Sherry wines acetaldehyde

Aranda, A., Querol, A., del Olmo, M. (2002). Correlation between acetaldehyde and ethanol resistance and expression of HSP genes in yeast strains isolated during the biological aging of sherry wines. Arch. Microbiol., 177, 304-312. 

The wine yeast, Saccharomyces fermentati, is able to form a film or veil on the surface of dry white wines of about 15-16% alcohol. This yeast produces agreeable smelling and tasting substances which dissolve in the wine and give it the aroma and flavor characteristic of Spanish fino sherries. To provide itself with energy for growth while in the film form on the surface of the wine, the yeast utilizes some of the oxygen from the atmosphere above the wine in the partially filled butt or barrel to oxidize some of the ethyl alcohol from the wine. The ethyl alcohol of the wine is not completely metabolized to carbon dioxide and water, however, but is oxidized to acetaldehyde—probably the principal compound in the complex mixture responsible for the aroma of this type of appetizer wine. 

The combination of oxygen and flor yeast in a suitable shermat results in yeast growth and production of acetaldehyde. The wine passes through many taste and aroma phases during this process. The process is very flexible and can be used to produce anything from a pleasantly aromatic wine at 200 mg/L aldehyde to a strongly flavored flor sherry at 700 mg/L aldehyde to an intensely flavored flor with a long aftertaste at 1000 mg/L aldehyde. 

Chemical oxidation reactions and Strecker degradation of amino acids may also result in aldehyde formation (16). These reactions are important for the formation of acetaldehyde in baked or heated Sherries. Chemical oxidation reactions catalyzed by metal ions (Cu, Fe, Mn, Mo) can result in aldehyde production in oak aged distillates (20). Such reactions may also result in the formation of oxidation products from fatty acids released during the secondary fermentation of sparkling wines (21). 

Aldehyde Levels in Different Varieties and Styles of Wine. The derivatization procedure described above was used to determine aldehyde levels in several different wines (Table 4). The wines were made in the UCD Department of Viticulture and Enology winery using standard procedures. As expected, acetaldehyde was the predominant aldehyde in all samples, with highest levels observed in the Sherry (Table 3). The acetaldehyde concentrations are consistent with those obtained by enzymatic analysis of acetaldehyde in table wines and Sherries (38). 

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