What are the chemical precursors to hydrogen sulfide (H2S) formation in wine and how can its production be prevented?

Hydrogen sulfide (H2S) is a volatile sulfur compound that can cause unpleasant aromas in wine, often described as rotten eggs, garlic, or rubber. Several chemical precursors contribute to H2S formation during fermentation. One primary source is the reduction of elemental sulfur. Elemental sulfur is sometimes used in vineyards to control powdery mildew. If sulfur residues remain on the grapes, yeast can reduce it to H2S during fermentation. Another major precursor is the degradation of sulfur-containing amino acids, such as cysteine and methionine, by yeast. Under anaerobic conditions, yeast can cleave these amino acids, releasin....