Wine fault
A wine fault is a sensory-associated (
In the case of a chemical origin, many compounds causing wine faults are already naturally present in wine, but at insufficient concentrations to be of issue, and in fact may impart positive characters to the wine; however, when the concentration of such compounds exceed a
There are many underlying causes of wine faults, including poor
Differences between flaws and faults
In wine tasting, there is a big distinction made between what is considered a flaw and a fault. Wine flaws are minor attributes that depart from what are perceived as normal wine characteristics. These include excessive
Detecting faults in wine tasting
The vast majority of wine faults are detected by the nose and the distinctive aromas that they give off. However, the presence of some wine faults can be detected by visual and taste perceptions. For example, premature oxidation can be noticed by the yellowing and
Wine fault | Characteristics |
Acetaldehyde | Smell of roasted nuts or dried out straw. Often described as green apples and emulsion paint. Commonly associated with Sherries where these aromas are considered acceptable |
Amyl-acetate |
Smell of "fake" candy banana flavoring |
Brettanomyces | Smell of barnyards, fecal and gamey horse aromas |
Cork taint | Smell of a damp basement, wet cardboard or newspapers and mushrooms |
Butyric acid | Smell of rancid butter |
Ethyl acetate | Smell of vinegar, paint thinner and nail polish remover |
Hydrogen sulfide | Smell of rotten eggs or garlic that has gone bad |
Iodine | Smell of moldy grapes |
Lactic acid bacteria | Smell of sauerkraut |
Mercaptans |
Smell of burnt garlic or onion |
Oxidation |
Smell of cooked fruit and walnuts. Also detectable visually by premature browning or yellowing of the wine |
Sorbic acid plus lactic acid bacteria | Smell of crushed geranium leaves |
Sulfur dioxide | Smell of burnt matches. Can also come across as a pricking sensation in the nose. |
Oxidation
The
Acetaldehyde
Acetic acid
There are different opinions as to what level of volatile acidity is appropriate for higher quality wine. Although too high a concentration is sure to leave an undesirable, 'vinegar' tasting wine, some wine's acetic acid levels are developed to create a more 'complex', desirable taste.[7] The renowned 1947 Cheval Blanc is widely recognized to contain high levels of volatile acidity.
Sulfur compounds
Sulfur is used as an additive throughout the winemaking process, primarily to stop oxidation as mentioned above but also as antimicrobial agent. When managed properly in wine, its presence there is often undetected, however when used recklessly it can contribute to flavour and aroma taints which are very volatile and potent. Sulfur compounds typically have low sensory thresholds.
Sulfur dioxide
Sulfur dioxide is a common wine additive, used for its antioxidant and preservative properties. When its use is not managed well it can be overadded, with its perception in wine reminiscent of matchsticks, burnt rubber, or mothballs. Wines such as these are often termed sulfitic.
Hydrogen sulfide
Hydrogen sulfide (H2S) is generally thought to be a metabolic by-product of yeast fermentation in nitrogen limited environments. It is formed when yeast ferments via the sulfate reduction pathway. Fermenting wine is often supplemented with diammonium phosphate (DAP) as a nitrogen source to prevent H2S formation. The sensory threshold for hydrogen sulfide is 8-10 μg/L, with levels above this imparting a distinct rotten egg aroma to the wine. Hydrogen sulfide can further react with wine compounds to form mercaptans and disulfides.
Mercaptans
with levels above causing onion, rubber, and skunk type odours. Note that dimethyl disulfide is formed from the oxidation of methyl mercaptan.Dimethyl sulfide
Dimethyl sulfide (DMS) is naturally present in most wines, probably from the breakdown of sulfur containing amino acids. Like ethyl acetate, levels of DMS below the sensory threshold can have a positive effect on flavour, contributing to fruityness, fullness, and complexity. Levels above the sensory threshold of >30 μg/L in white wines and >50 μg/L for red wines, give the wine characteristics of cooked cabbage, canned corn, asparagus or truffles.
Environmental
Cork taint
Cork taint is a wine fault mostly attributed to the compound
Heat damage
Heat damaged wines are often casually referred to as cooked, which suggests how heat can affect a wine. They are also known as maderized wine, from Madeira wine, which is intentionally exposed to heat. The ideal storage temperature for wine is generally accepted to be 13 °C (55 °F). Wines that are stored at temperatures greatly higher than this will experience an increased aging rate. Wines exposed to extreme temperatures will thermally expand, and may even push up between the cork and bottle and leak from the top. When opening a bottle of wine, if a trace of wine is visible along the length of the cork, the cork is partially pushed out of the bottle, or wine is visible on the top of the cork while it is still in the bottle, it has most likely been heat damaged. Heat damaged wines often become oxidized, and red wines may take on a brick color.
Even if the temperatures do not reach extremes, temperature variation alone can also damage bottled wine through oxidation. All corks allow some leakage of air (hence old wines become increasingly oxidized), and temperature fluctuations will vary the pressure differential between the inside and outside of the bottle and will act to "pump" air into the bottle at a faster rate than will occur at any temperature strictly maintained.
Reputedly, heat damage is the most widespread and common problem found in wines. It often goes unnoticed because of the prevalence of the problem, consumers don't know it's possible, and most often would just chalk the problem up to poor quality, or other factors.
Lightstrike
Lightstruck wines are those that have had excessive exposure to
Ladybird (pyrazine) taint
Some insects present in the grapes at harvest inevitably end up in the press and for the most part are inoffensive. Others, notably the
Microbiological
Brettanomyces (Dekkera)
The yeast Brettanomyces produces an array of metabolites when growing in wine, some of which are volatile phenolic compounds. Together these compounds are often referred to as phenolic taint, "Brettanomyces character", or simply "Brett". The main constituents are listed below, with their sensory threshold and common sensory descriptors:
- 4-ethylphenol(>140 μg/L): Band-aids, barnyard, horse stable, antiseptic
- 4-ethylguaiacol(>600 μg/L): Bacon, spice, cloves, smoky
- isovaleric acid: Sweaty, cheese, rancidity
Geosmin
Lactic acid bacteria
Lactic acid bacteria have a useful role in winemaking converting malic acid to lactic acid in malolactic fermentation. However, after this function has completed, the bacteria may still be present within the wine, where they can metabolise other compounds and produce wine faults. Wines that have not undergone malolactic fermentation may be contaminated with lactic acid bacteria, leading to refermentation of the wine with it becoming turbid, swampy, and slightly effervescent or spritzy. This can be avoided by sterile filtering wine directly before bottling. Lactic acid bacteria can also be responsible for other wine faults such as those below.
Bitterness taint
Bitterness taint or amertume is rather uncommon and is produced by certain strains of bacteria from the genera Pediococcus, Lactobacillus, and Oenococcus. It begins by the degradation of glycerol, a compound naturally found in wine at levels of 5-8 g/L, via a dehydratase enzyme to 3-hydroxypropionaldehyde. During ageing this is further dehydrated to acrolein which reacts with the anthocyanins and other phenols present within the wine to form the taint.[12] As red wines contain high levels of anthocyanins they are generally more susceptible.
Diacetyl
Diacetyl in wine is produced by lactic acid bacteria, mainly Oenococcus oeni. In low levels it can impart positive nutty or caramel characters, however at levels above 5 mg/L it creates an intense buttery or butterscotch flavour, where it is perceived as a flaw. The sensory threshold for the compound can vary depending on the levels of certain wine components, such as sulfur dioxide. It can be produced as a metabolite of citric acid when all of the malic acid has been consumed. Diacetyl rarely taints wine to levels where it becomes undrinkable.[13]
Geranium taint
Geranium taint, as the name suggests, is a flavour and aroma taint in wine reminiscent of
Mannitol
Ropiness
Ropiness is manifested as an increase in viscosity and a slimey or fatty mouthfeel of a wine. In France the fault is known as "graisse", which translates to fat. The problem stems from the production of dextrins and polysaccharides by certain lactic acid bacteria, particularly of the genera Leuconostoc and Pediococcus.
Mousiness
Mousiness is a wine fault most often attributed to Brettanomyces but can also originate from the
- 2-acetyl-3,4,5,6-tetrahydropyridine
- 2-acetyl-1,4,5,6-tetrahydropyridine
- 2-ethyltetrahydropyridine[15]
- 2-acetyl-1-pyrrolene
The taints are not volatile at the pH of wine, and therefore not obvious as an aroma. However, when mixed with the slightly basic pH of saliva they can become very apparent on the palate,[16] especially at the back of the mouth, as mouse cage or mouse urine.
Refermentation
Refermentation, sometimes called
Bunch rots
Organisms responsible for bunch rot of grape berries are filamentous fungi, the most common of these being
See also
References
- ^ Merriam-Webster. (n.d.). Organoleptic. In Merriam-Webster.com dictionary. Retrieved June 26, 2023, from https://www.merriam-webster.com/dictionary/organoleptic.
- ^ Watrelot, Aude; Savits, Jennie & Moroney, Maureen (2020). "Wine Fault Series" (PDF). ISU Extension and Outreach (Extension.IAState.edu). Ames, IA: Iowa State University (ISU). Retrieved June 26, 2023.
This summary document lists the common wine faults including the name of the fault, the type of the fault, the odor characteristics, and the chemical responsible. A wine fault is an unpleasant organoleptic characteristic including look, smell, or taste. Wine faults can come from a chemical or a microbial origin and some off-odors can be the result of multiple faults.
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: CS1 maint: multiple names: authors list (link) - ^ ]
- ^ ]
- ^ duToit, W.J. (2005). Oxygen in winemaking: Part I. WineLand, accessed on 2 April 2006.
- ^ Goode, Jamie (06/25/19). Oxidation in wine Archived 2021-02-10 at the Wayback Machine. internationalwinechallenge.com, accessed on 10 February 2021.
- ^ Volatile Acidity - article from Wine & Spirit magazine.
- ^ Technical Bulletin - Sulfides in Wine Archived 2007-12-11 at the Wayback Machine. etslabs.com, accessed on 12 March 2006.
- ^ LaMar, Jim (09/25/02). Cork Taint, accessed on 12 March 2006.
- ^ Drouhin, R.J. (01/23/98) Bottle Glass Archived 2007-12-11 at the Wayback Machine, accessed 3 April 2006.
- ^ Kennel, Florence (14/12/05). Bordeaux boffin solves geosmin conundrum. Decanter.com, accessed on 2 April 2006.
- ^ a b c d duToit, M., Pretorius, I.S. (2000). "Microbial spoilage and preservation of wine: Using weapons from nature's own arsenal - A review". South African Journal of Enology and Viticulture 21: 74-96.
- ^ Gibson, George; Farkas, Mike Flaws and Faults in Wine, accessed on 12 March 2006.
- ^ "Wine Faults, Flavours, and Taints". The Australian Wine Research Institute. Retrieved August 21, 2021.
- ^ Marais, Johann Flavourful nitrogen containing wine constituents Archived 2006-09-28 at the Wayback Machine. Wynboer.co.za, accessed on 12 March 2006.
- ^ Gawell, Richard Somellier, A Mouse Must Have Wee'd in My Wine!. aromadictionary.com, accessed on 12 March 2006.
- .
External links
- Organoleptic defects in wine (PDFdocument) Link Not Working
- How to Spot Faulty Wine, from The Wine Doctor Link Not Working
- [1] in Enobytes Wine Online