In winemaking, either fruit or grape, we always want to make and drink a good wine. In a perfect world, that is the case (and the wine is free and ever flowing ;-).
However, we unfortunately do not live in a perfect world and being able to learn from mistakes we make along the way is all part of the game. The goal is to make less and less mistakes, learn from them and in the end use the experience we have gained to make a flawless wine that will wine top prize in a competition and make all who drink it recite poems of love and extacy (ok, I may be going a little far here but you catch my drift).
The following few blog entries will cover different aspects of “wine problems” and hopefully help you identify them before they get to the point of no return…
A lot of wines, especially at the amateur winemaking level can 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 can reflects either the winemaker’s inability to recognize problems in his/her wines.
One of the greatest challenges for a winemaker or a wine judge is to identify the problems encountered in those wines. Unless a wine threatens to be so disgusting that you fear it may destroy your palate, some attempt should be made to assess it and find a way to prevent this kind of problem from happening again.
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, at least you will find it useful to know what you’ve ruled out.
Terminology of Wine Problems
First we have to establish what we mean by flaws and what we mean by faults in wine. Many winemakers 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.
Almost all the off-characters we 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.
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.
The following list of pretty much all possible wine problems should be a very helpful guide to all winemakers.
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 copper 1-cent piece (Canadian or USA) 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 above.
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. sorry 🙁
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
Come back in a few days for more on this important winemaking topic. Let me know what you think maybe share some of your own winemaking experience with wine problems. Sharing our information will help make a world with better wine! I think we can all drink to that.