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 and microbiologically and be declared technically very good and free from flaws, yet may taste distinctly uninteresting. Another may show technical weaknesses or even flaws, yet when tasted, it can be so full of character and true to its origin that it sends a shiver down the spine, and must be regarded as of the very highest quality. Returning briefly to the topic of Brettanomyces, Château de Beaucastel, a Châteauneuf‐du‐Pape from France's southern Rhône valley, and Chateau Musar from the Bekar valley in Lebanon are two examples of brilliant, distinctive, and exhilarating wines that historically showed considerable ‘Brett’ characteristics. Many lovers of these wines are still nurturing their mature stocks, as recent vintages have been much tamer. Such characteristics are not to everybody's palate, but using analogies from the music and art worlds, a person who loves Puccini is perhaps not that fond of the works of Ed Sheeran, and somebody overwhelmed by Titian may be distinctly unmoved by Paul Klee.
Perceptions of faults and flaws are subject to the sensitivity of individual tasters, and humans vary considerably in their sensory detection thresholds and their reactions to individual taints. For most of the faults discussed in this book, detection thresholds (in wine) are stated. These sometimes split into odour detection and taste detection thresholds when researchers have quantified such information. The figures stated are not always straightforward or beyond dispute. Sensory perception thresholds are usually different for red, rosé, white, sparkling, and fortified wines. Further, the level at which a compound that may constitute a fault becomes apparent may vary according to the wine matrix, which includes grape variety or varieties, style, alcoholic content, structure and balance, and is not simply a matter of quantification of the compounds responsible. The topics of sensory perceptions, detection thresholds and consumer rejection thresholds are discussed generally in Chapters 1 and 2, and also in Chapters 3–15 that cover individual faults.
The final, and most important, dichotomy briefly considered in this Introduction is that of two contrasting and perhaps incompatible approaches to wine production: (i) ‘minimum intervention’ and (ii) ‘technical excellence’. ‘Great wine is made in the vineyard’ is an oft heard expression, used in equal abundance by quality‐conscious producers, critics, and serious wine lovers. In other words, if the harvested crop is of the highest quality and bears the hallmarks of a distinguished area of production, the art and science of turning this into top‐quality wine is not that hard. Conversely, no amount of intervention or high‐tech equipment can make a superb wine from fruit that is unripe, diseased, over‐cropped or otherwise undistinguished, grown on unsuitable soils, or in adverse weather or climatic conditions. When studying the classic works on oenology and numerous research papers, it is easy to be led to believe that winemaking is all about the use of cultured yeast strains, enzymes, fining agents, sterile filtration, reverse‐osmosis (RO) machines, and a thousand and one vehicles of intervention. When talking to many producers of great wines that have a sense of place, with a unique identity, a very different picture is painted, and we find that with the occasional exception of certain fining agents, many do not employ any of the above. Care, time, and ‘listening to the wine’ are seen as the pathways to producing distinctive wines, and any additive or cellar operation that might compromise individuality is forsaken. Indeed, numerous producers who make exhilarating wines will challenge the use of some of the methods and the necessity for the oenological products, detailed in the sections of this book where prevention of individual faults are discussed.
Whilst this book has been designed to be readable from cover to cover, each chapter is also written as a stand‐alone so that the reader seeking information on a specific topic can find the required material in one place. On occasions, there is repetition as the steps to be taken to prevent an individual fault may be very similar to those undertaken to avoid others, and matters of good winery hygiene are central to producing wines free of fault or taint. To maximise readability and avoid confusion between similar sounding organisms or chemical compounds, I sometimes break from conventions used in works that are designed for academic and scientific readers, such as using only the initial of a genus after its first appearance in a chapter, and only using acronyms after the abbreviated word or phrase has been detailed.
Writing a book such as this presents numerous challenges, and it has also changed the way I assess wine, even impacting upon enjoyment. As my wife Paula said to me, ‘You have stopped listening to the music and started listening to the sound‐system’. I hope that readers are not affected in the same way. But as our journey proceeds through the wide territory of wine faults and flaws, and although we may find some of the ‘terroir’ hostile, there are also interesting vinous discoveries to be made. From time to time, we may wander down side roads, but never blind alleys. When walking any city street, we must look up and down, as well as from side to side – faults and flaws are all part of a greater picture and are relative to their surroundings. And if on occasions, we find our journey to be a little dry, we can always
