Novel Zero Headspace Solid-Liquid Extraction for the Recovery of Polyphenolic Fractions from Grape Pomace

Abstract

Grape pomace (GP) is a good source of high-value compounds as up to 60% of grape polyphenols remain in it after wine-making. To overcome traditional membrane technologies’ d rawbacks, such as fouling, a novel Zero Head Space extraction (ZHE) procedure was developed. The reaction vessel comprised a filtration device with a nitrocellulose membrane. The separation was performed at 50 lb/in2 and 23◦ C, with no headspace during the process. Water and methanol (both acidifie d) were evaluated as solvents during two extraction stages for the recovery and fractionation of polyphenols. Aqueous extract (AE) was mainly constituted by monomeric polyphenols while Methanol extract (ME) presented less soluble compounds, as well as a higher concentration of total anthocyanin content than AE. Additional methanolic (CE) and acetone (CAE) extractions of residual GP showed CE presented a similar profile to ME (at a lower concentration), indicating ZHE efficiency at extracting polyphenols in GP. CAE presented a non-resolved hump, characteristic of high proanthocyanidins’ polydispersity. ZHE rendered a monomeric fraction in ME (mean Degree of Polymerization, mDP of 1.38). Residual GP (cake) extractions demonstrated oligomeric polyphenol retention; mDP up to 3.05 when acetone was used. Fractionation of GP polyphenols was successfully established using a Zero Head space extractor.