Rainer Jung

Impact of Headspace Oxygen and Closure on Sulfur Dioxide, Color, and Hydrogen Sulfide Levels in a Riesling Wine

Following an experimental design replicating typical winery conditions, a Riesling wine was bottled with different headspace oxygen levels and sealed with either a coextruded closure or a screwcap to investigate the impact of headspace oxygen and closure oxygen transfer rate on wine evolution. Using luminescence technology, dissolved oxygen and headspace oxygen, as well as oxygen ingress through the closure, were monitored during 24 months of bottle storage. Under typical winery conditions, headspace oxygen introduced at bottling was found to be a major component of oxygen in bottled wine. Headspace oxygen at bottling influenced loss of sulfur dioxide during bottle storage, being the main cause of sulfur dioxide decline during the first four months after bottling in 375 mL bottles. The loss of sulfur dioxide was not correlated with the evolution of dissolved oxygen, but with the total amount of oxygen consumed by the wine. After 24 months in the bottle, color differences due to different headspace oxygen and closure oxygen transfer rate were generally minor. Conversely, differences in closure oxygen transfer rate were responsible for significant differences in the final concentration of the off-odor compound hydrogen sulfide, with screwcap generally associated with higher levels of this compound. Even if less significantly, the amount of oxygen present in the headspace at bottling also had an effect on final hydrogen sulfide, with higher concentrations observed in wines bottled with lower headspace oxygen.

Impact of Dissolved Oxygen at Bottling on Sulfur Dioxide and Sensory Properties of a Riesling Wine

A Riesling wine was bottled with different levels of dissolved oxygen and sealed with two different coextruded closures and one screwcap closure in order to investigate the impact of dissolved oxygen and of closure oxygen transfer rate on wine evolution. Dissolved oxygen introduced at bottling influenced sulfur dioxide decline during bottle storage, especially during the first three months. However, the loss of sulfur dioxide was more strongly correlated with the total amount of oxygen consumed by the wine rather than with the evolution of dissolved oxygen. Closure oxygen transfer rate also influenced sulfur dioxide loss, and this effect became greater with time in the bottle. Although closure was an important factor influencing sensory attributes of bottled wine, within each closure, dissolved oxygen accounted for significant differences across the wines. Wines bottled with high dissolved oxygen showed significantly higher ratings for oxidation, confirming the influence of dissolved oxygen management on the evolution of wine over time.

“Cork taint” responsible compounds. Determination of haloanisoles and halophenols in cork matrix: A review

Analytical methods of haloanisoles and halophenols quantification in cork matrix are summarized in the current review. Sample-preparation and sample-treatment techniques have been compared and discussed from the perspective of their efficiency, time- and extractant-optimization, easiness of performance. Primary interest of these analyses usually addresses to 2,4,6-trichloroanisole (TCA), which is a major wine contaminant among haloanisoles. Two concepts of TCA determination are described in the review: releasable TCA and total TCA analyses. Chromatographic, bioanalytical and sensorial methods were compared according to their application in the cork industry and in scientific investigations. Finally, it was shown that modern analytical techniques are able to provide required sensitivity, selectivity and repeatability for haloanisoles and halophenols determination.

Bottle capsules as a barrier against airborne 2,4,6-trichloroanisole

The possibility of 2,4,6-trichloroanisole (TCA) migration through synthetic stoppers and into wine from highly contaminated air was shown by several authors. However, those experiments were usually conducted without bottle capsules, which are a common part of wine packaging. In the current study, we demonstrated that the presence of capsules (without open holes) above synthetic stoppers can reduce wine contamination by airborne d5-TCA by about 10 times or more. Generally, metallic capsules revealed better barrier properties than polyvinyl chloride counterparts. Application of EVOH film on the external surface of the polyvinyl chloride capsules usually resulted in a lower level of wine contamination. Additionally it was demonstrated, that relatively short exposure (3 months) of the bottles to highly contaminated air could cause a considerable absorption of d5-TCA by synthetic stoppers, which can subsequently lead to wine contamination after 12 months.

Characterizing Dry Riesling Wines’ Aromatic Typicality with Sensory and Instrumental Analytical Methods – A Comparative Approach

A series of orthonasal sensory tastings was conducted by two sensory panels on 41 wines from different varieties to give a sensory concept of Riesling wines. In addition to this, aroma compounds, including thiols such as 3-sulfanylhexanol and 4-methyl-4-sulfanylpentan-2-one, were analyzed and correlated to sensory data. A sensory concept of Riesling wines, which correlated to certain sensory properties and aroma compounds, could be established.