Issue link: http://winesandvines.uberflip.com/i/417249
66 p r a c t i c a l w i n e r y & v i n e ya r d d e c e M B e r 2 0 1 4 W I N E M A K I N G closure OTR. Both hydrogen sulfide (H 2 S) and meth- anethiol (MeSH) also appear to be influ- enced by the closure used to seal the wine, with noticeable differences over 36 months in both white and red wine trials (Figures 6 to 9). In the red wine trial, levels of both of these compounds were largely undetect- able for the first 12 months of storage— but then increased during the second 12 months of storage—before again dropping during the third 12 months of storage. In the white wine trial different patterns emerged, with MeSH levels increasingly significantly during the latter stages of storage. This highlights the fact that these important sulfur-containing compounds are strongly influenced by the wine matrix and its individual chemical components. Trend concerns While these results relate only to the specific trial wines, the trends observed should concern winemakers. H 2 S levels can be seen climbing above the sensory- detection threshold of 1 µg/L under all closures for both red and white wines at some point during storage. Levels of MeSH approach the sensory detection threshold in the red wines but in- 10 8 6 4 2 0 21 22 23 DMS concentra on (µg/L) Free SO 2 (mg/L) 24 25 Figure 4: Correlation of free SO 2 loss between six months and 36 months with DMS concentration in red wine under different closures after 36 months. 16 14 12 10 8 6 4 2 0 14 14 15 15 16 16 DMS concentra on (µg/L) Free SO 2 (mg/L) Figure 5: Correlation of free SO 2 loss between six months and 36 months with DMS concentration in white wine under different closures after 36 months.