• Description: Reduction results from the lack of oxygen during winemaking, leading to off-putting sulfur or rotten egg aromas. It can also cause a flinty or struck match odor.

• Source: Excessive use of sulfur dioxide, lack of aeration during winemaking, or the presence of unwanted microorganisms.

Reduction:**
   - **Description:** A sulfur or rotten egg smell caused by the presence of hydrogen sulfide or other sulfur compounds. It can evolve into more complex sulfurous odors.
   - **Source:** Excessive sulfur dioxide usage, poor yeast health, or