Flaws and Faults in Wine

A significant percentage of amateur wines in competitions exhibits "off-characters". Those "off-characters" tend to be due to lack of experience in winemaking, carelessness, taking shortcuts, and also to factors beyond the winemaker's control. The presence of such wines in competitions reflects either the winemaker's inability to recognize problems in his/her wines or failure to sample each bottle submitted.

One of the greatest challenges for a wine judge is to identify the problems encountered in those wines so that constructive comments may be directed to the winemaker. It is irresponsible for a judge to write "Faulty - not marked" or "Spoiled wine - not tasted" and let it go at that. Such an approach is of no use to the winemaker. Unless a wine threatens to be so disgusting that you fear it may destroy your palate for rest of the day's judging, some attempt should be made to assess it.

You will always encounter some wines with problems you cannot identify. But if you've applied a process of elimination and still come up with an unknown, the winemaker will find it useful to know what you've ruled out. Until you become confident that you can identify a broad range of problems you may want to suggest several possible explanations. When you comment on flaws or faults, be as specific and precise as you can. Don't say "spoiled" if you know the wine has ethyl acetate, say "ethyl acetate". Don't say "off-character" if you detect acetaldehyde - be specific. Make sure the winemaker knows whether you are certain of your diagnosis or are guessing. Try to take time to include comments that can improve the competitor's winemaking. That’s your job!

Terminology of Wine Problems

First we have to establish what we mean by flaws and what we mean by faults in wine. Many wine judges use these terms interchangeably but this practice is confusing and we need to apply the terms "flaws and faults" consistently to describe the intensity and impact of problem characters as outlined below.

Almost all the off-characters we will encounter in wine can be classified as flaws when they appear in low concentrations. When they are present in even lower concentrations (usually not much higher than their threshold) some of them even add complexity to a wine, and may be considered positive attributes.

By definition, then, a flaw is character experienced as a minor departure from an acceptable norm and one that causes the wine to be atypical and less than normally enjoyable.

Judging Note: A wine with a flaw should not be scored as undrinkable on the basis of that character alone.

In comparison, a fault is a character experienced as a major departure from an acceptable norm and one that spoils the wine and causes it to be significantly atypical, usually unpleasant, and often undrinkable.

Flaws and faults fall roughly into two groups, those attributable to errors in winemaking technique or cellar management and those attributable to other factors. In the first group are errors such as incorrect sulphiting, failure to top up or check fermentation locks, failure to add nutrients, failure to rack promptly, failing to test for completion of MLF, and many more. In the second are problems over which the winemaker has less or no control such as cork quality, acetified grapes, or brett contamination.

Judging Note: It is important for judges to suggest how the winemaker can prevent or correct the detected problem in future. Faulty wines that we assess as undrinkable must be scored below 10 points. If we have had the courage to judge it despite its fault, and there's nothing wrong with its appearance (1), acid (2), sugar (1), body (1), or astringency (1), we can't give it less than 6 points. Judges who give a wine zero are reacting subjectively and perhaps trying to punish the winemaker for inflicting that entry on them. We all feel like that sometimes but we must resist that temptation.

We recommend the following approach to flawed or faulty wines. Leave unpleasant entries till after you've judged the sound(er) wines. If you can put the affected wine in your mouth, decide whether it is drinkable or undrinkable and judge it normally. Try to identify the flaw or fault without using copper. If drinkable it must be scored 10 points or higher. It is generally accepted that a wine with a flaw should not receive a medal. Then confirm or disprove the presence of reduced sulphur compounds by swirling with copper. That test should produce major improvement in nose and flavour. If there is little or no improvement consider other faults, particularly disulphides.

Clearly, a wine with very high or very low acid, inappropriate sweetness, or a wine that's currently undrinkable due to overpowering tannin, etc. is exhibiting a flaw. Judging convention assesses those characters under "Balance" and for the benefit of the winemaker their origins (usually winemaking errors) should be noted.

Table of Flaws and Faults

Common flaws or faults are listed by approximate frequency of their occurrence in flights of BCAWA wines. (Based on our experience only, subject to revision.) Percentages indicate relative frequency of flaws and faults and how much is attributable to poor winemaking practices (PW).

Name of Problem	Flaw	Fault	PW
Reduced Sulphur Compounds	20%	80%	20%
Acetaldehyde	5%	95%	100%
MLF in Bottled Wine	40%	60%	80%
Yeast Fermentation in Bottled Wine	50%	50%	100%
Ethyl Acetate	5%	95%	10%
Inadequate Settling of White Juice	80%	20%	100%
Tyrene (T.C.A.= corkiness)	20%	80%	0
2,3 ethoxy, 3,4 hexadiene (geranium)	5%	95%	90%
Candida-Acetaldehyde	0	100%	100%
Volatile Acidity – acetic acid	80%	20%	80%
Volatile Acidity – ethyl acetate	5%	95%	80%
Diacetyl	90%	10%	50%
Brettanomyces Contamination	80%	20%	0
Chemical Contaminants	0	100%	100%
Additive Overuse (SO2, Sorbate, etc)	90%	10%	100%

Other diagnosable problems may be encountered such as oxidative browning of pigments, laccase, Zygosaccharomyces deposits, ropiness, etc., but wines so-affected are very seldom entered in competitions.

Description, Cause, Prevention, Treatment, and Judging of Flaws and Faults

1. Reduced Sulphur Compounds.

a) Hydrogen Sulphide.

Description. Volatile and very potent gas (threshold is 5 parts per billion!), the gas of hot springs, redolent of rotten eggs.

Cause. Usually produced by yeast in musts that are low in nitrogen. May be related to grape variety (particularly common in Riesling, Chardonnay, and Syrah), low soil nutrients, or over-ripeness. Strongly correlated with yeast strains (e.g., D47, CY3079) that have high nutrient requirements.

Prevention. Yeasts should be rehydrated with Go-Ferm. Possibly, musts should receive an addition of diammonium phosphate within 24 hours of the start of fermentation and several more additions including Fermaid or equivalent at about 50% sugar (late in fermentation it will have little effect). Yeast strain should be selected for low H2S production. Red musts should be racked within 24 hours of pressing (even if pressed before dryness) to reduce the suspended organic material that tends to contribute to H2S formation.

Treatment. Early in fermentation add DAP if not done already. Aerate, e.g., by racking, or bubble CO2 or add Bõcksin. Persistent cases may treated with copper sulphate solution and filtration after biological activity is complete.

Judging. Easily confirmed by dropping a pre-1986 Canadian one cent piece into the glass (see Mercaptans) and swirling it for a few seconds before sniffing the greatly improved aroma. May be dissipated by covering glass with hand and shaking or may dissipate spontaneously during course of judging; in those cases it is a flaw.

b) Ethyl Mercaptan.

Description. Chemically similar to hydrogen sulphide but with one hydrogen atom replace by an alkyl group (a carbon-hydrogen chain). Less volatile than H2S. Odour very skunk-like, garlic-like, cabbage-like, sometimes fresh ground coffee, natural gas additive. Threshold about 1 part per million.

Cause. Formed after alcoholic fermentation by yeast acting on sulphur in the lees or from hydrogen sulphide.

Judging. Shaking may reduce its intensity but it usually persists. Confirmed with penny test it is a fault.

c) Thiols and Disulphides.

Description. Oxidation of ethyl mercaptan can produce diethyl disulphide with a threshold 4 ppm. Other sulphur compounds are dimethyl sulphide (25 ppm), dimethyl disulphide (29 ppm), diethyl sulphide (0.92 ppm), and ethyl sulphide (1 ppm). They have rubbery or burnt rubber odours and rubbery, soapy taste.

Judging. A sulphury, rubbery character unaffected by the penny test is probably a disulphide. Such a wine has a permanent fault.

Note: When H2S, mercaptan or disulphides are present near or perhaps slightly below their threshold of detection, no characteristic sulphury odour is present. Instead, they tend to suppress aromas that should be typical of the wine. When a wine is strangely lacking in aroma, low level sulphur compounds should be suspected. The penny test will confirm that suspicion for H2S or mercaptan. Such wines should be considered flawed.

2. Acetaldehyde

Description. Distinctive, straw-like, somewhat acrid character; sherry-like.

Cause. Since acetaldehyde becomes reduced (by alcohol dehydrogenase) to ethanol in the last step of the glycolytic pathway in fermentation it is not surprising to find that in the presence of excess oxygen, ethanol becomes oxidized back to acetaldehyde. Ullage in storage containers, empty fermentation locks, brutal racking, etc. can cause some ethanol to be oxidized to acetaldehyde.

Prevention. Minimize exposure of finished wines to air. Because of their higher phenolic content reds are less susceptible to acetaldehyde production than are whites. Maintain 25 ppm free SO2. Keep fermentation locks topped up and level of wine in storage containers topped up.

Treatment. Add 50 to 100 ppm SO2 if acetaldehyde detected. If oxidation has proceeded too far for that to be effective, treat with potassium caseinate (skim milk powder) or referment.

Judging. At barely detectable levels acetaldehyde may increase complexity but does not make a wine more enjoyable and should be considered a flaw. When readily detectable it is a fault and for most people such a wine is undrinkable. Use of the term ‘oxidation’ to denote the presence of acetaldehyde should be avoided because other wine components may also be come oxidized (e.g., phenolic browning by polyphenoloxidase).

3. MLF in Bottled Wines

Description. Musty, stale dishcloth, swampy characters that may or may not be accompanied by slight spritz. Not responsive to copper. Less objectionable in wines that have undergone MLF than in aromatic white table wines or white social wines where no MLF character might be expected.

Cause. Malolactic bacteria acting on malic acid in bottled wine. The wine was bottled with comparatively low levels and no lysozyme. Usually, the assumption has been made that MLF was completed or that since it was not deliberately added it would not occur.

Prevention. Malolactic conversion should be allowed to run its course and then be tested chromatographically to ensure no malic acid remains, or should be arrested with SO2 and then lysozyme to prevent ML bacteria starting up again in bottle. Wines that have not undergone MLF should not be blended with those that have unless lysozyme protection is used.

Judging. Depending on intensity such characters are flaws or faults and you should score the wine accordingly. There is no diagnostic test for this problem.

Note: bacterial contamination of lees can produce putrid odours and tastes reminiscent of decomposition. Prevention involves vigilant monitoring and stirring of wines "sur lie". There is no excuse for entering seriously contaminated wines in competition but if entered they are undrinkable and too unpleasant to taste.

4. Yeast Fermentation in Bottled Wine

Description. Yeasty, effervescent wine that may have stale, dirty characters. Not responsive to copper.

Cause. Wine bottled with residual sugar, viable yeast cells and inadequate SO2 or sorbate. Sugar level was assumed to be too low to ferment further or was not detected.

Judging. Wines that are clearly "working" should be scored below 10 points. Slight spritz in the absence of off-characters is acceptable in a dry white table wine or social wine.

5. Ethyl acetate.

Description. The commonest ester in wines, ethyl acetate forms from the reaction of ethanol and acetic acid. It imparts the unmistakable and usually objectionable aroma of nail-polish remover (acetone).

Cause. Ethyl acetate frequently develops in grapes on the vine from contamination with Acetobacter spp. and other aerobic bacteria converting alcohol produced by yeasts in wounds to acetic acid. It is a frequent contaminant of thin-skinned varieties of shipping grapes and of skins of grapes pressed for juice and allowed exposure to air before being used for second runs. Acetic bacteria are ubiquitous but their activity is greatly reduced by low pH, low temperature and anaerobic conditions. Sulphite is lethal to them.

Prevention. Grapes - particularly thin-skinned varieties - should be processed as soon as possible after harvest, and for second runs, crushed skins should be sprayed with sulphite solution if they can't be submerged quickly.

Treatment. Sometimes ethyl acetate will revert to the much less evident acetic acid but usually, once detected, it is very difficult to correct. Refermentation in another must will reduce it to some extent and bubbling CO2 through a sintered air-stone, then heavy PVPP fining can be effective as a last ditch measure.

Judging. A noticeable acetone character should be considered a serious fault and the wine judged as undrinkable. At almost imperceptible levels ethyl acetate may be considered a contributor to complexity, particularly in reds. Some judges are very sensitive to it and feel justified in rejecting any wine in which the slightest traces occur. (See Volatile Acidity)

6. Inadequate Settling of White Juices.

Description. A common problem in white wines is a leafy, vegetal character reminiscent of cigar butts.

Cause. Attributable to the winemaker's failure to let the juice settle adequately before fermenting. Suspended organic material is attacked by microorganisms including wild yeasts.

Prevention. Involves light (15-25 ppm) sulphiting of juice immediately after pressing; settling cold and racking settled juice off sediment before fermentation starts.

Judging. Such characters are usually considered flaws rather than faults and the wine is scored accordingly - usually not above 12 points.

7. Tyrene

Definition. Tyrene or 2,4,6 trichloro anisole (T.C.A.) is evident in both odour and flavour. It evokes the image of musty barrels, musty, dank, mouldy wood, or mouldy newpaper. Its threshold is very low - about 1.5-4 parts per billion.

Cause. Once immersed in wine, fungal spores in the lenticels of natural wine corks attack chlorine compounds that were used to bleach the cork tree bark for cosmetic purposes. T.C.A. can noticeably contaminate up to about 5% of all wines bottled under cork and produce subtle unpleasant characters in many more. T.C.A. arises infrequently in the absence of cork, sometimes from chips or barrels or winery wood treated with pentachlorophenols.

Prevention. The only reasonably certain prevention is to use artificial stoppers or Altec aggregate corks (even these may produce minor problems).

Judging. If detected, TCA should be labeled a fault. The wine is universally considered undrinkable so is scored below 10 points. Affected wines can usually be judged and since the problem is one that is difficult for the winemaker to avoid, an attempt should be made to assess the status of the wine itself.

8. Geranium character.

Cause. Malolactic bacteria acting on potassium sorbate can produce 2,3 ethoxy, 3,4 hexadiene.

Prevention. Adequate levels of sulphite when sorbate is added to prevent yeast activity in an off-dry/sweet wine act synergistically to suppress both yeast and ML activity. Wiinemakers should not attempt MLF in kits that may contain sorbate.

Judging. Even very low levels of ethoxy hexadiene are inappropriate and should be assessed as a fault and the wine considered undrinkable and scored below 10 points.

9. Candida-Acetaldehyde

Description. Wine has a distinctive, straw-like sherry-like, "dirty", acrid character;

Cause. A surface yeast, Candida vini, an obligate aerobe, may grow on the surface of wines in storage containers - particularly when ullage is too great. At the wine's surface, the combination of available oxygen, low sulphite levels and depleted alcohol provide suitable conditions. Several genera of film-forming yeasts may be involved (Pichia, Hansenula, Dekkera) and the production of acetaldehyde and other off-characters is slow and the bulk of the wine is often not affected (particularly in large containers). Films are fragile and will disintegrate easily.

Prevention. Minimize exposure of stored wines to air. Red wines are significantly more susceptible to Candida infection than are whites, perhaps simply because they tend to be handled more often and (partly as a result) may have lower levels of sulphite. Be particularly vigilant after removing samples. Monitor wines in 4-litre dark glass jugs frequently; they tend to be most vulnerable; avoid using jugs if possible. Maintain 25 ppm free SO2. Keep fermentation locks topped up and level of wine in storage containers topped up.

Treatment. Try to remove film. Add 25 to 50 ppm SO2 to render the wine less hospitable, 50 to 100 ppm if acetaldehyde detected. Spray surface with 10% sulphite solution or float pellets of metabisulphite/paraffin. If oxidation has proceeded too far, treat with potassium caseinate (skim milk powder) or referment.

Judging. At any level Candida-acetaldehyde is a fault and for most people such a wine is undrinkable and is scored below 10 points.

10. Volatile Acidity

Description. While several other volatile acids (those organic acids separable by distillation) - lactic, succinic, and propionic - occur in wine, Volatile Acidity commonly (but inaccurately) is used to refer to both acetic acid and ethyl acetate. Table vinegar is 5% (50 g/L) acetic acid whereas the threshold in wine is about 0.2 g/L. Legal limits are about 1.2 to 1.5 g/L and levels above 1.5 g/L are usually frankly vinegary. Acetic acid alone has only slight impact on aroma and bouquet but ethyl acetate is often present. The nose and particularly the flavour of acetic acid is a slightly sweet, acidic, (vinegary) character and is particularly noticeable in the aftertaste where it tends to linger.

Cause. (see Ethyl Acetate). Acetic acid bacteria (Acetobacter spp.) as contaminants of slightly fermenting damaged grapes will provide a large inoculum that can quickly produce a lot of vinegar especially in an unattended red wine cap.

Treatment. Wine with frank acetic acid should be sulphited as soon as possible to kill the bacteria. Then it can be blended with another wine and the acetic acid diluted to a level where it is not noticeable.

Judging. When ethyl acetate is present, acetic acid is difficult to detect because it is overwhelmed by the aggressiveness of the acetate ester and because few judges will actually taste such wine. When ethyl acetate is not evident, acetic acid V.A. at levels high enough to be identified is rather rare.

11. Diacetyl (2,3 butane dione)

Description. A buttery, rancid butter or butterscotch note in aroma and flavour.

Cause. A product of malolactic bacterial metabolism particularly in the absence of yeast lees which tend to neutralize the diacetyl produced. Frequently diacetyl results from the breakdown of citric acid after the malic has been consumed.

Prevention. Citric acid should not be added to wines with ML bacteria. Wines should remain 'sur lie' until MLF is completed.

Treatment. Diacetyl may be encouraged for greater butteriness. If an objectionable excess of diacetyl has formed in a wine, it may be worthwhile to store it well sulphited on another batch of clean lees.

Judging. Often an attribute, diacetyl is seldom present at levels high enough to warrant being considered more than a flaw. In reds it can be somewhat unpleasant but the wine is almost always drinkable.

If detected at levels that seem appropriate to the wine it may be considered a positive feature.

12. Brettanomyces Contamination

Description. A mousy, horsey, sweaty, wet dog, leathery, stale hamburger, barnyard character. Similar character to Belgian Lambic beer. Adds complexity at low levels.

Cause. Contamination of grapes, wines and equipment by the surface yeast, Brettanomyces spp. and its production of tetrahydropyridines.

Judging. American wine purists consider 'Brett' a fault. At low levels it not only adds complexity but may be responsible for traditional regional characters (Rhône, Burgundy). When it occurs at levels that overwhelm fruit or varietal attributes, it should be considered a flaw. 'Brett' is often associated with high pH reds because it is only volatile at neutral or high pH. Its presence can be confirmed by rubbing some wine between clean hands and sniffing the palms for the characteristic meaty note. In the mouth it is most easily detected after swallowing or spitting the wine as the oral pH returns to neutral after the more acid wine disappears.

13. Chemical Contaminants

Description. Usually unpleasant, sometimes aromatic chemical character; very uninviting.

Cause. Plastics [e.g., a green garbage bag that was used to cover a fermenter; non-food grade containers]; cellar mustiness; chlorine; detergents (more likely a contaminant of the wine glass), volatile hydrocarbons (varsol, gasoline, kerosene,etc.) stored nearby.

Judging. Their presence is a fault and renders a wine undrinkable. They fully justify not tasting the wine. Recommend winemaker discard any wine that may have been contaminated with volatiles.

14. Additive Overuse

a) High Sulphur Dioxide

Description. An acrid, tingling to burning sensation accompanied by the smell of burnt match heads or wet wool. In the mouth, a soapy character.

Cause. Prevention, Treatment. Although small amounts of SO2 are produced during fermentation, high levels are always the result of inappropriate additions by the winemaker. Intense, fresh, pungent SO2 has been recently added in excess; soapy, wet wool character indicates oversulphiting earlier.

Judging. If SO2 is noticeably pungent it should be considered a flaw and the wine marked down for its presence. Similarly, a wet wool character is a flaw, though it seems appropriate to assess it as less offensive. Recently added SO2 can be made more evident by capping glass with hand and agitating wine before sniffing it.

b). High Sorbate (2,3 hexadienoic acid)

Description. A chemical, bubblegum character to which many people are oblivious, others highly sensitive.

Cause. Use of excess potassium sorbate to prevent renewed yeast fermentation. Accepted effective dosage of sorbate is 200 mg/L (300 mg/L is BATF maximum allowed).

Judging. (Judges should be aware of their personal threshold and if they are sensitive much below the effective dosage that fact should be communicated to their judging partner when sorbate is suspected.) Wine with excess sorbate indicates poor management and it should be considered a flaw if its impact is insignificant or a fault if it overpowers the natural character of the wine. Excess sorbate is very unlikely to render a wine undrinkable.

Summary of Important Points

Usually flaws - SO2, VA., Brett, Diacetyl, Sorbate, sub-threshhold levels of reduced sulphur compounds.

Usually faults - acetaldehyde, ethyl acetate, TCA, geranium, organoleptically obvious levels of reduced sulphur compounds.

Most difficult to diagnose correctly without testing: reduced sulphur compounds and Brett.

Essential tests: improvement with penny (H2S, mercaptans); rubbing sample between hands and sniffing (Brett).

Home

Using SO2

Acid Control

Malolactic Fermentation

Postassium Sorbate

Acid & pH Adjustment

Hydrogen Sulfide

Care of Corks

Fining and Fining Agents

Why pH & TA are not proportional

SO2 Measurement Tables

pH Without Pain

Grape Varieties and Blending

Words to describe wine

Winemaking Log

Wine Scoring Card