Chemical characterization of Grechetto grape pomace for potential valorization in a biorefinery perspective

The Organisation Internationale de la Vigne et du Vin (OIV) assessed vineyard among the main crops worldwide and the resulting waste represent a critical issue. Winery waste and their content of natural active principles have been extensively explored for changing them into new resources with high added value. The recovery of bioactive phenols and polysaccharides from pomace offers promising opportunities for producing novel ingredients across different sectors, enhancing winery economic sustainability and reducing environmental impact. In this scenario, studies concerning white grape cv Grechetto, widely cultivated in Italy, are very limited. The present work studied the possibility of exploiting white Grechetto whole pomace, skins and seeds, in a biorefinery perspective for a large-scale green extraction process to implement in the winery. Grechetto dried pomace were investigated by Fourier Transform Infrared Spectroscopy– Attenuated Total Reflectance (FTIR-ATR) to obtain a qualitative fingerprint. Polyphenols were characterized by High Performance Liquid Chromatography coupled with Diode Array and Mass Detectors (HPLC-DAD-MS) and Folin-Ciocalteu assay; polysaccharides by Dynamic Light Scattering (DLS), chemical hydrolysis and Proton Nuclear Magnetic Resonance (1HNMR) spectroscopy. Total phenols were 51 ± 1, 25.36 ± 0.08 and 85 ± 2 mg/g GAE on whole dried pomace, skin and seed respectively, with similar trend obtained by HPLC-DAD-MS. Crude polysaccharides, studied for the first time in white Grechetto, were 12%, 13% and 8% on dried whole pomace, skins and seeds. They were present in relatively high quantities, with glucuronic acid, acetyl and methyl groups similar to pectin, suggesting their potential use as a gelling agent.