all wine producing countries’ [2]. It has been estimated that up to 20% of USA wines might be affected [3].
The financial impact upon producers and distributors who have sold faulty product can be immediate and direct. Supermarkets and merchants impose chargebacks upon suppliers when customers return wines. On an individual basis, this may be the cost of the bottle in question, the cost of analysis of other bottles, the cost of replacement bottles and a ‘fine’, or service handling fee. On a volume basis, the trade customer may demand reimbursement for pallets or even containers of affected wine, shipping and warehouse costs, handling, and possibly also excise duties which, in some countries, can amount to several times the value of the wine in question. If there are problems with subsequent shipments, the merchant may well blacklist the producer or supplier. The longer‐term financial impact can be massive. For example, winery contamination with haloanisoles has, on occasions, necessitated the destruction and rebuilding of cuveries and chais, as discussed in Chapter 3.
In Chapters 3–14, I discuss in detail individual categories of wine faults. I do not claim the list of faults included to be exhaustive. The discussion of each fault generally includes:
What it is, in basic terms;
How it can be detected by:sensory recognition, including sensory detection thresholds;laboratory analysis;
What the cause is;
At which stage/s of production, maturation, or storage it can occur;
How it might be prevented;
Whether an affected wine is treatable, and if so how;
The detailed science applicable to the fault.
The ‘history’ of the individual faults is also covered. Throughout the book, particularly Chapter 18, there is a general discussion of the implementation of what constitutes good procedures and practices in the vineyard and winery to enhance quality and minimise the likelihood of faults from occurring. Carrying out audits of premises, equipment, and inventory to identify microbial or chemical contamination can be costly and taking steps to address issues identified even more so. The cost of being unaware of problems, or doing nothing to rectify them, is incalculable. I am acutely aware of budget constraints that are an everyday challenge, particularly to the small producer, and such implementation may be generally achieved at minimum expense. Information on the identification of faults by laboratory analysis, and how faults may be rectified is given in general terms. However, producers seeking to address specific issues are advised to seek advice from any of the laboratories, consultants, and companies specialising in the identification and treatment of oenological problems. It is the responsibility of producers to check the legality of any method suggested, or the addition of any oenological products, in the country/region of production and market.
There are several challenges posed in undertaking any discussion of wine faults and flaws. These include matters of definitions, boundaries, concentrations, and the matrices of individual wines. From a sensory perspective, determining when a microbial or chemical issue is a fault is not necessarily straightforward. In addition to the issue of a taster's sensory detection thresholds, there can often be a dispute whether a particular characteristic is perceived as beneficial, harmless, a flaw or a fault. These perceptions are even subject to the vagaries of fashion. In 1982, Master of Wine and Burgundy expert Anthony Hanson wrote in the first edition of his critically acclaimed book Burgundy: ‘great Burgundy smells of shit’ [4]. If there were any raised eyebrows at the time, these were only because of Hanson's choice of language.
Indeed many Burgundies exuded the odours of stables and farmyards. By 1995, Hanson was already finding such a nose objectionable and blamed microbial activity [5]. We now know that these odours have nothing to do with Pinot Noir (the variety from which pretty much all red Burgundy is made). Nor do they stem from any of the myriads of Burgundy terroirs, but result from volatile phenols and other compounds produced by the yeast Brettanomyces (or to be technically correct Dekkera although it is rarely so‐called in the wine industry). Today, Brettanomyces is generally regarded in the wine industry as a rogue yeast, and odours of farmyards, stables, or BAND‐AID® are generally considered to be undesirable and regarded by most winemakers, oenologists, and critics to be a fault. This means that aromas in 1982 regarded by an expert taster as a sign of quality are today usually seen as a fault. However, Brettanomyces (often referred to as ‘Brett’) remains a controversial topic. Many producers, critics, and wine lovers believe it can, at low levels, add complexity to a wine. This poses the question as to where the boundary should be drawn. Purists perceive Brett always to be a fault and define it as such. Some lovers of ‘natural’ wines consider it to be one of nature's distinctive aroma and flavour giving yeasts. In some countries, the number of wines showing Brett characteristics is increasing, due in part to winemakers trying to satisfy perceived consumer demands. As Jokkie Bakker and Ronald J. Clarke note, ‘changes in winemaking culture as a result of changes in consumer preference for the required style of wine has led to an increase in some off‐flavour formation, for example volatile ethyl phenols (which are by metabolised by Brettanomyces) [6]’. I examine the topic of Brettanomyces and related volatile phenols, in Chapter 4.
We may draw another example of definition/boundary/concentration challenges when discussing volatile sulfur compounds, which can be a consequence of agronomic conditions or reductive winemaking techniques. Some of these compounds may, at modest concentrations, give notes of minerality, a hint of struck match, ‘gun‐flint’, and of savoury ‘lamb fat’. Such characteristics may be considered positive in, for example, white Burgundies and the white wines of the Central Vineyards of the Loire Valley. However, at high levels, volatile sulfur compounds can give most undesirable odours, including bad eggs, onion, garlic, skunk, town gas, and faeces. But at just what point is the desirable concentration exceeded? A risqué comedian may be very funny until a boundary is crossed, beyond which they are perceived to be obscene.
A further illustration of these boundary challenges may be made when discussing excessive volatile acidity (VA). Many Italian red wines have high levels of VA, which in wines from other countries might be considered to be at very least a flaw, but which contributes to the ‘Italian’ character of the wines. Whilst a high level of VA in the red wines of Bordeaux is not acceptable today, times and palates change. The 1947 vintage of Château Cheval Blanc, Saint–Émilion, made before the advent of temperature controlled fermentations and described by some critics as the greatest wine of all time, possesses such high VA that by today's thinking it would be perceived as not just flawed, but seriously faulty. The topic of excessive VA is discussed in Chapter 7.
The final example of these challenges in this Introduction relates particularly to mature Riesling wines. Many producers in Germany and Alsace have long lauded the diesel or kerosene nose that examples can exhibit after several years in the bottle. Most New World producers and wine critics regard such a nose as indicative of a flaw at least, caused by 1,1,6‐trimethyl‐1,2‐dihydronaphthalene (TDN), a norisoprenoid. At other than very low concentrations, they consider the wine to be faulty. In common with many other European‐based wine writers and authors, I disagree with the defining TDN as a flaw or fault, unless the level is overwhelming (another boundary challenge). The aroma characteristics imparted by TDN can add exhilarating notes that in wines from some regions form part of the individual, sensuous character of this most distinctive of varieties. This topic is discussed in Chapter 15. Bearing in mind that sensory characteristics change according to when in a wine's life‐cycle it is assessed, and using the examples I have given, a particular compound and resulting odour or taste may be considered to comprise a fault or flaw, when in the wrong concentration, in the wrong wine, in the wrong place, and at the wrong time!
There are apparent contradictions in how we assess and define wine quality. One wine can be analysed chemically