Effect of instant controlled pressure drop (DIC) pre-treatment on conventional solvent extraction of phenolic compounds from grape stalk powder

In this paper, we quantified the impact of an instant controlled pressure drop (DIC) pre-treatment prior to conventional solvent processes on the yields of six phenolic compounds extracted from grape stalk powder of the Monastrell variety (Vitis vinifera L.). Results indicate that DIC treatment had a positive and significant effect in the concentration of these compounds. Mainly, the DIC treatment increased the availability of gallic acid, quercetin, ellagic acid and resveratrol in 50% (v/v) aqueous ethanol, ethyl acetate or propanol extracts. It had a much greater effect than the solvent used in the extraction process. More polar solvents (ethanol and propanol) were efficient to extract phenolic acids (gallic, caffeic and ellagic acids) and stilbenes (resveratrol), while a moderately polar solvent (ethyl acetate) did for flavonoids [(+)-catechin and quercetin]. The classic process of extraction could be intensified varying different DIC operative parameters such as steam pressure, water content of plant material and duration,of treatment. (C) 2015 Elsevier B.V. All rights reserved.