; Polyphenols; Power
• ISSN: 0960-3085; 0263-2373; 1744-3571; 1873-5681
• DOI: 10.1016/j.fbp.2019.01.006

•MAE extracts from SCG are a rich natural source of polyphenols.•Heating time affects the extract quality and composition.•Peleg’s model allowed to highlight the dependence from the process variables.•High yields can be obtained operating at 423K, 60min and 10min of heating. Microwave-assisted extraction is currently one of the most studied techniques for biomolecule recovery from natural sources, due to its favorable features for the treatment of thermo-sensitive compounds. In this work, the kinetic of antioxidant extraction from spent coffee grounds was investigated, focusing the attention on the effects of initial thermal ramp on the total polyphenol concentration, total solids and antiradical power of the final product. The hydro-alcoholic extracts demonstrated to be very rich of antioxidants with high antiradical power (from 0.45 to 0.88μTroloxequivalent/g dried spent coffee grounds), and their quality was significantly affected by the investigated variables. Peleg’s model, was successfully used to describe extraction kinetics, whose investigation revealed that 10min of heating time at 423K provided the highest concentration of polyphenols, and resulted as a good compromise to perform a fast extraction with high extraction yields (43mgCaffeic Acid Equivalent/g dried spent coffee grounds after 60min of extraction).