A biorefinery approach towards valorization of spent coffee ground: Extraction of the oil by supercritical carbon dioxide and utilizing the defatted spent in formulating functional cookies

Abstract

The present work was aimed at the valorization of roasted spent coffee grounds (SCG), a major valuable and functional by-product of the coffee processing industry by supercritical fluid extraction (SCFE) of the oil therefrom using carbon dioxide, and utilizing the spent residue for the development of functional cookies. The process parameters of SCFE were optimized and compared with conventional Soxhlet extraction using n-hexane, following which the effect of different entrainers was evaluated under optimized conditions of SCFE (300 bar/50 °C/90 min) to obtain the maximum yield of spent coffee oil. SCFE with methanol and ethanol as entrainers at 30% (v/w) of SCG showed marginally better yields of 17.65% w/w and 16.02% w/w than 15.89% w/w obtained by hexane extraction for 16 h. The residue obtained after extraction (SCGR) was analyzed for total polyphenol content (TPC) and antioxidant activities. The SCGR was used for the preparation of cookies and compared with SCG for their textural, bioactivity, prebiotic activity, and sensory analysis. SCGR at 7% (w/w) showed the highest overall acceptability (7.3) in terms of texture and taste. Thus, the biorefinery approach presented in this work would enable the use of coffee oil as well as the defatted SCGR as a novel ingredient enriched with prebiotic activity in future food formulations.