Optimization of polyphenols extraction from grape residues in water medium

• The extraction of polyphenolics from grape residues was optimized for the production of wood adhesives.
• The study was performed using microwave activation and response surface methodology.
• The microwave assisted extractions gave higher yields as compared to traditional extraction.

The extraction in water of polyphenolics from grape red marc, grape white marc and grape pomace for the production of wood adhesives was optimized using microwave extraction in presence of Na2CO3. The reaction parameters studied were the temperature (60–120 °C), the residence time (5–20 min) and the sodium carbonate concentration (0–2.5%) using response surface methodology based on central composite design. The optimal values of the variables were as the followings: 100 °C, 8 min, without sodium carbonate from grape marcs and 100 °C, 8 min, 2.5% w/w of sodium carbonate for pomace. The microwave assisted extractions gave significantly higher yields as compared to traditional extraction and could be recommended as an alternative method for extraction of phenolic compounds from grape residues in water medium.