Remediation of wine with elevated concentrations of 3-alkyl-2-methoxypyrazines using cork and synthetic closures

Author: Gary J. Pickering ^{1, 2*}, Amy J. Blake ¹, George J. Soleas ^{2, 4} and Debra L. Inglis ^{1, 2, 3}

Received 2 September 2009, accepted 2 April 2010.

Abstract

3-alkyl-2-methoxypyrazines (MPs) are potent, odor-active constituents of wine that can contribute atypical and undesired green and vegetative flavours in most wine styles. 3-isobutyl- (IBMP), 3-sec-butyl- (SBMP) and 3-isopropyl- (IPMP) 2-methoxypyrazines, identified in wine, are grape- and insect-derived and resilient to removal using traditional wine-making interventions. A preliminary study was conducted to investigate the relative capacity of commonly used wine closures to mediate MP content in wine. A Chardonnay wine enriched with 40 ngL^-1 each of IBMP, SBMP and IPMP was soaked for 140 hrs with either natural corks, agglomerate corks, moulded synthetic closures or extruded synthetic closures at 2 levels of closure addition (5 and 10 units L^-1). All closures significantly reduced MP concentrations in the wine, with the greatest efficacy observed with synthetic closures (70% - 89% reduction). SBMP was most affected by closure treatments. These findings show, for the first time, that both natural and synthetic cork have significant binding affinity for this important class of wine impact odorants. The use of synthetic cork for potential remediation of MPs in wine both pre- and post-bottling warrants further investigation.

Key words: Methoxypyrazines, wine closures, corks, sorption, greenness, ladybug taint, Harmonia axyridis, flavour scalping, flavour scavenging.