Sooner or later everyone encounters a wine problem. I only know one person who has made wine for years who claims to have never had one, and I tend to believe he interprets the word "problem" differently than most of us do. Listed below are some of the problems you might encounter. Don't let the number of such disorders scare you. You may encounter the more common problems, but it is unlikely you will ever encounter more than two or three of the remaining ones in a lifetime of winemaking if you use good ingredients and practice good sterilization procedures.
Fermentation Won't Start: A must that will not even begin fermentation could have a problem with the yeast, problem with the must, or both. Seldom will the yeast be so old that it is outright dead, although one might rarely buy a yeast that was stored or shipped improperly and died as a result of exposure to extreme heat. More often than not, however, the yeast itself isn't the problem. The problem is usually with the must.
Overly Sweet Wine: This is the bane of the beginning winemaker and by far the most common wine problem. An overly sweet wine can be corrected in two ways; you can restart fermentation and convert the residual sugar into alcohol or you can blend the sweet wine with a like wine that is bone dry, if you have it. In the first case, restarting fermentation may be a problem in itself. Use a fresh yeast with a high alcohol tolerance and sprinkle it over a sample of 1/2 cup of the overly sweet wine mixed with one cup of warm water into which 1/2 teaspoon of yeast nutrient has been dissolved. When fermentation begins in the sample and becomes very active, add 1/4 cup more wine. Wait 6-8 hours and add another 1/4 cup of the wine. Repeat this two more times. After another 6-8 hours, assuming the fermentation is still going strong, add the sample to the bulk of the overly sweet wine, stir in another 1/2 teaspoon of yeast nutrient, and fit the airlock in place. Rack after fermentation has ceased and again after 30 days. The resulting wine will contain more alcohol than before, but the excessive sweetness will be gone.
It is worthwhile to know why the wine is overly sweet in the first place so as to avoid the problem in the future. One of the easiest ways for an American to end up with overly sweet wine is to follow the original recipes from C.J.J. Berry's First Steps in Winemaking. Berry used imperial gallons in his recipes and we use U.S. gallons, which are smaller by one-fifth. If one doesn't adjust the sugar downward to account for the reduced volume, the result will be overly sweet wine. Also, Berry's recipes tend to contain the maximum amount of sugar that most wine yeasts can manage in the first place, and some yeasts simply cannot endure such sweetness well; this is certainly aggravated if you are using American gallons without adjusting the sugar downward in the first place. You can either (1) reduce the amount of sugar used by 1/5 the weight listed, (2) add the sugar to the must in stages (initially use 1/2 the recipe amount to the primary, then add half the remainder when transferring the wine to the secondary and the remaining half three days later), or (3) use a yeast with high alcohol tolerance. The best strategy when using Berry's original recipes is to take all three corrective measures. Berry's recipe's listed on this web site have been adapted to U.S. standards.
Another cause of overly sweet wine is a fermentation that stops early because of a lack of nutrition for the yeast. Always add at least 1/2 teaspoon of yeast nutrient per gallon of wine to your must, even if the recipe doesn't call for it. A full teaspoon is often called for in recipes. This amount is usually sufficient.
If you correct overly sweet wine by blending with an equal amount of dry wine, you will end up with sweet wine. This is a fact of life. If you do not like sweet wine, either try the first remedy (restart fermentation), blend one part of overly sweet wine to three or four parts of dry wine, or give the sweet or overly sweet wine to friends who appreciate it.
Commercial juices and musts are often heavily sulfited to ensure that fermentation doesn't start during storage and shipment. These musts are difficult to initiate fermentation, but once started they will ferment to dryness just as any juice or must will. If you have such a juice or must, initiating fermentation is a chore, but not a difficult one. First pour the juice or must into a primary fermentation vessel large enough to accommodate it. Then pour some or all of it into a polyethylene bucket and then back into the primary. Repeat this several times. This aerates the must, adding oxygen while encouraging the sulfites to discharge sulfur gas. Add 1/2 teaspoon yeast nutrient to the must and stir it in well. Then set aside a cup of the must and cover the primary with muslin, plastic wrap, etc. Add two cups of warm water and another 1/4 teaspoon of yeast nutrient to the cup of must and stir. Sprinkle a packet of wine yeast over the top of the diluted must, but do not stir or mix it in. Cover with muslin or plastic wrap and wait. It should begin fermenting within a day or two. When the fermentation is very active, add 1/2 cup of the undiluted must to the starter and wait 6-8 hours, then add another 1/2 cup of the undiluted must. Wait another 6-8 hours and gently add the fermenting starter to the primary. The fermentation should hold.
Sometimes a recipe will call for 2-1/2 to 3 cups of sugar per gallon. If added all at once, the must may become too sweet for some yeasts to activate. Fermentation occurs when liquid containing soluble sugar and trace nutrients passes through the cell walls of yeasts, is acted upon by enzymes and consumed, and alcohol and carbon dioxide are expelled through the cell walls as waste by-products. If the specific gravity of the must is too high, the alcohol and carbon dioxide cannot be expelled through the cell walls and the yeasts die of self-inflicted toxic poisoning. Thus, when adding large amounts of sugar per gallon to the must, it is always better to add half initially and the remainder in stages a few days apart. In this way the S.G. is never raised so high as to threaten the yeast, but the required sugar is still delivered.
Stuck Fermentation: A stuck fermentation is one that has started and then stopped prematurely. This is usually caused by a lack of nutrients or acid, but not sugar, or a change in temperature disagreeable to the yeast.
When a fermentation sticks, you need to begin taking measurements of the must to determine what the problem is. Often these will reveal an obvious problem--very low acid, for example--but on rare occasions there may be several things wrong and none of them obvious. Always correct an acid deficient must with acid blend as opposed to citric or tartaric acid alone. It doesn't hurt to add yeast nutrient (1/2 teaspoon per gallon of must) and yeast energizer, too (1/4 teaspoon per gallon of must is sufficient).
After correcting perceived deficiencies and bringing the must to 70° F., wait three days for the fermentation to restart. If it does not, set aside 1/2 cup of must and add to it a cup of warm (100¦ F.) water. Over this sprinkle a good yeast known to do well at restarting stuck fermentations, such as Red Star Premier Curvee (also known as Prise de Mousse) or Lalvin K1-V1116 (also known as Montpellier). Cover the sample and allow up to two days to begin fermenting (it will probably start fermenting within hours, but give it time if it doesn't). When the fermentation is vigorous in the sample, add 1/2 teaspoon of yeast nutrient and another 1/2 cup of must from the bulk batch. Stir the sample to dissolve the nutrient, recover, and set aside about 6 hours. If fermentation is still vigorous, add another 1/2 cup of must, recover, and wait 6 hours. If fermentation is still vigorous, gently add half the starter to the bulk must so the starter sort of lays on top of the must. Do not stir. Wait 24 hours and stir shallowly. Wait another 24 hours and stir deeply. If must does not ferment with starter added, add another 1/2 cup to the remaining starter and recover. After 6 hours, add another 1/2 cup of must. Wait 6 hours and follow directions for adding to bulk must.
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Colored Haze: The use of copper, zinc, iron, or aluminum implements or primary fermentation vessels can cause white, dark, purplish, or brown hazes. If the culprit was iron or copper, a few drops of citric acid will usually clear the haze. If zinc or aluminum, try fining with egg shell (see Finishing Your Wine); if that does not work try filtering. If that does not work either discard the wine or live with its color. Such hazes can only be avoided by scrupulously avoiding implements containing the offending metals.
Darkening Wine: A finished wine poured in a decanter turns dark after 24 hours. This can be caused by oxidation or because of enzymatic actions. In either case, the wine is not stable and should be stabilized by adding two crushed Campden tablets to each gallon of the wine. This can be a chore if the wine has already been bottled, but it can be done. This is also a symptom of iron contamination, which can be corrected by adding 1/2 ounce of citric acid to 5 gallons of wine. For a gallon of wine, add just under 1/2 teaspoon citric acid.
Failure to Clear: If you boiled ingredients to extract flavor, color or both and your wine fails to clear, you most likely have a pectin haze (see Pectin Haze below). If your wine is made from starchy ingredients, especially grains or tubers, that were boiled and pressed through a nylon straining bag and then fails to clear, you most likely have a starch haze (see Starch Haze below). If your wine has an off-color haze that fails to clear, you probably have a metal contamination (see Colored Haze below). If you have a haze following a malo-lactic bacteria inoculation, you probably have a lactic acid bacteria haze (see Lactic Acid Bacteria Haze below). If none of these apply and your wine fails to clear after six rackings at 30-day intervals, you simply have a nonspecific cloudy wine. Unless there is a bacterial contamination at work, the wine will probably clear but may take up to a year to do so. If you don't care to wait that long, there are several things you can do.
Move the wine into a cooler place for several weeks. All that is required is a drop in temperature of 10° F., but if the wine is over-heated in the first place (80° or more) you may have to bring the temperature down 20° or more.
If the above doesn't work, you might try using a fining agent. Most of these effect the taste of the wine somewhat, but I've found that mineral finings (Bentonite or Kaolin) effect it less than gelatin, egg whites or alkaline alginates. For a thorough discussion of fining agents, see Finishing Your Wine.
The wine may fall clear if you add a clear wine of the same type to it. The exact amount to add is open to discussion, but most authorities say to add 25% of the volume of the cloudy wine, or one quart clear per gallon of cloudy wine. This doesn't always work, but it's worth trying before progressing to filtering.
Filtering definitely effects the taste and character of the wine and can ruin it if too fine a filter is used, but sometimes it is the only option left. Borrow, rent or buy a vacuum-pumped filter. They are fast, efficient and will clear almost any wine if the correct filter pad or paper is used. Gravity filters take a long time to work and expose the wine to the risk of oxidation. Just be forewarned before using a filter that doing so can change the wine and possibly ruin it.
Lactic Acid Bacteria Haze: If you inoculated your wine with a malo-lactic bacteria and it develops a haze that is revealed as a silky sheen when the secondary is swirled, you have a lactic acid bacteria haze. When you are sure the malo-lactic fermentation is complete, treat with 3 crushed Campden tablets per gallon of wine, wait 10 days, and rack.
Off-Colored White Wine: A slightly misty or off-color white wine can often be clarified and decolored using egg shells. Egg shells are first cleaned and then dried in an oven. This makes them brittle. They are then easily crushed into very small pieces and these are stirred into the wine. They will slowly sink and over time collect carbon dioxide bubbles absorbed in the wine. These will cause the egg shell particles to rise and eventually leave the captured bubbles at the surface, thereby allowing them to sink again. This process may go on for some time. These tiny bits of agitated calcium slowly absorb off-colors and drag suspended particles to the bottom. I have found they are better at correcting the color than at clarifying the wine, but they do have an effect and don't seem to change the taste.
Pectin Haze: The most common cause of a haze in wine is the presence of pectin, which forms gelatinous solutions in the wine. The problem is aggravated if the must is initially boiled to extract flavor, color or both. To check if a haze is pectin in origin, add 3-4 fluid ounces of methylated spirit to a fluid ounce of wine. If jelly-like clots or strings form, then the problem is most likely pectin and should be treated.
To treat the wine, for each gallon of wine draw off one cup of wine and stir into it teaspoon of pectic enzyme. Set the treated sample in a warm place (70-80° F.) and stir hourly for four hours. Strain the sample through sterilized muslin cloth and add to the bulk of the wine. Leave the wine at 70° F. for 4-5 days. The haze should clear. If it does not, strain the wine through sterilized muslin cloth and then through a vacuum-pumped filter. If it still does not clarify, the problem was misdiagnosed.
Pectin hazes can be prevented by adding pectic enzymes to the must 12 hours before adding the wine yeast. One teaspoon of enzyme per gallon of must is usually enough, but some musts require 1-1/2 teaspoons.
Starch Haze: Starch hazes form when starchy materials used to make wine are misused, usually by boiling them too long or squeezing their pulp too severely to extract additional flavor. Starch haze is tested by adding 5 drops of iodine to 8 ounces of wine. If starch haze is present the wine will turn indigo blue. Treat with Amylase or Amylozyme 100. Amylase is used just like pectic enzyme is used to treat pectin haze. For each gallon of wine draw off one cup of wine and stir into it teaspoon of Amylase . Set the treated sample in a warm place (70-80° F.) and stir hourly for four hours. Strain the sample through sterilized muslin cloth and add to the bulk of the wine. Leave the wine at 70° F. for 4-5 days. The haze should clear. If it does not, strain the wine through sterilized muslin cloth and then through a vacuum-pumped filter. Amylozyme 100 is used differently. Treat with 1/2 ounce Amylozyme 100 (one tablespoon) per gallon of wine and bring into a warm room (70-75° F.) for a week. The wine should clear.
Parsnips, potatoes, turnips, grains, apples, pears, or any starchy material can produce a haze. A number of recipes warn the reader to put the material in a nylon straining bag and later to drip drain the ingredient or very lightly press it. These instructions almost always accompany ingredients which produce starch hazes and the reader will have no problem if the directions are followed.
Cork Taint ("Corked" Wine): A set of undesirable smells or tastes primarily caused by the presence of 2,4,6-trichloroanisole (TCA) in the wine and possessing a characteristic odor, variously described as resembling a moldy newspaper, wet dog, damp cloth, or damp basement. Very tainted wine is undrinkable, but otherwise harmless. Caused by airborne fungi that come in contact with chlorophenol compounds, a class of industrial pollutant found in many pesticides, which they then convert into chloroanisole. However, chlorophenols can also be produced by sterilizing corks in chlorine. Conventional wisdom has always been that a tainted wine cannot be corrected, but a professor at UC-Davis claims it can be by pouring the wine into a bowl containing a sheet of plastic wrap. The TCA molecules are chemically similar to polyethylene and stick to the plastic wrap within a few (10-15) minutes.
Fingernail Polish Remover Smell: The wine is contaminated with ethyl acetate. There are three ways a wine can become thus contaminated. (1) Ethyl alcohol and oxygen can interact to create acetaldehyde, which can react with oxygen to create acetic acid (vinegar), which in turn can react with ethyl alcohol to create ethyl acetate. This pathway can be easily shut down by preventing oxygen exposure with the wine. Since this is impossible, one can at least minimize it to what is absolutely necessary (racking, stirring, testing, bottling). This can be done by topping up adequately, using an inert gas (such as argon -- or even CO2) to sparge the new carboy of oxygen when racking, leaving the bung on the carboy except when absolutely necessary to break the seal, and keeping sulfur dioxide levels sufficiently high that no vacant molecular interstices exist for oxygen to populate. (2) Bacterial contamination of the wine (by acetobacter) can allow the creation of acetic acid, which then combines with ethyl alcohol in the wine to form ethyl acetate. The key to prevention, again, is maintaining an aseptic level of sulfur dioxide to preclude contamination and/or prevent contamination the same way oxygen exposure is prevented. (3) Finally, ethyl acetate contamination can be created by yeast under stress as well as by many bacteria besides acetobacter. In the first instance, maintaining an optimal temperature for the yeast strain employed, using a good mineral water in the must (if water is even used), yeast nutrient for non- grape wines, and a nitrogen source (Yeastex-61 or some other specialized nutrient) for yeast strains requiring ample nitrogen (see Strains of Wine Yeast) will eliminate yeast stress. In the second instance, if you follow the procedures for preventing acetobacter contamination, you will prevent the others as well.
In many cases of ethyl acetate contamination, running a small aquarium pump through an airstone "blows" ethyl acetate away in just a few days. Of course, the wine usually oxidizes during this treatment but can be consumed quickly or converted into a fortified wine in which oxidation is a requirement (such as Sherry or Madeira-type wines). In more severe cases, the ethyl acetate will be blown off only to reveal excessive acetic acid. When this occurs, the wine cannot be saved.
Flat Taste: Absolute flatness is symptomatic of insufficient acid in the wine. Add 1/8 teaspoon of tartaric acid and stir into wine. Refit airlock and wait 2-4 hours. Taste. If not vastly improved, add another 1/8 teaspoon of tartaric acid and stir again. Continue until the wine tastes right to you. Alternatively, you could blend the flat wine with an overly acidic one.
Mannite : A serious disease of wine, characterized by a very bitter taste, caused if a very high proportion of d-mannite (loosely termed mannitic bacteria or mannite) is produced by the action of the lactic acid bacteria on sugars. This can occur when there is too little acidity or when too much heat is generated during malolactic fermentation and the fermentation ceases. This condition only develops readily in wines after alcoholic fermentation has ended, The use of S02 and cooling have practically eliminated this spoilage, which, when severe, renders the wine undrinkable.
Medicinal Taste or smell: The wine has a medicinal taste, caused by too little acid in the must during fermentation. This occasionally occurs when an ingredient normally containing sufficient acid just happens to be acid deficient. While you can add acid to the wine and correct the acidity, that may not correct the medicinal taste. If that is the case, all you can do is make a note to test for acid next time you use that recipe.
Medicinal odors can be caused by several things, but the most common is a number of compounds created by the yeast Brettanomyces bruxellensis (simply "Brett" in most conversations) and its anamorph relative Dekkera bruxellensis. My experience with home wines is that three things may help if the odor is not too strong. The obvious first step is to raise the sulfur dioxide (potassium metabisulfite) level of the wine to an aseptic level to arrest the growth of Brett, treat with activated charcoal for 3 to 8 weeks, and sterile filter (0.45 microns or less) to remove residual yeast cells. If the Brett infection is strong, the drain is the answer.
Metallic Flavor: Rarely, the use of canned (tinned) fruit or berries or even juices can result in a metallic taste to the wine made from such ingredients. This occurs when a highly acidic ingredient sits too long in an poorly tinned can and absorbs flavors from acid-metal interaction. This is not a common occurance, but the taste does spoil the wine. Nothing can be done to correct this off-taste, but you can avoid the offending brand in the future.
Musty or Moldy Taste: This is caused by wine standing too long on the lees without racking. It can also be caused by using baker's yeast instead of wine yeast. Add one crushed Campden tablet and 1/2 ounce of activated charcoal to each gallon of wine and stir with a sterile rod. Allow to settle 4-6 hours and stir again. Repeat the stirring procedure 4-6 times and then let sit undisturbed 24 hours. Rack through a double layer of sterilized muslin to catch minute charcoal particles.
Plastic Taste or Smell: This is caused by using a non-food- grade plastic container for the primary fermentation. The most common culprit is the household trash can or waste basket. Follow the procedure for Musty or Moldy Taste , but don't be too hopeful. There is a reason they make food-grade plastic.
Rotten-Egg Smell: Hydrogen-sulfide gas manifests itself as the smell of rotten eggs. Pour the must or wine from one container to another for a few minutes to aerate it. Refit the airlock and wait a few hours. If the smell persists, repeat the procedure. If the smell persists after four such procedures, destroy the batch.
Sour Taste: The most common cause for a sour wine is acidity. In berries (including grapes and tomatoes) and fruit, the core cause of too much acidity is most likely under-ripeness, followed by insufficient dilution with water, not enough balance with sweetness, or a combination of the foregoing with a secondary cause. Secondary causes of sourness are (a) the fruit or juice spoiled before the wine reached a self-preserving 10% alcohol level (common in watermelon), (b) a lactic acid bacterial infection soured the wine (especially likely if MLF did not conclude or sulfites were not used to prevent MLF), or (c) a souring product such as lactose (milk sugar) or lactic acid was used incorrectly. Fruit that have bruised spots (wind-fall peaches, plums, apricots, nectarines, loquats, apples, etc.) should not be used in winemaking without first cutting out the bruises, as these spots will quickly spoil and ruin the wine. Juice from melons, but especially watermelons, is prone to spoilage if fermentation is not conducted very quickly. For these wines, it is best to use a starter solution into which 2 or 3 sachets of a very fast yeast (such as Montrachet) are added to ensure a rapid build-up of yeast population before introducing it to the must. Hydrate the yeast in the starter solution for several hours before it is needed to allow the yeast population to double and redouble.
Sulfur Taste or Smell: This may occur after treatment with Campden tablets or potassium or sodium metabisulfite. It will disappear with age, but if present upon opening a bottle-aged wine, decant several hours before drinking. To prevent the preservation of sulfur taste or smell, never bottle immediately after stabilizing a wine. See Stopping Fermentation in Finishing Your Wine.
Acetification: This isn't the worse thing that can happen to wine, but it usually means the end of the wine itself. Acetification is simply the formation of vinegar. If not caught very early on, the process cannot be reversed. But at least you end up with vinegar, which is useful in itself. If ever you detect the slightest smell of vinegar and recognize an acid taste, add one crushed Campden tablet per gallon of wine and stir it in well with a sterilized rod. Wait 24 hours and restart fermentation with a fresh, vigorous yeast. If the smell of vinegar is pronounced, you cannot stop the process.
Acetification is caused by any of several the vinegar bacterium, most commonly Acetobacter aceti, Acetobacter pasteurianus and Acetobacter peroxydans. If you make homemade vinegar, commercial vinegar bacteria can easily contaminate a work area and thereafter contaminate wine if the area is not suitably cleaned after vinegar production. Wild vinegar bacteria are most often introduced on the skins of fruit used to make the wine, during primary fermentation when the must is uncovered, or by using equipment that has not been properly sterilized. It only takes one vinegar bacteria to contaminate an entire batch of wine. When using whole chopped fruit or fresh berries, flowers or leaves for winemaking, always kill off the wild microorganisms by adding one crushed Campden tablet per gallon of must, wait 24 hours, and then add your wine yeast starter. Keep the primary covered at all times except when stirring, checking specific gravity, or adding ingredients. After the initial fermentation in the secondary dies down, always keep the wine level topped up. Vinegar bacterium need air to grow, so the less air in the secondary the better. Finally, always sterilize your secondaries and racking tubes very well. At least two minutes of exposure to sterilizing solution is required to properly sterilize equipment.
Flowers of Wine: Small flecks or blooms of white powder or film may appear on the surface of the wine. If left unchecked, they grow to cover the entire surface and can grow quite thick. They are caused by spoilage yeasts and/or mycoderma bacteria, and if not caught at first appearance will certainly spoil the wine. If caused by yeast, they consume alcohol and give off carbon dioxide gas. They eventually turn the wine into colored water. The wine must be filtered at once to remove the flecks of bloom and then treated with one crushed Campden tablet per gallon of wine. The saved wine will have suffered some loss of alcohol and may need to be fortified with added alcohol (brandy works well) or consumed quickly. If caused by the mycoderma bacteria, treat the same as for a yeast infection. The Campden will probably check it, but the taste may have been ruined. Taste the wine and then decide if you want to keep it. Bacterial infections usually spoil the wine permanently, but early treatment may save it.
Prevent the introduction of spoilage yeasts and mycoderma the same way you prevent the introduction of vinegar yeasts -- by introducing early an aseptic level of sulfites.
Flowers of wine are, of course, expected when using flor sherry yeast. In such a circumstance, there is no way to know if the flowers are from the flor sherry yeast or a harmful infection. Pre-treating the must with Campden, however, should eliminate a harmful infection.
Oiliness or Ropiness: The wine develops an oily look with rope- like treads or strings appearing within it. It pours slowly and thickly with a consistency similar to egg whites, but neither its smell nor taste are effected. The culprit is a lactic acid bacterium and is only fatal to the wine if left untreated. Pour the wine into an open container with greater volume than required. Use an egg whip to beat the wine into a frothiness. Add two crushed Campden tablets per gallon of wine and stir these in with the egg whip. Cover with a sterile cloth and stir the wine every hour or so for about four hours. Return it to a sterile secondary and fit the airlock. After two days, run the wine through a wine filter and return it to another sterile secondary. Again, this problem, like most, can be prevented by pre- treating the must with Campden and sterilizing your equipment scrupulously.