Abstract
The main aim of the present work is to study the accumulation of acetaldehyde and Strecker aldehydes (isobutyraldehyde, 2-methylbutanal, isovaleraldehyde, methional, phenylacetaldehyde) during the oxidation of red wines, and to relate the patterns of accumulation to the wine chemical composition. For that, eight different wines, extensively chemically characterized, were subjected at 25°C to three different controlled O2 exposure conditions: low (10 mg L−1) and medium or high (the stoichiometrically required amount to oxidize all wine total SO2 plus 18 or 32 mg L−1, respectively). Levels of volatile aldehydes and carbonyls were then determined and processed by different statistical techniques. Results showed that young wines (<2 years-old bottled wines) hardly accumulate any acetaldehyde regardless of the O2 consumed. In contrast, aged wines (>3 years-old bottled wines) accumulated acetaldehyde while their content in SO2 was not null, and the aged wine containing lowest polyphenols accumulated it throughout the whole process. Models suggest that the ability of a wine to accumulate acetaldehyde is positively related to its content in combined SO2, in epigallocatechin and to the mean degree of polymerization, and negatively to its content in Aldehyde Reactive Polyphenols (ARPs) which, attending to our models, are anthocyanins and small tannins. The accumulation of Strecker aldehydes is directly proportional to the wine content in the amino acid precursor, being the proportionality factor much higher for aged wines, except for phenylacetaldehyde, for which the opposite pattern was observed. Models suggest that non-aromatic Strecker aldehydes share with acetaldehyde a strong affinity toward ARPs and that the specific pattern of phenylacetaldehyde is likely due to a much reduced reactivity toward ARPs, to the possibility that diacetyl induces Strecker degradation of phenyl alanine and to the potential higher reactivity of this amino acid to some quinones derived from catechin. All this makes that this aldehyde accumulates with intensity, particularly in young wines, shortly after wine SO2 is depleted.
Highlights
Oxygen is a key factor to achieve wine optimum quality (Ugliano, 2013)
In all cases data correspond to total carbonyls, since methods used for their determination involved a previous step to break reversible adducts, such as those formed with sulfur dioxide
The pattern of accumulation of acetaldehyde in red wine during oxidation is related to the wine content in SO2 and SO2 binders, to the relative rates at which H2O2 and SO2 are formed and consumed, respectively, and to the wine content in Aldehyde Reactive Polyphenols (ARPs), which attending to our models, should be mostly anthocyanins and small tannins
Summary
Oxygen is a key factor to achieve wine optimum quality (Ugliano, 2013). Some of the improvements linked to an optimized use of oxygen are color stabilization (Ribéreau-Gayon et al, 1983; Atanasova et al, 2002a; Cano-Lopez et al, 2008; Wirth et al, 2010), the balance of astringency, bitterness, and mouthfeel (Cejudo-Bastante et al, 2011; Chira et al, 2012), and the decrease of vegetal and green aromas (Ortega Heras et al, 2008; Cejudo-Bastante et al, 2011). It removes H2O2 by reducing it to water (Danilewicz, 2003) and blocking Fenton reaction, and it can react with the quinones either reducing them back to catechols or forming a sulfonate as nucleophilic addition product (Waterhouse et al, 2016)
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