Troubleshooting Common Winemaking Problems

This is a guide to correct some of the common problems in winemaking.

Problem Possible Causes Corrective Action
The fermentation is stuck or sluggish

1. Temperature is too high or low

2. Sugar level is too high

3. Alcohol level is too high

4. Lack of oxygen

5. Lack of nutrients

6. pH is too low

7. Volatile acidity (VA) is too high

8. Low yeast count

1. Adjust temperature

2. Conduct a progressive fermentation

3. Use a strong fermenting yeast

4. Aerate the must/wine

5. Prepare and add additional nutrients

6. De-acidify and add fresh yeast

7. Reduce VA and add fresh yeast

8. Add fresh yeast

The color is too light

1. Light whites: Excessive fining and/or filtration

2. Light reds: Excessive fining and/or filtration, grape variety, or too short of a maceration.  It can also be the result of aging young, deeply colored wine with low tannin concentration.

1 and 2. Blend with other wines

2. Add grape skins powder, natural tannins, or add macerating enzymes prior to fermentation.

The color is brown and/or smells like sherry Oxidation due to defective or poor use of winemaking equipment, excessive exposure to air during processing or storage, or low sulfite levels

Lightly oxidized: Treat white wines with a fining agent, sulfite and then filter. Red wines should be left alone.

Heavily oxidized wine should be discarded, as there is no correction.

It smells of vinegar or nail polish remover, and/or has formed a white film The wine has been exposed to air causing an interaction with Acetobacter organisms (mother of vinegar) and/or the wine has low sulfite levels

There is no correcting.

For mild cases, drink the wine soon if tolerable.

For serious cases, discard the wine.

It smells of sulfur Overuse of sulfite and/or stressed yeast during fermentation

Aerate the must/wine by stirring or racking.

Treat with a dilute 3% hydrogen peroxide solution

It smells of rotten eggs or burnt rubber

1. Elemental sulfur on the grapes

2. Excessive use of sulfite

3. Contact with sulfur deposits in oak barrels

4. Lack of nutrients

5. Extended contact with gross lees

6. Yeast strain the produces high levels of hydrogen sulfide

For mild cases rack the wine and aerate

For serious cases, do not rack or aerate, but treat with a 1% copper sulfite solution. If no change treat with activated carbon.

It smells yeasty Wine has been in contact with lees for too long and autolysis has occurred

There is no correction.

Drink if tolerable, or dump if not.

It is cloudy

1. Incomplete fermentation

2. Improper racking/clarification

3. Wine is not protein stable

4. High pectin content

5. Ferric casse, the result of excessive aeration in high iron content wine

1. Allow fermentation to complete

2. Allow the wine to settle until clear and rack. Fine and filter as needed

3. Treat with bentonite

4. Treat with pectic enzymes

5. Fine/filter, then add ascorbic acid.

There are crystal deposits on the bottom (tartrate crystals) The wine has not been cold stabilized

Rack and cold stabilize the wine.

Rack the wine and add metatartaric acid

It is fizzy or carbonated

1. Residual CO2 gas is still in suspension

2. Incomplete fermentation

1. Degas the wine by racking, stirring, or using a vacuum pump

2. Allow fermentation to complete

It is too sweet

1. Incomplete fermentation

2. Wine is not balanced

1. Allow fermentation to complete

2. Increase TA to reach balance, or blend with another wine

There is an overly bitter taste

1. Extraction of "harsh" tannins from stems and seeds

2. Over extraction of tannins from grape skins or barrel aging

3. Wine is not balanced

1 and 2. Fine with egg whites or gelatin. Or blend with a less tannic wine

3. Reduce TA to achieve balance in the wine

It is hot and heady High sugar content must that was fully fermented Blend with a lower alcohol wine
It smells moldy or musty The result of a chemical reaction between phenol compounds in oak and wine, and mold or chlorine that produces TCA (trichloroanisole) No corrective  action, drink if tolerable, or dump if not
It has a strong barnyard smell Brettanomyces yeast infection

In wine, sulfite and stabilize filter

In a barrel, remove from service

It tastes of sour milk Lactobacillus or Pediococcus bacterial infection

 If the wine is drinkable, sulfite and stabilize filter, or dump if not


Chart courtesy of author Daniel Pambianchi -

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