Work

Recovering bioactive compounds and antioxidant capacity of medium roasted spent coffee grounds through varied hydrothermal brewing cycles

Year: 2025

Type: article

Abstract: Spent coffee grounds (SCGs) are the residual product from brewing coffee and contain valuable bioactive compounds. This study investigated the bioactive compounds and antioxidant capacity of medium roasted Arabica and Robusta SCGs subjected to three different cycles of hydrothermal processing, comparing them to unbrewed coffee grounds. SEM imaging showed that brewing increased SCG porosity, allowing more moisture retention and enhanced extraction of further compounds. With further processing SCGs became darker and less pigmented. Fourier-transform infrared (FTIR) spectra confirmed key compounds such as caffeine and chlorogenic acids. Ethanol extraction yielded higher total phenolic content (TPC), while water extraction resulted in greater total flavonoid content (TFC); however, both decreased with additional hydrothermal brewing cycles. Caffeine and chlorogenic acid were more abundant in ethanol extracts, whereas water extracts exhibited stronger antioxidant activity (measured by ABTS and FRAP), particularly in Robusta SCGs. Additional brewing cycles of SCGs were associated with reduced phenolic and flavonoid content, caffeine and antioxidant activity. Significant correlations between TPC, TFC, caffeine, and antioxidant measures underscore the potential for the sustainable reuse of SCGs as a bioactive resource. Overall, optimizing hydrothermal processing conditions enhanced the extraction and utilization of bioactive compounds from SCGs, contributing to the development of value-added products that promote health and sustainability.

Source: Journal of Agriculture and Food Research

DOI: 10.1016/j.jafr.2025.101789