Effect of experimental parameters in the pressurized solvent extraction of polyphenolic compounds from white grape marc

• A PSE method has been optimized to extract polyphenols from white grape marc.
• The chemometrics tools used were screening and response surface methodology.
• Gallic acid, catechin and epicatechin were the main polyphenolic compounds present.
• Raw PSE extracts can be exploited by their high antioxidant activity.

A method based on pressurized solvent extraction (PSE) to determine main polyphenolic compounds in the grape marc obtained as a byproduct of the white winemaking process has been developed. As response variables in the optimisation process include main individual polyphenols, as well as spectrophotometric indexes. The optimised PSE procedure implies the use of 1 g of sample, without preliminary clean-up step, sea sand as dispersant, temperature of 105 °C, methanol (63%) in water as solvent, and 5 min of extraction time (2 static cycles). The performance of the proposed method has been assessed in terms of recovery (91–105%), linearity (R2 > 0.995) and precision. The applicability of the method was demonstrated by the analysis of bagasse samples collected from 12 wineries located in Galicia (NW Spain). Data of the in vitro antioxidant activities of the PSE extracts are also discussed.