Stability of phenolic compounds during extraction with superheated solvents

The stability of nine phenolic compounds in the extraction with superheated methanol at different temperatures (40, 50, 100 and 150 degreesC) has been tested. The evolution of the same compounds in boiling methanol (65 degreesC) in contact with air was also determined. All the assayed phenolic compounds were stable under the extraction conditions with the exception of catechin and epicatechin (recoveries: 87.4% for catechin and 86.0% for epicatechin at 150 degreesC and 94.1% for epicatechin at 100 degreesC). Phenolic compounds kept at the boiling point of methanol (65 degreesC) showed lower recoveries: gentisic acid (85.5%), syringic aldehyde (92.8%), catechin (63.7%) and epicatechin (63.4%). Extraction with superheated solvents was also applied to the extraction of phenolic compounds from solid wastes of the winemaking process. (C) 2001 Elsevier Science B.V. All rights reserved.