Orthogonal test design for optimisation of extraction of trans-resveratrol from Pinot Noir-grape pomace

Yield of trans-resveratrol from Pinot Noir-grape pomace obtained by microwave-assisted extraction (MAE) through an orthogonal experiment (16 (4(4))) was investigated to get the best extraction conditions. In this method, the highest yield was obtained when the extraction solvent used ethanol; the ratio of raw material to solvent, the extraction time, the extraction temperature and microwave irradiation power were 1:20 (g mL(-1)), 30 min, 55°C and 1.0 kW, respectively. The average yield of trans-resveratrol was 90.87%, and the recovery was in the range of 85.49-89.04% with relative standard deviation lower than 1.39%. Then, the extract of MAE was separated by NKA-9 macroporous resin and re-crystallisation. Finally, the purity of trans-resveratrol was 97.47%.