Wine Faults and Flaws. Keith Grainger
the use of all chemical contact and systemic treatments well before harvesting;
Avoiding using agrochemicals that may break down into unwanted odours compounds such as 2,4‐dichlorophenol and store all agrochemicals away from possible sources of contamination;
Minimising sources of aerial pollution, including the burning of winery rubbish;
Minimising the vineyard presence of pests, particularly ladybug (Coccinellidae) and brown marmorated stink bug (Halyomorpha halys).
In the winery and cellar:
Careful oxygen management – e.g. avoiding ullage in vats and barrels and using gases to sparge equipment, but ensuring that adequate levels of dissolved oxygen are maintained;
Avoiding pick‐up of metals, particularly copper and iron – these metals can be contaminate wine from inappropriate or damaged equipment, particularly valves and fittings;
Maintaining adequate levels of molecular SO2 in wine;
Avoiding possible contact with sources of chemical contamination, e.g. damaged tank linings.
1.10.4 Physical Faults, Contamination, and Packaging Damage
Some physical faults are as a result of chemical or microbiological factors. Packaging damage or failure, sometimes due to poor storage conditions, can have devastating consequences. By way of a very simple example, a loss of bubbles (probably accompanied by oxidation) in a Champagne or other sparkling wine due to shrinkage or other failure of the cork closure would be regarded as a most serious fault. In fact a cork ‘champagne’ stopper does not provide a complete hermetic seal. Some 30% of CO2 may be lost in Champagne aged for 75 months at 12 °C (less in the case of magnum [1.5 l] bottles and more in the case of half [37.5 cl] bottles) [23]. Wine may be contaminated with a variety of objects, including flies and other insects, pieces of metal, filter materials, and oil. Whilst some of the contaminants are likely to affect bottles on an individual basis, others may require the recall of an entire batch. Occasionally pieces of glass may enter the bottle, due to problems with filling heads, the jaws of the corking or closure unit, or bottle manufacture. Wine may also become contaminated with paint, resins (including epoxy resin), brine, glycol, metals, and other substances due to damage in tanks, pipes, hoses, or other production equipment. Physical faults, physical contamination, and packaging damage are issues that affect the food, drink, and many other industries at large, and as such are not discussed in detail in this book. However, there are faults that are, or may be, related to packaging, e.g. chloroanisole contamination, that have a major organoleptic impact and these will be covered in depth.
1.11 Flaws
1.11.1 Poor Wines, as a Consequence of Adverse Weather, Sub‐standard Viticulture, Careless Winemaking, or Inappropriate Additives
Of course, there remains the question as to wines that are simply poor. A wine that is made from unripe grapes will have few attributes and may well be thin, highly acidic, lacking in fruit or varietal character and show no hints of complexity. Overripe grapes may result in a wine that is highly alcoholic, lacking in acidity, flabby, and showing baked, burnt and dried‐out tones and with reduced potential for ageing. Yet, poor as these wines may be they cannot be regarded as faulty, and it is appropriate to consider them to be flawed. In fact, any individual factor or any combination of factors that contributes to a wine being unbalanced is without doubt a flaw. The topic of ‘balance’ in wine is discussed briefly in Chapter 14. However, yet again the boundary between what is a fault or a flaw may often be soft. A wine made from grapes affected by downy mildew, commonly known as Peronospera, (taxonomic name: Plasmopara viticola), or powdery mildew, commonly known as Oïdium, (taxonomic name: Erysiphe necator [also known as Uncinula necator]), or by B. cinerea in its unwelcome form of ‘grey rot’, may result in unwanted off‐odours and off‐flavours and may be regarded as flawed, or if the off‐odours are totally unacceptable, as faulty. U. necator can impart unacceptably high levels of the compounds 1‐octen‐3‐ol and/or 1‐octen‐3‐one in wine (see Chapter 3), but fortunately most of this is enzymatically reduced during the alcoholic fermentation process. Of course, in the case of many of the world's great sweet wines both over‐ripeness and B. cinerea (in this case in the form of ‘noble rot’) are sought after, and the aroma and taste characteristics imparted as a result of the chemical changes consequential to berry infection by the fungus can send a delightful shiver down the spine. The careless or heavy‐handed use of some additives, for example, oak products in the form of powder, chips, or beans, can result in unwanted aromas, flavours, and even textural changes that can render a wine to be flawed. Wines showing a lack of typicality and, particularly in the case of protected designation of origin (PDO) wines, an absence of ‘the sense of place’, may also be regarded as flawed, although such a judgement is somewhat controversial. The 2012 vintage of ‘Les Hauts de Pontet‐Canet’, the ‘second’ wine of the flagship biodynamic Pauillac cru classé estate Château Pontet‐Canet, was denied its Appellation Controlée (AC) status by the authorities, allegedly on the grounds of lack of typicality, which led to the assessment panel considering the wine to be flawed. The owners had to accept the humble ‘Vin de France’ designation for the wine, although knowledgeable consumers were more than happy to purchase the ‘declassified’ product which, by no stretch of the imagination of anyone with an in‐depth knowledge of wine could be regarded as even slightly flawed.
1.11.2 The Presence of ‘Fault’ Compounds at Low Concentrations
The presence in wine of certain compounds at anything above trace levels, even if the concentration is below ODT or TDT, will always result in a wine a wine being faulty. TCA is a classic example. However, particularly at low concentrations, some ‘fault’ compounds may have a minor negative impact upon the nose or palate, but this may be balanced out or even outweighed by other positive attributes they exhibit or that are present in the wine, which remains eminently drinkable. The compounds metabolised by Brettanomyces yeasts are one example, and their impact at differing concentrations very much depends upon the structure and matrix of the wine.
1.12 The Incidence of Wine Faults
Should there be any illusion that wine faults are a rare occurrence, at least insofar as faulty bottles reaching the consumer is concerned, let us look at the incidence as evidenced by wines entered into a major wine tasting competition. The ‘International Wine Challenge’ is one of the world's best known annual wine tasting competitions that now attracts over 10 000 entries a year. The AWRI has reviewed wines submitted for this competition but rejected as faulty during a period of 10 years from 2007 to 2016, and quantified these as to the category of fault, and also type of closure [24]. The total number of entries reviewed was 106 627. The figures regarding faults make shocking reading. Some 3.7% of the entries were faulty. Three‐quarters of the faulty wines (2.8% of the entries) showed one of three most common faults – oxidation (1.0% of the entries), so‐called ‘cork taint’ (0.9%) and reduction/sulfides (0.9%). Alarmingly, for the lovers of aged fine wines, over 7% of the entries that were over six years old exhibited a fault, with oxidation being the most common, although excessive volatile acidity is also noted. Whilst it is obviously not possible to extrapolate these figures onto a global scale, one might estimate that, based on OIV figures for the years 2007–2018, when global wine sales annually averaged 243 million hectolitres [25], each year the equivalent of some 1.2 billion 75 cl bottles of faulty wine are sold, and presumably the vast majority of these are consumed – a particularly sobering thought!
Let us also glance at some figures for wines ascertained to be faulty wines when sent for ranking in tasting assessment features in two UK published wine magazines: ‘Decanter’ and ‘The World of Fine Wine’. As detailed in Table 1.1,