Acid Hydrothermal Amendment of Grape Wine Pomace: Enhancement of Phenol and Carbohydrate Co-Solubilization

Abstract

Byproducts from the winery industry contain many bioactive compounds that are considered high-value-added compounds. White grape pomace (GP) is rich in carbohydrates; consequently, it can be used as a raw material for subsequent bioprocesses. In the present study, low-temperature hydrothermal treatments were carried out using different operational conditions regarding temperature (65–95 °C), time (120–240 min), and sulfuric acid addition at various concentrations (5–15% v/v). The results showed that by using a temperature of 65 °C, a period of 120 min, and 15% (v/v) of H2SO4, it was possible to obtain a liquid phase rich in phenols and carbohydrates, with total phenol compounds corresponding to 2113 ± 140 mg of gallic acid/kg GP and composed mainly of 3-hydroxytyrosol (1330 ± 22 mg/kg GP). In parallel, carbohydrate solubilization reached 245 g glucose/kg GP. These results demonstrate the promising potential of hydrothermally treated grape pomace as raw material for biorefinery processes.

Keywords

• hydrothermal treatment
• grape pomace
• phenolic compounds
• 3-hydroxytyrosol
• carbohydrates