Wine Troubleshooting

1. Stuck Alcohol Fermentation
Stuck alcohol fermentation – a condition in which yeast has not started becoming active or has prematurely ceased converting sugar in the grape juice into alcohol – is a very common occurrence. It is the result of one or more of the following factors: the grapes are too moldy, sugar concentration is too high, alcohol content is too high, fermentation temperature.

A good alcoholic fermentation requires a favorable environment for yeast to become active and to multiply. Otherwise, fermentation may fail to start or may stop before completion, resulting in a sweet, low-alcohol wine. Stuck fermentation is easily detected by measuring the sugar content with a hydrometer. The specific gravity (SG) of a dry wine should be 0.995 or lower. If it is above 1.000 and is too low or too high, free sulfur dioxide (S02) content is too high or the yeast lacks nutrients. Remains unchanged for more than a day, then your fermentation is most likely stuck. If you are making wine from grapes, first ensure that the grapes are
not moldy to avoid fermentation problems. Moldy grapes can deprive yeast of essential nutrients and cause fermentation to become stuck, or possibly not start. Discard as many of the moldy grapes as possible and, as an added precaution, add yeast nutrients to feed the yeast and add sufficient sulfite to obtain a minimum free S02 level of 50 mg/L.

Before inoculating (pitching the yeast into) the juice, determine its sugar concentration. Excessively high sugar concentration may inhibit yeast activity. If the SG is more than 1.110 (this would yield approximately 15 percent alcohol by volume), try fermenting progressively by inoculating a 10 percent juice volume first. Use an S. bayanus yeast strain such as Lalvin’s EC-1118 or Red Star’s Premier Cuvee, which are intended for high-sugar, high-alcohol fermentations. When the yeast becomes active and fermentation is vigorous, double the juice volume. Then double the juice volume repeatedly in this manner until the whole batch is fermenting. For example, if fermenting a 20-liter (5-gallon) batch, start with 2 liters 0/2 gallon) and then double the volume to 4 liters (1 gallon), 8 liters (2 gallons), 16 liters (4 gallons) until the whole batch is fermenting. This process is known as progressive fermentation. Note that, at best, you can ferment the wine to a maximum alcohol level determined by the yeast strain selected. If your juice has sugar with a potential alcohol level beyond the yeast’s range, the yeast will stop working at the maximum level, resulting in a wine with perceptible or excessive residual sugar. (See “The Strain Game,” Fall 2000, for a list of yeasts and characteristics.)

If you need to chaptalize juice – the process of adding sugar to increase the alcohol content – try to avoid over-chaptalizing to prevent stuck fermentation, and add sugar in stages. For example, divide up the total amount of sugar into five separate additions to avoid overwhelming the yeast. Then ferment progressively as described above. Different yeast strains have different environmental F (7° to 35° C), whereas Lalvin’s S. cerevisiae RC212 yeast has a range of 59° to 86° F (15° to 30° C). Therefore, check the temperature of the juice to be fermented and make sure it is within the range recommended by the yeast manufacturer.

If it is beyond the range, move the carboy outside to a cooler temperature and stir the juice gently to dissipate some heat. If the temperature is too low, move the carboy to a warmer area or wrap a heating belt around the carboy. Heating belts are available from winemaking supply stores for approximately U.S. $15. Stir the juice thoroughly and fermentation should then restart within 24 to 48 hours. Free S02 (sourced from the addition of sodium or potassium metabisulfite powder) plays an important part in preventing microbial spoilage and safeguarding wines against premature oxidation. Yeast has good tolerance to free S02; however, excessively high free S02 content can inhibit yeast activity. Maintain a free S02 level of 50 mg/L throughout winemaking to avoid any potential problems. If you suspect it is too high, perform successive vigorous rackings to reduce concentration.

You can use a sulfite test kit to measure the free S02 concentration in white wines or, preferably, take a wine sample to a test lab for more accurate results. Phenolic compounds in red wines skew the measurements, giving higher-than-expected readings. The services of a test lab will come in handy here.

Remember the simple rule of thumb for adding sulfite – approximately half of the sulfite weight will become free S02. For example, to increase the free S02 content by approximately 25 mg/L in a 5-gallon batch, you need to add roughly one-fifth of a teaspoon, or 2 Campden tablets. (For more details on free S02, refer to “Solving the Sulfite Puzzle” in the Winter 2000 issue of WineMaker. Also visit to download our Sulfite Calculator.) Fermentation can also cease when the yeast has run out of nutrients that are essential for yeast cells to multiply. If all other conditions are favorable, add yeast nutrients at the rate of 10 to 20 g/hL, and then stir. (For a guide to measuring wine additives, see page 25.) Fermentation should restart within 24 to 48 hours. Adding yeast nutrients at the same time as yeast inoculation is always good practice if you expect a sluggish fermentation.

If the above procedures fail to restart fermentation, try adding fresh yeast specifically recommended for stuck fermentation, or alternatively, use actively fermenting wine to inoculate the stuck batch. Inoculate a 5 percent juice volume and then ferment progressively. Aeration by stirring or pumping over will stimulate fermentation, which should restart within 24 to 48 hours.

2. Stuck ML Fermentation
Malolactic fermentation (MLF) is a secondary fermentation in which Malolactic (ML) bacteria convert the harsher malic acid into the softer lactic acid. This form of bacteria can be found in wines produced from grapes or fresh juice, and therefore MLF can occur naturally if all environmental conditions are favorable for the bacteria to become active. However, indigenous ML bacteria may impart undesirable off-flavors and unexpected results, and therefore, it is always best to add a commercial ML culture for more predictable results.

MLF can’t happen in concentrates and sterilized juices because the bacteria have been eradicated during the concentration or sterilization procedures. It’s also not recommended because most concentrates and juices are tartrate-stabilized prior to concentrating or blending processes, and therefore contain a very high proportion of malic acid. MLF would convert this malic acid to lactic, leaving the wine with little acid and a pH above 3.8, resulting in a flabby, soft wine susceptible to bacterial infections.

As with alcoholic fermentation, MLF requires favorable environmental conditions to complete successfully and may become stuck or sluggish under the following conditions: the free sulfur dioxide (S02) content is too high, the temperature is too low or too high, or the pH is too low.

Paper chromatography is the tool used to monitor MLF progress. Paper chromatography analysis is a “laboratory” procedure used to detect the presence of malic and lactic acids in wines. If malic acid is still present and MLF does not seem to progress, you should try to identify the probable cause and act promptly.

High concentrations of free S02, the maximum typically being between 5 and 15 mg/L, and low temperatures, typically below 64° F (18° C), can inhibit MLF. These values vary from one manufacturer of ML culture to another; therefore, follow instructions for the selected product.

To reduce the free S02 concentration by accelerating dissipation, rack the wine successively and vigorously until the desired concentration is achieved. This may require re-inoculating with fresh ML bacteria because many types of bacteria are anaerobic t and therefore need to be protected from air. Fill your fermentation vessels completely and seal them with a fermentation lock.

If the temperature is below or beyond the recommended range, move the carboy to an appropriate area, for example, in a closet or a garage for warmer or cooler temperatures, respectively. Alternatively, use a heating belt wrapped around the carboy to increase the temperature of the wine.

A low pH level can also negatively affect ML bacteria. The minimum pH value is typically around 3.2, although different bacterium strains will have different requirements. Add potassium bicarbonate at the rate of 1 g/L of wine for each 0.1 unit increase in pH required. For example, for a 5-gallon (20-L) batch of wine with apH of 3.2, 40 g (12 tsp.) of potassium bicarbonate is required to increase the pH to 3.4.

The performance of ML bacteria is greatly improved with nutrients. Carry out MLF with the fine lees (sediment), which will serve as nutrients. Once a week, gently stir the lees into suspension, being careful not to aerate the wine excessively. Stirring your wine vigorously will accelerate oxidation of ML bacteria and will potentially render these ineffective.

The industry standard for specifying rate of addition of ingredients or chemicals is g/L (grams per liter) or g/hL (grams per 100 liters). Small-scale home winemakers often do not find these practical because they do not have access to a good balance scale that’s able to weigh small amounts of ingredients. Using a balance is the preferred method to ensure accuracy; however, if one is not available, an alternative is to use a teaspoon to measure out the required volume.

If we know the weight (in grams) of 1 teaspoon of a particular ingredient, then we can easily determine the number of teaspoons required for a known volume of wine. The table below lists the weight of common ingredients used to solve wine-making problems, along with the recommended rate of addition, and the number of teaspoons or weight in grams required for a 5-gallon (20-liter) batch. For simplicity, 5 gallons has been rounded to 20 liters.

There is one caveat, though, in using teaspoons: These are not perfect measuring tools and can yield up to 20 percent error, depending on how tight one packs the ingredient in the spoon and on its coarseness. Always scoop up the ingredients from the container without applying too much pressure to avoid packing, and use level teaspoons. Follow this method to minimize the margin of error. The small error should be of no concern.

If you expect to conduct the MLF under adverse conditions, condition the ML inoculum using commercial apple juice – the kind containing no preservatives. Dilute the ML inoculum into an equal volume of apple juice. For example, if the manufacturer’s instructions require to rehydrate ML culture in 50 mL of distilled water, add this inoculum to 50 mL of apple juice. Loosely cover the container, ensuring that there is little air space, and let the inoculum stand for approximately three days before adding it to the wine.

To ensure a successful MLF, always use an ML-compatible S. cerevisiae yeast, such as Lalvin’s ICV/D-47, for the alcoholic fermentation. (For more details on MLF and paper chromatog-raphy, refer to “Malolactic Magic” on page 53 in this issue.)

3. Sulfur Smell

The dreaded, common sulfur smell found in problem wines is a result of over-processing with sulfite. It is easily detected by its distinctive pungent burnt-match smell, and, at high concentrations, it can become overpowering. Some people can detect it at a level as low as 50 mg/L.

If a sulfur smell is detected in the fermenter, aerate the wine by successive vigorous rackings until you can no longer detect it. If detected in the bottle, aerate the wine by decanting it into another container, and repeat until you can no longer detect the smell. In both cases, let the wine splash at the bottom of the container. As a rule of thumb, to prevent sulfur smell, try to maintain a nominal free S02 level of 50 mg/L throughout the winemaking, except when doing an MLF.

4. Rotten-Egg Smell
A rotten-egg smell in wines is caused by the presence of hydrogen sulfide (H2S), and may be cured depending on its intensity. If not treated early, H2S will react in the wine to form first into mercaptans, followed by disulfides – both are foul-smelling compounds that cause wine to spoil. The presence of either compound is practically irreversible in home wine-making. Extensive chemistry knowl edge and experience and access to analytical laboratory equipment and chemicals are required. Therefore, the best cure for H2S is prevention.

Vinification from grapes that have been over-treated with sulfur-based vineyard mildew and fungus inhibitors is a common cause of H2S in wines from grapes. Either test or have a lab determine the level of free S02 in the juice following crushing. If it is above 100 mg/L, reduce it by successive rack-ings until it is below this level. Some winemakers prefer to work with a maximum of 50 mg/L.

Red wines made from grapes are more prone to H2S problems because the juice is allowed to macerate with the grape skins, therefore diluting sulfite into the juice. In white wines from grapes, it is not a problem because the juice is not macerated with the skins.

Prolonged aging of wine in the presence of sulfur deposits – arising from burnt sulfur during barrel maintenance – in oak barrels will also cause H2S to form. Pressed red wine left on the gross lees for too long a period (more than 18 months), whether in glass containers, stainless-steel tanks or oak barrels, may also cause problems. If detected early, these faults can be easily corrected. Small amounts of H2S should not be of concern. In fact, cultured yeasts used to inoculate juice will always produce H2S during alcoholic fermentation, albeit in very small quantities.

In all cases, aerate the wine abundantly by racking it against the wall of the container to reduce the amount of H2S. This has the drawback of accelerating oxidation and has to be assessed against the severity of the H2S problem. Alternatively, or in addition, sulfite the wine at a rate of 50 mg/L and then filter to strip it of elemental sulfur. Repeat this procedure after 3 months depending on the problem’s severity.

5. Acetic Spoilage
In general, proper and timely sul-fiting and stabilization should prevent any oxidation problem. However, wines that are overly exposed to air will become oxidized, which will eventually cause acetic spoilage, or acetobacter.

Depending on the duration of air exposure, the problem can manifest itself as a strong vinegar smell. In the worst case, a white film will form on the surface of the wine – a condition known as mycoderma. These point to a serious problem in the winemaking equipment or to its improper use, to poor topping practice, or often, a pH that is too high.

A common cause of acetic spoilage is a poor seal from bungs that are not properly seated in the mouth of carboys or from defective fermentation locks that do not provide an airtight seal. Ensure that bungs and fermentation locks provide airtight seals, and fill locks with a sulfite solution made by dissolving sulfite at a rate of 3 table-spoons per gallon (4 L) of water. Always top up containers to maintain minimum headspace between the wine level and the bottom of the fermentation lock, or protect the wine with a layer of azote (nitrogen) or C02.

As pH increases, free S02 becomes less effective and therefore does not adequately protect wine against oxidation, which could lead to acetic spoilage and mycoderma. Particular attention is required for wines with a pH above 3.6. As a rule of thumb, target a free S02 level of approximately [(pH-3.0)xlOO] mg/L for red wines; for white wines add 10 to this value. For example, if a white wine has a pH of 3.4, the amount of free S02 should be [(3.4-3.0)xlOO+10]=50 mg/L.

Wine affected by advanced acetic spoilage cannot be cured. If it is slightly affected, there is still a chance to cure the wine. Try filtering it through double cheesecloth to remove all particles of the white film. Sulfite the wine to a level of 100 mg/L and bottle it immediately. It should be drunk as soon as possible.

6. Acidity and pH
Low total titratable acidity (TA) and high pFI, or high TA and low pH in wine, may be due to the grape variety used or a poor vintage, or may be the result of a chemical imbalance during vinification. These conditions can be handled with relative ease using products from your local winemaking supply shop. (Refer to “Acidity: A Balancing Act” and “pHiguring out pH” in the Spring and Summer 2001 issues of WineMaker.)

The more complex problems of high TA/high pH or low TA/low pH pose a greater challenge to home winemak-ers. Acid-reducing or pH-augmenting solutions can’t be used because these will correct one at the expense of the other. An exception is phosphoric acid, which can be used to lower pH with minimum increase in acidity. Follow the manufacturer’s instructions.

Another solution is to blend wines that improve both TA and pH levels. For example, a high TA/high pH wine can be corrected by blending it with a wine of normal TA and pH or low TA and pH. Unfortunately, this method requires stocking TA- and pH-unbal-anced wines, which can’t be stored for an extended time as they are also prone to spoilage problems. Quite often, the problem with a seemingly low TA is a sodium hydroxide (NaOH) titrate solution that has lost its strength. For example, its normality is no longer 0.1N or 0.2N when measuring the TA. There may be nothing wrong with the actual TA except for a false measurement, which means you should compensate for the weaker titrate solution. Determine the strength of your solution with potassium acid phthalate. Ask your winemaking supplier for this and follow instructions. Or simply buy fresh titrate solution.

7. Cloudiness
Cloudiness in a wine may result from improper racking, when sediment is disturbed and allowed to go into suspension, or from improper clarification, such as incomplete fining or filtering with too coarse a pad, or a high fruit pectin content. Cloudiness may reappear in perfectly clear and brilliant-color wines during aging. This will happen in wines that have not been properly stabilized. To reduce cloudiness, let the sediment settle to the bottom of the container and then carefully rack the wine. The wine can be clarified by fining, using your favorite fining agent, followed by another racking. Always allow a minimum of two or three weeks before racking. Optionally, the wine can be filtered, particularly if cloudiness persists.

Pectin may be another source of problems when making wine from grapes or fruits. A clear wine with high pectin content may cause the wine to turn cloudy in the bottle. Pectic enzymes can be used to reduce excessive pectin and potential cloudiness problems. Add pectic enzymes at the rate of 1 to 2 g/hL for white wines and 2 to 4 g/hL for red wines at the time of grape crushing. Be sure to dissolve the powder in cool water before adding it to the juice.

8. tartrate Crystals
When wine is subjected to cold temperatures – for example, around the freezing point of water – for a few days to several weeks, tartaric acid crystallizes and precipitates as tartrate crystals. Youmay have noticed this condition in a bottle of white wine forgotten in the refrigerator for a few weeks. These crystals look like little shards of glass but only affect the appearance of a wine and can be easily separated from wine by racking. They do not affect its taste, although total acidity and pH are affected.

To prevent tartrate crystals from forming in the bottle, cold stabilize the wine by placing it in cold storage at a temperature between 25° and 40° F (-4° and 4° C) for approximately 3 weeks. Alternatively, protect the wine from tartrate crystallization by adding metatartaric acid at a rate of up to 10 g/hL. Dissolve the crystals in cold water before adding the solution to the wine

9. Carbon Dioxide Gas
A fizzy wine indicates that carbon dioxide (C02) gas is still present, and that perhaps alcoholic or ML fermentations has not completed. If a wine had not undergone MLF because of cool cellar temperatures, MLF may be provoked if ML bacteria are still present and if the cellar temperature starts to rise. This explains why C02 bubbles reappear in the spring. As a first step, always let the fermentations complete as desired. For early-drinking wines, eliminate any small amount of excess C02 using a vigorous racking or by stirring the finished wine vigorously twice a day until there is no more C02 present. Ensure that the wine is adequately protected with sulfite to prevent accelerating oxidation. Another effective method uses an electric pump to remove excess gas. Shake the wine under vacuum while running the pump.

If C02 is detected in bottled wine and you determine that alcoholic or ML fermentation have not completed, pour all the wine from the same batch into a large vessel (bottles may explode if stored with residual gas) and let the fermentation complete. You may need to add nutrients, more yeast or bacteria to ensure successful fermentation.

10. Bitterness
A bitter, astringent sensation is a result of harsh or excessive tannins – a problem mainly associated with red wines. The root causes include: over-extraction of tannins from grape stems and seeds during crushing, maceration or pressing; or over-extraction of tannins from oak barrels or chips. Tannins will soften and reduce astringency over time but this requires many months or years of aging. To prevent over-extraction of tannins during winemaking, reduce or eliminate stems and stalks at grape crushing, and ferment free-run and press-run juices separately. Once the wines are completed and stabilized, blend them to achieve the desired tannin level.

If oak-barrel aging, reduce the aging period because oak will add tannins to the wine. Using a fining agent during the clarification process can reduce the tannin level. Egg whites or gelatin work best. Add egg whites at a rate of 5 to 10 g/hL, or the white from one egg for a 5-gallon batch. For each egg white, add a pinch of table salt to just enough water to dissolve it and then add this to the wine. Rack the wine within two weeks, no later. For gelatin, follow the manufacturer’s recommended dosage and instructions. Another effective method is to blend the highly tannic wine with a softer wine. If the tannin level is too low, you can add grape tannin at the rate of 10 to 30 g/L by first dissolving the powder in warm water. Or age the wine in oak barrels. Ensure that you maintain a proper balance between alcohol content and tannin level by tasting the wine. Highly tannic wines require a minimum alcohol level (between 12.5 and 14.0 percent alcohol by volume) to be properly balanced. If a highly tannic wine has a low alcohol level, use a high-alcohol-content tannic wine for blending.

11. Color
In white wines, poor color problems are often due to oxidation, resulting in a browning effect. To prevent browning during winemaking, always protect your white juice and wine from air, and adequately sulfite. In red wines, the typical problem is either a color that is too light or too dark. A light color in reds may be the result of a short maceration period when making wine from grapes, or from over-filtering. A dark color may be the result of a maceration period that was too long, especially if using dark-juice grapes such as Alicante Bouschet. Color is best controlled throughout all winemaking stages to achieve desired results. At grape crushing, reduce or eliminate stems and stalks to produce a lighter color. During maceration, monitor color extraction and proceed to pressing once the desired color is achieved. (See “Mastering Maceration,” Fall 2001.) Remember that, in general, wine will always lighten from the start of fermentation to a finished wine due to sedimentation of phenolic compounds (which have color), fining and filtration.

White wines that have started browning due to oxidation can be somewhat corrected using a casein treatment. Add casein at rate of 50 to 100 g/hL, depending on the extent of browning. Dissolve the powder in cold water and then add quickly to the wine while stirring vigorously. Follow this with a bentonite treatment at a rate of 25 to 100 g/hL. Casein may strip the wine of some of its aromas. As an alternative, you may use Polyclar at a rate of 25 to 75 g/hL to prevent aromas from being stripped.

Poor color in red wines can be corrected through blending. Choose a dark-colored wine when blending with light-colored wines for best results. If the color is excessively light, you may need to use a wine made from Alicante Bouschet, for example, which has a very deep color. If the color is too {lark, you can also let the wine age until the desired color is obtained, or you can filter the wine after fining. Aging and filtering always lighten the color. Another effective method that will add color to red wine is the use of powdered grape skin. Add powdered grape skin to light-colored red wine at a rate of 5 g/hL. Repeat the dosage until you have obtained the desired color. Make these additions before fining the wine to avoid having any bottle sedimentation due to the grape skin powder.

12. Geranium Smell
A geranium off-odor in wines is a serious fault that cannot be corrected. This odor is the result of a reaction between ML bacteria and sorbic acid, found in potassium sorbate (used to stabilize wines by inhibiting the growth of yeast and mold).
This problem is best avoided by eliminating the use of potassium sorbate in dry wines that will be ML fermented. In sweet wines, because it is recommended to add potassium sorbate to prevent bottle fermentation, avoid MLF and sulfite adequately when adding potassium sorbate.

Beer Troubleshooting

1. Oxidation
Oxidation results in a cardboard or paper/woody flavor. This is usually the result of air being introduced into beer after the fermentation process.

Oxidation produces undesired conditions, such as stale flavors, loss of hop aroma and flavor. You can slow down oxidation of your beer by avoiding picking up air on both ends of the brewing process, as well as with using yeasts and antioxidants.

The best way to minimize the possibilities of oxidation is to use an anti-vortex device to spread beer more evenly upon entry to the tank. Also, you can reduce the affects by making sure your tank doesn’t get sucked dry, creating a vortex. There are other ways to reduce the possibility of air contaminating your beer, covered in detail in the book.

2. Gushing
Overprimed bottles may gush when opened. Infections of yeast will also cause gushing. Excessive foam can also be caused by over-carbonation.

3. Harshness
A unpleasant, bitter taste on the back of your tongue can come from infection by wild yeast. In beers uninfected by wild yeast, mineral content in water can be a factor. There are several other factors including boiling hops to long, discussed in the book.

4. Haze
Caused by particles suspended in the beer, haze can be the result of bacteria, wild yeast, starchor other substances. By simply filtering your beer, you can remove the suspended particles. Usually a beer will have to be chilled and let stand for 24 hours before filtering, as chill haze is often a common problem. Sometimes haze may take months to develop.

5. Metal Distaste
Passivating copper parts with sodium citrate in a 1 percentsolution, followed by rinsing can help reduce oxidization and metallic tastes in your beer.

6. Must, Mold, Earthy Flavors
Algae in water can contribute to these flavors. Also, mold growth in open fermenters in in basements or cellars can cause this condition. Cracked beer hoses can also allow growth.

Pre-brewing checks and measures are most important to reduce chances of these conditions. You cannot filter out these characteristics, unfortunately.

7. Headless Beer
Usually the result of poor fermentation, headless beer can make even a tasty beer look unappealing. Strains of acetic acid can kill bacterial yeast and prevent fermentation.

Usually, the culprit is forgetting to prime your beer. The book goes into more detail about how to prevent this condition.

8. Skunky Beer
Without going into too much chemistry, skunky beer is the result of some agitated molecules combining to create the very same molecules skunks create to make their horrific smell. This is a direct result of light. Darker bottles help reduce this. Unfortunately, there is no cure for skunky beer.

9. Weak Body
Thin bodied beers often result from beers low in specific gravity. Infections can be another issue. Try using more grain or extra dextrin malt in the grist. Higher mash temperatures and the elimination of protein rest helps as well.