OPTIMIZATION OF PHENOL EXTRACTION FROM GRAPE POMACE USING ECO-FRIENDLY SOLVENTS AND DIFFERENTIATED THERMAL TREATMENTS

Abstract

This study examines the effects of solvent type and temperature on the extraction efficiency of phenolic compounds from grape pomace. Four solvents were tested: 50 % hydroalcoholic solution, 3 % and 5 % citric acid solutions, and pectinase, with extractions conducted at 20 °C, 40 °C, and 60 °C. The results indicate that the hydroalcoholic solvent at 20 °C yielded the highest extraction of total polyphenols, anthocyanins, and catechins. Increasing the temperature caused significant degradation of thermally sensitive phenolics, particularly anthocyanins, which was also evidenced by reduced color intensity of the extracts. The Folin-Ciocalteu index, serving as an indicator of total antioxidant capacity, correlated strongly with total polyphenol content, validating the analytical approach. While citric acid- and pectinase-based solvents showed lower extraction efficiency, they maintained better compound stability at higher temperatures. These findings suggest that hydroalcoholic extraction at low temperatures optimizes phenolic yield from grape pomace by minimizing thermal degradation and preserving antioxidant activity.