Physicochemical, functional properties and antioxidant activity of protein extract from spent coffee grounds using ultrasonic-assisted extraction

Abstract

Spent coffee grounds, the residue from coffee brewing, are still underutilized even though they contain several useful organic compounds including proteins. To valorize the spent coffee grounds, the spent coffee ground protein was investigated using ultrasonic-assisted extraction as a pretreatment to conventional extraction. The pretreatments involved different ultrasound amplitudes (40%, 60% and 80%) and extraction times (10, 20 and 30 min) and their effects on the physicochemical and functional properties including antioxidant activity of protein extract. It was found that the protein content extracted was increased approximately 2 times, compared to the initial spent coffee grounds. Furthermore, the ultrasonic-assisted extraction affected the physicochemical properties, functional properties and antioxidant activity of the protein extract. The 80% amplitude for 10 min extraction time improved the foaming capacity, foaming stability, emulsifying activity index and the emulsifying stability index of protein extract. The pretreatment at 20 min extraction time provided the highest antioxidant activity (933.92-976.03 mM Trolox eq/g protein extract) and the highest total phenolic content (267.66-304.81 mg GAE/g protein extract). Nonetheless, protein extract using ultrasonic-assisted extraction resulted in higher total phenolic content and antioxidant activity without changes in the protein structure as confirmed by changes in FT-IR spectra and SDS-PAGE profiles. Thus, the spent coffee ground protein can be an interesting and alternative plant protein with functional properties for food application. Moreover, this work showed the feasibility to reduce waste and the food waste valorization.

Keywords

• spent coffee grounds
• protein extract
• ultrasonic-assisted extraction
• antioxidant activity
• functional properties