Valorisation potential of Cabernet grape pomace for the recovery of polyphenols: Process intensification, optimisation and study of kinetics

The compositional analysis of Cabernet grape pomace showing higher polyphenols, dietary fiber and proteins reveals its potential to be valorised as a possible functional food. For assessment of potential intensification of polyphenols extraction yields, different extraction techniques under various operating conditions were experimented upon and further optimised. Ultrasonication as a standalone technique resulted in lower polyphenols yields. Whereas ultrasonication when combined with conventional shaking extractions and carried out under conditions of 45 degrees C and 40:1 aqueous ethanolic solvent demonstrated higher yields of 2079.33 mg/100 g of dry grape pomace. The predictive yield as per statistical analysis was 2081.66 mg/100 g revealing a close agreement between experimental and theoretical values. Kinetic studies further showed that ultrasonication with subsequent shaking resulted in relatively lower activation energy causing greater and faster diffusion of the polyphenols into the solvent matrix. The outcome of this study reveals that grape pomace has significant antioxidant components like polyphenols; but maximum extraction yields involving lesser energy and time requires the involvement of a shorter ultrasonication in combination with conventional shaking extractions under optimized process control. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.