Common Winemaking Problems


Stuck Fermentation

The yeast died before fermentation completed

Keep fermentation temp. below 90 degrees; dilute overripe fruit with water to 25 Brix; add nitrogen (DAP) and SuperFood; use vigorous yeast like Prise de Mousse

Cooked Flavors

Fermentation temperatures too high; overripe grapes; too many raisins

Ferment whites at 60 deg. Or less; ferment reds at 85 degrees or less; avoid overripe fruit

Burnt match odor

Sulfur dioxide gas

Keep free SO2 to less than 40ppm; use less SO2 in wines with low pH values

Sherry or Madeira odors

Oxidized wine

Keep all wine storage containers full and tightly sealed; use moderate amt. Of sulfur dioxide; avoid pumps with leaky shaft seals and avoid air leaks in pump suction lines

Swampy odors

Bad corks

Try changing cork suppliers

Rotten egg odors

Hydrogen sulfide gas

Avoid grapes with excessive sulfur residues; avoid Montrachet yeast; add nitrogen and nutrients early; avoid hot fermentation

Vinegar and fingernail polish odors

Acetic acid and ethyl acetate produced by Acetobacter bacterium

Keep containers full; use moderate amt. Of sulfur dioxide but Acetobacter tolerates SO2; remove pomace promptly; keep winery clean

Rancid butter odor

Excessive amount of diacetyl

Inoculate with ML bacteria early; control ML fermentation w/ SO2

Moldy or mildew odor

Moldy barrels; rotten fruit; mold in hoses & equipment

Avoid empty barrels/maintain them properly; avoid rotten, moldy grapes; hang hoses to dry completely; keep winery clean

Barnyard, horsy, mousy or wet-dog odors

Fermentation products produced by Brettanomyces film yeast

Keep containers full; maintain 30 ppm SO2; avoid unknown/used barrels; get rid of dirty smelling barrels; keep winery clean