| Sensory properties of four important volatile sulfur compounds, dimethyl disulfide (DMDS), diethyl disulfide (DEDS), methanethiol (MeSH) and ethanethiol (EtSH), were determined in base Oregon Pinot noir wine in order to understand their impacts on wine aroma. Detection thresholds of these four compounds in base wine were determined first. All four compounds were found to have very low detection thresholds (in ppb) in base wine. Group thresholds of DMDS ranged from 11.18 to 23.57 ppb, those of DEDS ranged from 1.45 to 2.16 ppb, those of MeSH ranged from 1.72 to 1.82 ppb and those of EtSH ranged from 0.19 to 0.23 ppb. Subjects' abilities to detect these compounds in Pinot noir wine were very different. Aroma characteristics of the four compounds as well as their interactions in base wine were profiled via descriptive analysis. Aroma of DMDS in base wine was mainly described as old cabbage and rotten cabbage. DEDS aroma in wine was perceived as skunky, sweaty, and tire-like. Aroma of MeSH in wine was associated with stale vegetables, animal, rubbery, and slop. EtSH aroma in base wine was mainly described as durian, garlic, stale eggs, and natural gas. Odor suppression was observed when two or four sulfur compounds were mixed together in base wine. Perceiving off-odors in base wine was driven by MeSH and EtSH when both MeSH and DMDS or both EtSH and DEDS were present. EtSH affected wine aromas more when both MeSH and EtSH were present in base wine; however, MeSH governed wine off-odors more than EtSH under the influence of subthreshold levels of two disulfides. Mercaptans can significantly affect aroma quality of Oregon Pinot noir wine at very low concentrations (in ppb level); they have a stronger effect than disulfides. Regarding the impacts of base wine aromas caused by the four sulfur compounds, base wine lost its fruity and floral character and increased overall intensity, overall stinky, nose burn and sulfur-related odors while concentrations of the four volatile sulfur compounds in base wine increased. Aroma changes of fruity, floral and nose burn can be used by winemakers to diagnose the early presence of volatile sulfur compounds in Oregon Pinot noir wine during winemaking and wine storage. |
