Wine Faults and Flaws. Keith Grainger

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 be uplifted by reaching for a glass of any good wine that has a story to tell.

References

      1 1 European Commission CORDIS (2016). Electronic Nose To Detect Haloanisoles In Cork Stoppers – Final Report Summary. https://cordis.europa.eu/project/rcn/111040/reporting/en (accessed October 2019).

      2 2 Schneider, V. (2010). Primer on atypical aging. Wines and Vines 4: 45–51.

      3 3 Henick–Kling, T., Gerling, C., Martinson, T. et al. (2009). Studies on the origin and sensory aspects of atypical aging in white wines. 14–16 April 2008, Trier, Germany. Proceedings of the 15th International Enology Symposium, International Association of Enology, Management and Wine Marketing, Zum Kaiserstuhl 16, 79206 Breisach, Germany.

      4 4 Hanson, A. (1982). Burgundy. London: Faber.

      5 5 Hanson, A. (1995). Burgundy, 2e. London: Faber.

      6 6 Bakker, J. and Clarke, R.J. (2012). Wine Flavour Chemistry, 2e. Chichester: Wiley–Blackwell.

1 Faults, Flaws, Off‐Flavours, Taints, and Undesirable Compounds

      In this chapter, the advances in wine technology and changes in the markets in the recent decades are discussed, along with the possible adverse impacts of some wine compounds on human health. The distinction, often made generally in the food industry, between ‘faults’ and ‘taints’ has limited validity in wines. The challenges of sensory detection thresholds of fault compounds are noted. Microbiological and chemical faults are distinguished, and the boundary between, ‘flawed’ and ‘faulty’ is discussed. At the end of the chapter, I consider whether faulty wines can be paradoxically excellent.

1.1 Introduction

      The origin of any fault or flaw in wine may be chemical, microbiological, or physical. During the process of winemaking, thousands of biochemical reactions are taking place, and most of them contribute to the aroma and flavour profile of the wine, but some are unwanted and, if not controlled or inhibited, quality will be compromised and off‐odours or faults may develop. The diverse interactions between yeasts, fungi, bacteria, and chemical compounds begin in the vineyard and continue through the production processes including maturation and even during storage after packaging. The alcohol in wine (ethanol), together with the acids, provide some stability and protection against deterioration – in fact, wine (as opposed to grape must) is a harsh environment for microbes, thereby allowing only relatively few to grow. However, some microorganisms, including unwanted yeasts and bacteria can flourish during winemaking and may remain in a wine that has finished all stages of production and cause off‐odours, off‐flavours, or product deterioration months, or even years, after bottling. Wine may become contaminated and develop such off‐odours and flavours as a result of external factors during the production processes, and even subsequent to bottling or other packaging. Common sources of contaminants include processing aids (e.g. bentonite), the winery or cellar atmosphere and environment, packaging materials (including bottle closures), and transport or storage facilities (including shipping containers).

1.2 Advances in Wine Technology in Recent Decades

The