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 degree sC) in contact with air was also determined. All the assayed phenolic compo unds were stable under the extraction conditions with the exception of cate chin and epicatechin (recoveries: 87.4% for catechin and 86.0% for epicatec hin at 150 degreesC and 94.1% for epicatechin at 100 degreesC). Phenolic co mpounds kept at the boiling point of methanol (65 degreesC) showed lower re coveries: gentisic acid (85.5%), syringic aldehyde (92.8%), catechin (63.7% ) and epicatechin (63.4%). Extraction with superheated solvents was also ap plied to the extraction of phenolic compounds from solid wastes of the wine making process. (C) 2001 Elsevier Science B.V. All rights reserved.