Evaluation of key odorants in sauvignon blanc wines using three different methodologies.

In this study three different approaches were employed to identify key odorants in Sauvignon blanc wines. First, the concentrations of the odorants were compared to their respective aroma detection thresholds. The resulting odor activity values (OAV) were transformed into a normalized and weighted measure that allows the aroma profiles of different wines to be compared and the contribution of a single aroma in a complex mixture to be evaluated. Based on their OAV, 3-mercaptohexanol and 3-mercaptohexyl acetate were the two most important aroma compounds in many Marlborough Sauvignon blanc wines. Due to limitations with the OAV approach, the study was extended to include aroma extract dilution analysis (AEDA), which revealed that ß-damascenone, together with the varietal thiols, esters, and higher alcohols, are key odorants in Sauvignon blanc wines. The final approach undertaken was aroma reconstitution and omission tests using a deodorized wine base and the creation of a model Marlborough Sauvignon blanc. Single compounds and groups of compounds were omitted from the model to study their impact on the sensory properties of the model wine. Reconstitution and omission confirmed that varietal thiols, esters, terpenes, and ß-damascenone are all important contributors to Sauvignon blanc aroma. The methoxypyrazines showed an important but relatively low impact in all three of the approaches undertaken in this study.

Effect of screwcap and cork closures on SO2 levels and aromas in a Sauvignon Blanc wine.

The development of a Sauvignon Blanc wine sealed under screwcap and cork was undertaken using different fill heights and initial levels of free SO2 (20, 25, and 30 mg/L) over 2 years. More SO2 was lost for wines under cork over the first 3 months, corresponding to a higher level of dissolved oxygen at bottling. From this time wines under cork and screwcap lost SO2 at a similar rate and retained dissolved CO2 equally well, indicating that both types of closure presented a similar effective barrier to gas movement. After 2 years in the bottle, the different treatments retained similar levels of the volatile thiols 3-mercaptohexyl acetate (3MHA) and 3-mercaptohexanol (3MH) responsible for fruity aromas, with initial SO2 levels having no effect, but the thiol concentrations were 18-23% lower under cork, which may be due to absorption of volatiles into the cork. Levels of polyphenols such as caftaric acid and the absorbance at 420 nm were the same for wines under cork and screwcap, whereas some indication was given that more oxidation occurred with a lower level of initial free SO2. Although the different treatments were not readily distinguished by a sensory panel, the data for individual wines showed a positive correlation between passion fruit descriptors and levels of 3MHA and 3MH.