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Novel GC-MS strategies for the accurate and sensitive speciation of SO2 in wine

AutorOntañón, Ignacio; Carrascón, Vanesa; Bueno, Mónica ; Ferreira, Vicente
Fecha de publicaciónnov-2016
CitaciónXVI Reunión Científica de la Sociedad Española de Cromatografía y Técnicas Afines (2016)
XVI Scientific Meeting of the Spanish Society of Chromatography and Related Techniques (2016)
ResumenSulfur dioxide has been widely used in winemaking because of its antioxidant, antioxidasic and antiseptic properties. SO2 may appear in wine under different forms due to its acid‐base properties and to the more or less reversible adducts that it can form with acetaldehyde, sugars, polyphenols and other carbonyls. Speciation of this molecule is essential because its bioactive and antioxidant activities are extremely dependent on the specific chemical species. Total levels of SO2 are important because of safety and legal reasons. Bound sulfur dioxide represents a complex pool of diverse molecules from which free SO2 can be released. Such release, inevitably will have consequences on wine sensory properties, since the cleavage of SO2 adducts will release anthocyanins, and sensory relevant aldehydes [1]. Bisulfite (HSO3 ‐) is important due to its antioxidant and antioxidasic properties and molecular SO2 (SO2 plus H2SO3) is the most bioactive form and the main responsible for microbial stability. The reference method of aspiration/titration for determining free SO2 fails when levels drop below 7‐8 mg/L. Moreover, this method is based on an unspecific determination in which acid volatile compounds can produce interferences which can be important at low levels. Additionally, there are doubts about whether the free SO2 determined by the reference method is all equally active, because it has been shown that wines with similar levels of SO2 have different level of protection [2]. Three different methods based on GC‐MS have been developed for the speciation of SO2. Total forms are determined by HS‐GC‐MS of the acidified sample after incubation at 100ºC. Free and weakly‐bound SO2 is similarly determined but incubation is carried out at 40ºC. Similar results to the official method are achieved but limits of detection are much better (1 mg/L of free SO2) and the method is free from interferences. Finally, molecular SO2 is quantified also by HS‐GC‐MS analysis of an acidified fraction obtained by purging the wine with nitrogen and trapping SO2 in an aqueous alkaline solution (pH 11.5). Results have demonstrated that between 10 and 80% of the free SO2 measured by the reference method is in fact forming complexes with polyphenols which are cleaved during the analysis.
DescripciónTrabajo presentado en la XVI Reunión Científica de la Sociedad Española de Cromatografía y Técnicas Afines (SECyTA 2016), celebrada en Sevilla del 2 al 4 de noviembre de 2016.
URIhttp://hdl.handle.net/10261/148715
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