Geranium Taint

Lactic acid bacteria metabolize sorbic acid (a preservative) into 2-ethoxyhexa-3,5-diene, which has an intense geranium leaf/crushed geranium aroma. Only occurs when sorbic acid (potassium sorbate) is added to wines that then undergo malolactic fermentation or LAB contamination.

Distinct crushed geranium leaf or pelargonium aroma. Even at very low concentrations, the compound is intensely aromatic and unmistakable. Completely irreversible — the wine cannot be salvaged once affected.

Never add sorbic acid to wines that might undergo malolactic fermentation. Ensure ML is complete before adding sorbate. Sterile-filter before bottling if using sorbate. Some winemakers avoid sorbate entirely, using sterile filtration alone to prevent refermentation.