Spent Coffee Grounds—A Coffee By-Product Abundant in Bioactive Compounds with Antioxidant Properties

Abstract

The present study concentrated on the quality assessment of spent coffee grounds (SCG) blends collected after the brewing process in local commercial cafeterias. To obtain SCG extract and oil, the ultrasound-assisted extraction with 60% hydroethanolic mixture and the conventional solid–liquid extraction with hexane were carried out, respectively. The quality of the SCG blend was assessed by performance of the ensuing analysis: total polyphenols content (TPC), antioxidant activity by using ABTS and FRAP methods, browning index (BI), caffeine and chlorogenic acids contents by using high-performance liquid chromatography as well as oxidative induction time (OIT) by using the pressure differential scanning calorimetry and fatty acids profile by using the gas chromatography. The SCG extract was characterized by a high TPC (33.79 mg GAE/g SCG), BI (0.2), caffeine (5.25 mg/g SCG), and chlorogenic acids (7.52 mg/g SCG) contents. In addition, ABTS and FRAP methods revealed the high antioxidant activity of SCG extract. The OIT of SCG oil reached 43.8 min. The SCG oil mainly contained palmitic acid (37.18%) and linoleic acid (39.69%). Overall, SCG can be regarded as a coffee by-product abundant in various chemical compounds with biological and antioxidant activity, but it is necessary to examine the opportunity for the implementation of SCG in particular forms as a new constituent of functional foodstuffs.

Keywords

• fatty acids profile
• oxidative stability
• polyphenols
• caffeine
• chlorogenic acids
• browning index