Supramolecular solvents for the valorization of coffee wastewater

Abstract

Supramolecular solvents (SUPRASs) were investigated for the recovery of bioactives from coffee wastewater (CWW), an abundant residue in the wet and semi-wet processing methods of coffee beans. The SUPRASs were made up of hexagonal inverted aggregates of hexanol or decanoic acid and were spontaneously produced in the wastewater through self-assembly processes. The SUPRAS components were authorized food ingredients facilitating future industrial applicability. Under passive extraction (without stirring), caffeine was recovered with a yield of 54 to 65 mg per liter of wastewater. The SUPRAS extracts showed good antioxidant capacity (up to 53% ABTS˙⁺) and were stable for at least 2 months in the range of temperatures investigated (4–24 °C) for the preservation of bioactives. Additionally, the SUPRAS-based extraction of bioactives improved substantially some wastewater quality parameters (e.g. BOD, total suspended solids and conductivity), so this process also helped to purify wastewater before dumping it into surface waters.