This field guide gathers the sensory clues that have helped us recognize possible wine faults in comparative tastings. An aroma on its own is rarely enough for a diagnosis. Its intensity, the wine style, storage history and the way the wine changes with air all matter. Some of these characteristics may be intentional or even welcome at low levels, while the same compounds can obscure fruit, structure and sense of place when they dominate.
Bottle Refermentation
Look for: Unexpected fizz, cloudiness, sediment movement or yeasty pressure.
This is only a fault when the wine was intended to be still and stable.
Brettanomyces
Look for: Barnyard, leather, bandage, smoky or medicinal notes.
Perception and tolerance vary, but strong examples suppress fruit and varietal character.
Cork Taint (TCA)
Look for: Damp cardboard, musty cellar, muted fruit.
Even low levels may present mainly as a loss of fruit rather than an obvious smell.
Diacetyl
Look for: Butter, butterscotch or popcorn.
It can be intentional after malolactic fermentation; it becomes a fault when it overwhelms the wine.
Excess Sulphur Dioxide
Look for: Acrid struck-match sensation, nasal irritation or a sharp sulphur edge.
Do not confuse this automatically with every smoky or flinty aroma.
Heat or Light Damage
Look for: Cooked fruit, stewed character, loss of freshness; light-struck wines may smell cabbage-like.
Storage history and closure condition help distinguish damage from deliberate style.
Mercaptans
Look for: Garlic, onion, cooked cabbage, rubber or skunky notes.
These sulphur compounds can develop when early reduction is not resolved.
Oxidation
Look for: Browning colour, bruised apple, nuts, stale or flat fruit.
Intentional oxidative styles exist; the question is whether oxygen exposure fits the intended wine.
Reduction / Hydrogen Sulfide
Look for: Struck match, rotten egg, cabbage or rubber.
Light reduction can dissipate with air; persistent sulphur compounds may not.
Volatile Acidity / Ethyl Acetate
Look for: Vinegar, nail-polish remover or solvent lift.
Small amounts can add aromatic lift, but high levels dominate fruit and balance.