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An article for competition wine judges and
of interest to competitors
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).
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
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.
Prevention and Treatment. See 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.
Cause. Usually, conversion from ethyl mercaptan.
Treatment. Cannot be removed by aeration or
copper sulphate treatment.
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.
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).
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.
Treatment. No practical solution.
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.
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.
Treatment. Disgorge and referment entire
bottling.
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.
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)
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.
Treatment. No practical solution.
Judging. Such characters are usually considered
flaws rather than faults and the wine is scored accordingly - usually not
above 12 points.
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).
Treatment. None.
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.
Description. A strong resemblance to geranium
leaves in aroma and flavour.
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.
Treatment. None known.
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.
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.
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.
Prevention. See ethyl acetate.
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.
Prevention. Regular rinsing of equipment and
attention to sulphite levels.
Treatment. Unknown
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.
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.
Prevention is obvious.
Treatment. No practical solution.
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.
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).
Prevention. Careful weighing of sorbate.
Treatment. None known.
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
Flaw: minor departure from acceptable norm.
Wine usually drinkable.
Usually flaws - SO2, VA., Brett, Diacetyl,
Sorbate, sub-threshhold levels of reduced sulphur compounds.
Fault: major departure from acceptable norm.
Wines usually undrinkable.
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).
George Gibson
Mike Farkas Also see: ETS
Laboratories
Sulfides in wine |