Port wine Sotolon formation

Hence the aim of this work was to (/) evaluate the impact of Sotolon on the perceived age of Port wine (ii) determine which parameters (e.g. temperature, dissolved oxygen, pH and free SO2 content) have the greatest effect on Sotolon concentration, (Hi) and to establish mathematical models describing the rate of formation of Sotolon during storage, taking into account the critical parameters selected. 

The presence of 2-ketobutyric acid in Port wine was investigated (P). Although the quantities found could reach 2 mg/L, these were always lower than 0.5 mg/L for wines older than 10 years. No correlation between the levels of keto-acid neither with age nor with the amount of furanone could be found. Conversely a very liigh correlation was observed with acetaldehyde (r=0.8906). Thus, 2-ketobutyric acid may contribute to Sotolon formation, but taking into accoimt the linear trend observed with time for the Sotolon levels, it seems unlikely that this keto-acid constitutes the only source of Sotolon in Port wine. 

Kinetics Studies After determining tlie parameter witli the highest effect upon Sotolon concentration in port wines, attempts were made to establish a matliematical model, which reflects tlie impact of oxygen level, temperature as well as the time of storage, on the rate of formation of Sotolon. 

The Sotolon formation was studied as a function of temperature, pH, SO2 and oxygen concentration. Temperature and to a lesser extent, dissolved oxygen were tlie most important parameters influencing the rate of Sotolon formation. A first order model was applied and the Arrhenius equation described well the temperature dependence of the reaction rate constant. Therefore, oxygen levels during aging have a major impact on age perception" in Colheita and Vintage Port wine. 

Certain heterocyclic compounds are also important aromatic substances in wines, such as pyrazines in Cabernet Sauvignon and Sauvignon Blanc wines (see Section 8.2.11.1.7) and both enantiomers of 3-hydroxy-4,5-dimethyl-5if-furan-2-one (sotolon), which occur in white wines, sherries and are a key component of the typical aroma of aged Port wines. The precise chemical reactions leading to the formation of bouquet substances are not yet widely known. There are two types of reactions that produce bouquet constituents oxidation, which is characterised by the presence of aldehydes and acetals (e.g. in Madeira-type wines) and reduction (such as in quality table wines after a period of bottle maturation the flavour of low-quahty wines does not improve under the same conditions, but instead maturation often leads to a loss of freshness). During wine aging, glycosides of terpenic alcohols and... 

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