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- Herausgeber: John Wiley & Sons
- Kategorie: Lebensstil
- Sprache: Englisch
2022 Winner of the OIV Award in the Oenology category An essential guide to the faults and flaws that can affect wine Written by the award-winning wine expert, Keith Grainger, this book provides a detailed examination and explanation of the causes and impact of the faults, flaws and taints that may affect wine. Each fault is discussed using the following criteria: what it is; how it can be detected by sensory or laboratory analysis; what the cause is; how it might be prevented; whether an affected wine is treatable, and if so, how; and the science applicable to the fault. The incidences of faulty wines reaching the consumer are greater than would be regarded as acceptable in most other industries. It is claimed that occurrences are less common today than in recent recorded history, and it is true that the frequency of some faults and taints being encountered in bottle has declined in the last decade or two. However, incidences of certain faults and taints have increased, and issues that were once unheard of now affect many wines offered for sale. These include 'reduced' aromas, premature oxidation, atypical ageing and, very much on the rise, smoke taint. This book will prove invaluable to winemakers, wine technologists and quality control professionals. Wine critics, writers, educators and sommeliers will also find the topics highly relevant. The wine-loving consumer, including wine collectors will also find the book a great resource and the basis for discussion at tastings with like-minded associates. Reviews I read this book avidly from cover to cover. I'll dip into it for future reference as required, which is how many will employ it. Meanwhile, I learned a great deal, and it now influences how I think about wine evaluation. I commend this excellent new book to you. Consider it an investment. Paul Howard, Wine Alchemy
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Table of Contents
Cover
Title Page
Copyright
Dedication
Acknowledgements
Preface
Introduction
References
1 Faults, Flaws, Off‐Flavours, Taints, and Undesirable Compounds
1.1 Introduction
1.2 Advances in Wine Technology in Recent Decades
1.3 Changes in Markets and the Pattern of Wine Consumption in Recent Decades
1.4 The Possible Impact of Some Fault Compounds Upon Human Health
1.5 Sulfur Dioxide and Other Possible Allergens
1.6 Faults and Taints
1.7 Distinguishing Between Faults and Flaws
1.8 Sensory Detection (Perception) Thresholds and Sensory Recognition Thresholds
1.9 Consumer Rejection Thresholds (CRTs)
1.10 Basic Categories of Wine Faults
1.11 Flaws
1.12 The Incidence of Wine Faults
1.13 ‘Faulty’ Wines that Exude Excellence
1.14 Final Reflections
References
2 Wine Tasting
2.1 Introduction
2.2 Anosimics, Fatigue Effect, and Supertasters
2.3 Tasting Conditions, Equipment, and Glassware
2.4 The Use of a Structured Tasting Technique and Detection of Faults
2.5 Appearance
2.6 Nose
2.7 Palate
2.8 Assessment of Quality
2.9 Assessment of Readiness for Drinking/Potential for Ageing
2.10 Grading Wine – The Award of Points
2.11 Blind Tasting
2.12 Final Reflections
References
3 Chloroanisoles, Bromoanisoles, and Halophenols
3.1 Introduction
3.2 Haloanisole Contaminations in the Food, Drinks, Water, and Pharmaceutical Industries
3.3 Haloanisole Contamination of Wines
3.4 The Economic and Reputational Costs to Wine Producers and the Wine Industry
3.5 Sensory Characteristics and Detection of Haloanisoles in Wine
3.6 The Haloanisoles Responsible and Their Detection Thresholds
3.7 The Formation Pathways of Haloanisoles from Halophenols
3.8 Contamination of Cork with TCA and Other Chloroanisoles
3.9 The Cork Industry in the Dock
3.10 The Cork Industry Begins to Address the Issues
3.11 The Cork Industry's Recent Initiatives for Haloanisole Prevention and Extraction
3.12 Winery and Cooperage Sources of Haloanisole Contamination in Wines
3.13 Laboratory Analysis for TCA and Other Haloanisoles in Corks and Wine
3.14 Prevention of Haloanisole Contamination of Wineries and Wines
3.15 Treatment of Wines Contaminated with Haloanisoles
3.16 Chlorophenols and Bromophenols as Taints
3.17 ‘Musty’ Taints Unrelated to Halophenols and Haloanisoles
3.18 Final Reflections
References
4
Brettanomyces (Dekkera)
and Ethyl Phenols
4.1 Introduction
4.2 Background and History
4.3 The Brett Controversy
4.4 Sensory Characteristics and Detection of Brettanomyces‐Related Compounds in Wine
4.5 The Origins of Brettanomyces and Formation of Related Compounds in Wines
4.6 The Danger Periods and Favourable Conditions for the Growth of Brettanomyces
4.7 Why Are Brettanomyces‐Related Compounds Found Mostly in Red Wines?
4.8 Prevention: Formulation and Implementation a Brett Control Strategy
4.9 Laboratory Analysis for Brettanomyces and Volatile Phenols
4.10 Treatment of Affected Wines
4.11 What the Future Might Hold for Microbiological Methods to Inhibit Brettanomyces?
4.12 Final Reflections
References
5 Oxidation, Premox, and Excessive Acetaldehyde
5.1 Introduction
5.2 Oxidation in Must and Wine
5.3 Sensory Characteristics and Detection of Excess Acetaldehyde and Oxidation in Wine
5.4 Deliberately Oxidised and Highly Oxygenated Wines
5.5 Metal Ions and Substrates for Oxidation
5.6 Enzymatic Oxidation
5.7 Chemical Oxidation
5.8 Microbial Oxidation
5.9 Acetaldehyde
5.10 Sotolon
5.11 Oxygen Management in Winemaking
5.12 Oxygen Uptake During Cellar Operations
5.13 Containers and Closures
5.14 Pinking
5.15 Premature Oxidation (Premox)
5.16 Prevention of Excess Acetaldehyde and Oxidation
5.17 Additions of Ascorbic Acid: Antioxidant or Oxidising Agent?
5.18 Laboratory Analysis
5.19 Treatments
5.20 Final Reflections
References
6 Excessive Sulfur Dioxide, Volatile Sulfur Compounds, and Reduced Aromas
6.1 Introduction
6.2 The Presence and Role of Sulfur, Sulfur Dioxide, Sulfite, and Sulfate in Wine Production
6.3 Excessive Sulfur Dioxide
6.4 Oxygen Management in Winemaking
6.5 Reduction in Wine: Positive and Negative
6.6 Hydrogen Sulfide
6.7 Prevention of Hydrogen Sulfide Formation
6.8 Treatment for Hydrogen Sulfide in Wine
6.9 Mercaptans, Sulfides, Disulfides, Trisulfides, and Thioesters
6.10 Post‐bottling Reduction
6.11 Lightstrike
6.12 Laboratory Analysis for Sulfur Dioxide, Hydrogen Sulfide, and Volatile Sulfur Compounds
6.13 Final Reflections
References
7 Excessive Volatile Acidity and Ethyl Acetate
7.1 Introduction
7.2 Volatile Acidity and Ethyl Acetate
7.3 The Controversy of High Levels of Volatile Acidity
7.4 Fixed Acids and Volatile Acids
7.5 Sensory Characteristics and Detection of Volatile Acidity
7.6 Legal Limits
7.7 Acetic Acid Bacteria
7.8 Production of Acetic Acid in Wine
7.9 Ethyl Acetate
7.10 Prevention of Excessive Volatile Acidity and Ethyl Acetate
7.11 Laboratory Analysis
7.12 Treatments
7.13 Final Reflections
References
8 Atypical Ageing (ATA) – Sometimes Called Untypical Ageing (UTA)
8.1 Introduction
8.2 The Atypical Ageing Controversy
8.3 The Causes of Atypical Ageing and Formation Pathways
8.4 Sensory Detection
8.5 Laboratory Detection
8.6 The Main Viticultural Causes of ATA
8.7 Prevention
8.8 Treatments
8.9 Final Reflections
References
9 Fermentation in Bottle
9.1 Introduction
9.2 Sensory Detection
9.3 Alcoholic Fermentation in Bottle
9.4 Malolactic Fermentation (MLF) in Bottle
9.5 Prevention: Preparing Wine for Bottling and the Bottling Process
9.6 Treatment
9.7 Final Reflections
References
10 Hazes
10.1 Introduction
10.2 Protein Haze
10.3 Microbial Hazes
10.4 Metal Hazes
10.5 Final Reflections
References
11 Lactic Acid Bacteria‐Related Faults
11.1 Introduction to Lactic Acid Bacteria
11.2 Lactic Acid Bacteria and Their Natural Sources
11.3 Malolactic Fermentation (MLF)
11.4 Undesirable Aromas, Off‐Flavours, and Wine Spoilage Caused by Lactic Acid Bacteria
11.5 Prevention of Lactic Acid Bacteria‐Related Faults
11.6 Analysis
11.7 Final Reflections
References
12 Smoke Taint and Other Airborne Contaminations
12.1 Introduction
12.2 Smoke Taint Compounds in the Atmosphere
12.3 Critical Times in the Growing Season and Duration of Exposure for Smoke Taint to Impact
12.4 The Volatile Phenols Responsible for Smoke Taint; Their Odours and Flavours and Sensory Detection Thresholds
12.5 Smoke Taint in Wines
12.6 Other Sources of Guaiacol and 4‐Methyl‐guaiacol in Wines
12.7 Laboratory Testing
12.8 Prevention of Development of Smoke‐Related Volatile Phenols from Affected Grapes
12.9 Treatments
12.10 Other Airborne Contaminations
12.11 Final Reflections
References
13 Ladybeetle and Brown Marmorated Stink Bug Taints
13.1 Introduction
13.2 Methoxypyrazines
13.3 Ladybeetles (Also Known as Ladybirds and Ladybugs)
13.4 Brown Marmorated Stink Bug (
Halyomorpha halys
) Taint
13.5 Final Reflections
References
14 Sundry Faults, Contaminants, Including Undesirable Compounds from a Health Perspective and Flaws Due to Poor Balance
14.1 Mycotoxins, Particularly Ochratoxin A
14.2 Dibutyl Phthalate and Other Phthalates
14.3 Ethyl Carbamate
14.4 Biogenic Amines
14.5 Ethyl Sorbate and Sorbyl Alcohol (Geraniol) Off‐Odours
14.6 Paper‐Taste
14.7 Plastic Taints – Styrene
14.8 Indole
14.9 Geosmin
14.10 2‐Bromo‐4‐methylphenol – Iodine, Oyster Taste
14.11 Heat Damage
14.12 Matters of Balance
14.13 Final Reflections
References
15 TDN and Tartrate Crystals: Faults or Not?
15.1 TDN
15.2 Tartrate Deposits
15.3 Final Reflections
References
16 Must Correction, Wine Correction, and Alcohol Reduction Using Membrane Technologies
16.1 Introduction
16.2 Membrane Processes Used in the Wine Industry
16.3 Clarification
16.4 Membrane Fouling
16.5 Must Correction, Wine Correction, and Alcohol Reduction
16.6 Fault Correction
16.7 Wine Stabilisation and pH Adjustment by Electrodialysis
16.8 Final Reflections
References
17 The Impact of Container and Closure Upon Wine Faults
17.1 Introduction
17.2 Glass Bottles
17.3 Bottle Closures
17.4 The Maintenance of Adequate Fee and Molecular SO2 in Bottled Wine
17.5 Cork Closures
17.6 Technical Corks and Agglomerated Corks
17.7 Diam Cork Closure
17.8 Synthetic Closures
17.9 Screw Caps
17.10 Vinolok
17.11 Some Advantages and Disadvantages of Various Closure Types
17.12 The Bottling Operation
17.13 PET Bottles
17.14 Cans
17.15 Bag‐in‐Box
17.16 Final Reflections
References
18 Best Practice for Fault and Flaw Prevention
18.1 The Wine Industry
18.2 HACCP
18.3 Standard Operating Procedures (SOPs)
18.4 Traceability
18.5 Winery Design
18.6 Cleaning and Sanitation
18.7 Good Practice Winemaking Procedures to Avoid Spoilage, Faults, and Flaws
18.8 The Use of Oenological Additions and Processing Aids
18.9 Routine Wine Analysis
18.10 Final, Final Reflections
References
Appendix A Levels of Free SO
2
Required to Give 0.5, 0.625, and 0.8 mg/l of Molecular SO
2
for Differing Wine pH Values
Further Reading
Easily Readable Books
Books with a More Scientific Approach
Glossary
Useful Websites
Index
End User License Agreement
Guide
Cover
Table of Contents
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Wine Faults and Flaws: A Practical Guide
Keith Grainger
Consultant in Wines and Wine TechnologyBroadway, UK
This edition first published 2021
© 2021 by John Wiley & Sons Ltd
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by law. Advice on how to obtain permission to reuse material from this title is available at http://www.wiley.com/go/permissions.
The right of Keith Grainger to be identified as the author of this work has been asserted in accordance with law.
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Limit of Liability/Disclaimer of Warranty
The contents of this work are intended to further general scientific research, understanding, and discussion only and are not intended and should not be relied upon as recommending or promoting scientific method, diagnosis, or treatment by physicians for any particular patient. In view of ongoing research, equipment modifications, changes in governmental regulations, and the constant flow of information relating to the use of medicines, equipment, and devices, the reader is urged to review and evaluate the information provided in the package insert or instructions for each medicine, equipment, or device for, among other things, any changes in the instructions or indication of usage and for added warnings and precautions. While the publisher and authors have used their best efforts in preparing this work, they make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives, written sales materials or promotional statements for this work. The fact that an organization, website, or product is referred to in this work as a citation and/or potential source of further information does not mean that the publisher and authors endorse the information or services the organization, website, or product may provide or recommendations it may make. This work is sold with the understanding that the publisher is not engaged in rendering professional services. The advice and strategies contained herein may not be suitable for your situation. You should consult with a specialist where appropriate. Further, readers should be aware that websites listed in this work may have changed or disappeared between when this work was written and when it is read. Neither the publisher nor authors shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages.
Library of Congress Cataloging-in-Publication Data
Names: Grainger, Keith, author.
Title: Wine faults and flaws : a practical guide / Keith Grainger.
Description: Hoboken, NJ, USA :Wiley-Blackwell, 2021. | Includes bibliographical references and index.
Identifiers: LCCN 2021001638 (print) | LCCN 2021001639 (ebook) | ISBN 9781118979068 (cloth) | ISBN 9781118979099 (adobe pdf) | ISBN 9781118979075 (epub)
Subjects: LCSH:Wine and wine making-Gaging and testing.
Classification: LCC TP511 .G73 2021 (print) | LCC TP511 (ebook) | DDC 641.2/2-dc23
LC record available at https://lccn.loc.gov/2021001638
LC ebook record available at https://lccn.loc.gov/2021001639
Cover Design: Wiley
Cover Image: © RomanKozhin/Shutterstock
To Paula.
Acknowledgements
So many people have imparted knowledge, opinions and assistance that have helped me write this work, that this list of acknowledgements is more notable for the numerous omissions than the names included. However, I would like to give particular thanks to Carlos de Jesus, Paulo Lopes and Joana Mesquita of Amorim, Matt Thomson of Kiwi‐Oeno Consultancy and Blank Canvas Wines, Sebastian Beaumont, Gordon Newton Johnson, Chris Alheit, the late, great Paul Pontalier of Château Margaux, Alfred Tesseron of Château Pontet‐Canet of Château Belgrave and other Dourthe properties, Jean‐Luc Columbo, Nicolas Joly, Sandro Bottega, Ernie Loosen, Raimund Prüm, José and Sebastien Zuccardi, Philip Tuck MW, Gordon Burns, and Evin Morrison of ETS Laboratories, Matthias Hüttl of LANXESS, Gordon Specht and Ann Dumond of Lallemand, Pascal Chatonnet, Gevork Arakelian, and Ken Walker. Finally, thanks to Nick Catley, Trevor Elliott and Hazel Tattersall for reviewing individual chapters.
Preface
Wines are produced today in over 65 countries, and it is often stated that production standards are higher than at any time in the 8000 or more years of vinous history. The consumer rightly expects any wine purchased to be of good quality, bearing in mind the price point, and free from fault, flaw, or taint. Wine critics, writers, producers, and retailers are all in the business of selling enjoyment and entertainment, for nobody has to drink wine – it is a beverage to be savoured. However, the incidences of faulty wines reaching the consumer are greater than would be regarded as acceptable in most other industries. It is claimed that such occurrences are less than was the case in recent recorded history, and it is true that the frequency of some faults, flaws, and taints being encountered in bottle (or other packaging) has declined in the last few decades. Gone are the days when a bottle of dry white Bordeaux would have more ‘struck‐match’ sulfur odours than the aromas of Sémillon or Sauvignon Blanc, and a white Bairrada exude the ‘Oloroso Sherry‐like’ aromas and bitter palate resulting from oxidation. Happily too, in recent years, there has been a considerable reduction in the occurrence of haloanisole contamination (often referred to as ‘cork taint’), which renders heavily affected wines undrinkable, having the musty odour of damp hessian or dry rot. However, incidences of certain faults and taints have increased, and issues that were once unheard of now affect many wines offered for sale. These include ‘reduced’ aromas, premature oxidation (premox), atypical ageing and, very much on the rise, smoke taint.
The reduction in the occurrence of some faults might have been expected with the increased sophistication and regulation of wine production, and the advance in scientific and technical knowledge of grape growers and winemakers. These, taken together with the utilisation of a vast array of high specification production equipment, might lead the consumer to believe that they are extremely unlikely to be faced with a faulty bottle of wine. This is sadly not the case. The increased incidence of some defects is, prima facie, surprising. However, the styles of wines that consumers want, or are perceived by the industry to want, have changed in the last 20 years or so. Grape harvests are often delayed until so‐called phenolic ripeness and, together with the effects of climate change, this has resulted in higher grape sugars, higher pH, and lower acidity. Each of these presents dangers. In the case of red wines, and particularly those at so‐called ‘entry‐level’, tannins are softer, and levels of residual sugar have often increased. Inexpensive wines are usually brought to the market very quickly, sometimes within a few months of harvest. Time is money, and there may be little time or budget for all desirable stabilisation procedures to take place. Finally, the consumer and especially the serious wine lover, wants wine to be a natural, agricultural product that has been turned into something wonderful by an artisan, not a scientist. Accordingly, many producers strive to make wine as ‘natural’ as possible, by reducing interventionist techniques and minimising chemical and biological additions, including those that may increase stability and prevent the onset of certain faults. It is also of concern that there is an increase in the incidence of mycotoxins in wines, due to their production by some of the microbial populations on vines. This is perhaps another consequence of climate change. Related off‐flavours, which were historically noted only occasionally, have been detected at a much higher frequency during the last 15 years.
This book provides a detailed examination and explanation of the causes and impact of the faults, flaws, and taints that may affect wines. As such, I believe that it will prove particularly valuable to winemakers, especially those at small, boutique wineries, wine technologists and quality control professionals. Wine critics, writers, educators, and sommeliers will also find the topics most relevant. With wine trade students and people venturing into the business of wine production in mind, the content is designed to be easily and speedily assimilated. The interested and knowledgeable wine‐loving consumer, including wine collectors and investors, will also find the book highly relevant and the basis for discussion at many tastings with like‐minded associates.
It is assumed that the reader has, at least, a basic knowledge of winemaking. Those who feel the need to brush up on the methods and techniques of wine production, from vine to bottle, are referred to ‘Wine Production and Quality 2nd Edition’ by Keith Grainger and Hazel Tattersall, also published by Wiley. However, this book is very suitable for those with limited scientific knowledge, and I have made every effort to maximise readability, with many anecdotes and expressed opinions, including my own. The chasm between general and scientific wine publications is both wide and deep, and I have attempted to bridge this as soundly as possible. There are several excellent books on viticulture and oenology, written in scientific language. Some of these are listed in the Further Reading. Alternatively, the easy to read articles and books penned by wine writers are seen by the scientific community as overflowing with anecdotes and lacking rigour. Of course, both approaches are valid, and I have made every effort to integrate them. I have tried to speak in terms that the general reader can understand. Although the number of studies and quality of research into chemical and microbiological faults in wine has increased considerably in the last couple of decades, most of this work remains within the confines of journals, which are largely unread outside of scientific and academic communities. On many occasions, results are inconclusive, conflicting, or the focus of some studies is seen as so narrow as to be of little relevance in the real world. Indeed many of the winemakers I have spoken to whilst researching this book have not been aware of the outcomes of recent research in important areas. Accordingly, there is still much misinformation and misunderstanding of the topics by producers, students and, of course, consumers.
Sections of individual chapters cover the science behind each fault, and for these, a very basic knowledge of organic chemistry and microbiology would be valuable. However, the scientifically challenged reader will find the text in includes helpful explanations, and the Glossary contains easy to understand definitions and descriptions of many scientific terms. I have included, at the end of each chapter, references to relevant publications and research papers (over 800 in total), concentrating on those in English and published within the last 20 years. I have also included references to earlier research that was particularly ground‐breaking. I have not included structural drawings, and there are very few chemical equations. I have not generally detailed isomers (isomers are where compounds have the same formula but differ from each other in the way the atoms are arranged). As the title of this work suggests, the focus is very much on practice – the book is certainly not aimed at the research scientist. In other words, I wish it to be a helpful manual for those who have little interest in the activities of the research lab, but to whom the excitement and challenges of the real world of wine are a way of life.
Keith Grainger
Saint‐André‐de‐Lidon
19 August 2020
Introduction
This book comprises a detailed examination of faults, flaws, and taints that can affect the quality and merchantability of wines. Technically, there is a distinction between a taint and fault that will be discussed in Chapter 1. However, wine consumers, merchants, and the press rarely observe such distinction, simply referring to the affected product as faulty. Some faults render affected wines unsaleable and undrinkable. Others that have a negative effect upon quality, enjoyment, or potential for ageing.
There are no reliable figures regarding the total global financial cost of faulty and tainted wines to producers, agents, distributors, and retailers. However, there can be no doubt that it runs into many £/€ billions annually. A recent estimate of the economic costs to EU wine producers of haloanisoles taint in wines (so‐called ‘cork taint’) is 700 million euros annually [1]. Product recalls due to matters other than incidences of physical contamination are relatively rare in the wine industry. When bottles of faulty wines do reach the consumer, the impact upon the producers' and suppliers' reputations is incalculable. Although the purchaser may not have the knowledge or skill to identify the fault in question, it is unlikely that they will repurchase any other bottles of the same wine, and may avoid the brand or producer in question. In other words, the consumer will believe the faulty wine to be very low quality. If they have no recourse to financial redress, as will most likely be the case for wines purchased many years previously and which they have been patiently nurturing in their ‘cellar’ in anticipation of the complex delights of full maturity, consumers may well feel somewhat cheated.
Wine is, without doubt, the most discussed food or drink in the world, and wine lovers readily communicate their experiences to friends, colleagues, and those who share a love for what can be the most exciting and individual of products. Today, such discussions are livelier and more influential than ever. With the proliferation of blogs and social media postings, the opinions of a consumer's peers are, for better or worse, as or even more important than those of professional critics and reviewers. Wine writers, authors, and journalists are generally hugely supportive of the wine industry, without which their profession would not exist. Most are ‘deeply in love’ with wine, or at least ‘fine wine’. However, it is the nature of writing that certain topics become ‘hot’ and are then developed and pursued for as long as the readership retains an interest. Amongst the wine faults that have received considerable coverage in specialist consumer media in the last decade or two are so‐called ‘cork taint’, ‘reduced’ aromas (often referred to as reduction or reductivity), premature oxidation (premox), and the aromas produced by Brettanomyces yeasts. When such topics are discussed in a global context, articles can be informative, but they can also weaken confidence and influence buying habits. However, if the coverage relates to individual producers, the damage inflicted can be both instant and ongoing. Reputational damage may be done simply by naming faulty wines submitted for assessment at comparative tastings conducted by specialist magazines, or for tasting competitions. By way of example, during the early years of this century, the influential USA published magazine Wine Spectator revealed the identity and details of several ‘high‐end’ Californian producers who had marketed wines tainted by 2,4,6‐trichloroanisole (TCA) and 2,4,6‐tribromoanisole (2,4,6‐TBA). These compounds are usually, and particularly in the case of 2,4,6‐TBA erroneously, referred to as ‘cork taint’. The negative impact upon the reputations of producers that had taken decades to build is apparent.
On the other hand, there are ‘under the radar’ faults that are seldom discussed in the popular wine media or amongst professionals. A prime example is ‘atypical ageing’, by which white wines very rapidly lose varietal character and develop undesirable aroma and palate characteristics. This fault, often confused with premature oxidation, has been described as ‘one of the most serious quality problems in white wine making in nearly 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 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 be uplifted by reaching for a glass of any good wine that has a story to tell.
References
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 Schneider, V. (2010). Primer on atypical aging.
Wines and Vines
4: 45–51.
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 Hanson, A. (1982).
Burgundy
. London: Faber.
5 Hanson, A. (1995).
Burgundy
, 2e. London: Faber.
6 Bakker, J. and Clarke, R.J. (2012).
Wine Flavour Chemistry
, 2e. Chichester: Wiley–Blackwell.
1Faults, 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 origins of wine production date back 8000 years, but the advances in the science and technology of production since World War II have outstripped those of the previous 79 centuries. There have been huge changes in the methods and improvements in standards of viticulture, although the reliance upon chemical fertilisers, pesticides, and herbicides that began in the 1960s declined only recently and was certainly both damaging to the environment and wine quality. The recent advent of geolocating and remote and proximal sensing and soil mapping, so‐called ‘precision viticulture’, and techniques to determine the hydric stress of vines have enabled growers to fine tune site‐specific management practices, including the precise addition of desirable nutrients and, where permitted, measured quantities of adjusted irrigation water to individual vineyard blocks, or even precise parts of blocks.
In the winery there have been numerous advances in equipment design and quality, and winemaking procedures. Some of the most important of these are:
Grape sorting and selection systems to exclude unripe, rotten, or damaged fruit: spectacular innovations have been made in the technology of sorting equipment in the last 15 years, including the use of sophisticated optical sorters;
The widespread utilisation from the 1970s of temperature‐controlled fermentation vessels (usually constructed of easily cleanable AISI 316 or 304 grade stainless steel), although the move today is ‘back’ to vats made of wood or concrete;
Development of numerous individual strains of cultured yeasts aiding the control of fermentations and development of required flavours;
A detailed understanding of
malolactic fermentation
(
MLF
) and the development of suitable inoculums for use when deemed necessary;
The utilisation of a wider range of extraction techniques including pre‐fermentation cold soaks, rack, and return (délestage), flash détente and thermo détente;
The use of gases namely carbon dioxide, nitrogen, and argon, primarily to avoid unwanted oxidation;
The development of programmable enclosed pneumatic presses that can be gas‐flushed;
The utilisation of in‐tank micro‐oxygenation, particularly for inexpensive red wines, that helps polymerise long‐chain tannins and is a valuable tool if costly barrel ageing is not to take place;
Pre‐bottling cold stabilisation, often also using the ‘contact process’, to precipitate crystals of potassium bi‐tartrate or calcium tartrate. Alternatively, membrane electrodialysis may now be employed for this purpose;
The availability of systems employing membrane technology, for must and wine correction, and filtration, including front end
microfiltration
(
MF
), cross‐flow (tangential) MF,
ultrafiltration
(
UF
),
reverse osmosis
(
RO
), and pervaporation;
the improvement in cork closure quality, particularly regarding the cleansing of corks of
2,4,6‐trichloroanisole
(
TCA
), and the introduction of effective alternative closures, including screw‐caps and synthetic closures with determined
oxygen transmission rate
s (
OTR
s).
Of course, small‐ and medium‐scale producers, many of whom are focussed upon the individuality and quality of their wines, may choose not to utilise ‘advanced’ techniques in the vineyard or winery, including oenological additives, processing aids, or sophisticated (and expensive) technical equipment.
1.3 Changes in Markets and the Pattern of Wine Consumption in Recent Decades
The changes in the pattern of wine consumption of wine during the last 40 years have been dramatic. There has been spectacular growth in sales in many countries that have limited domestic production and accordingly rely upon imports to satisfy demand: for example, in the United Kingdom, per capita wine consumption rose from just 2 l in the early 1960s to 19.7 l in 2010–2016 [1]. In 2018, UK per capita consumption was approximately 24.6 l [2]. However, during the same period, the per capita consumption of many traditional European wine production countries declined by some 50%, albeit mostly of very low quality wines. Prior to the 1970s only 10% of all wines were exported from producing countries, including intra‐Europe ‘exports’; by 2016 over one‐third of wine consumed globally was produced in another country [1]. The journey undertaken to market wine in both bottle and bulk may be many thousands of miles, from the New World to the Old or vice versa, or from the West to the East. This massive rise in exports has only been possible because of the considerable improvements in the technical quality and particularly the stability of the product sold. ‘It's a great wine to drink locally but it doesn't travel’, an often heard expression when visiting wine regions in the 1970s and 1980s, is but a distant memory today. Microfiltration and ultrafiltration using membrane technology have been important tools in ensuring clarity and stability of the product, particularly in the case of the output of large producers. Other membrane processes, including reverse osmosis (RO) have enabled producers to achieve product of reasonably consistent quality and in styles that the marketers and gatekeepers believe to be popular with a wide audience, including those who were traditionally not wine drinkers.
Several ‘new’ markets have emerged in the last decades, particularly Asian countries: in the last few years, sales in China have surpassed the wine industry's expectations, especially for so‐called ‘fine’ wines, although, at the time of writing, this market has been contracting. The interest amongst wine lovers in the qualities and differences in styles in wines produced around the world is also high, as evidenced by the proliferation of wine societies and attendance at tutored tasting and other wine events, the growth in wine ‘tourism’, and the plethora of blogs and other Internet and media discussions. Annual global wine sales are estimated to amount to 246 million hectolitres, the equivalent of nearly 33 billion 75 cl bottles [3]. The diversity of retailers selling wine, declining for many years, has recently increased. The typical consumer of everyday wines is most likely to make their purchase in a supermarket rather than in a specialist outlet, but the Internet has been the salvation of independent merchants, providing a relatively inexpensive marketing vehicle and access to a national or even international customer base. Many of these outlets offer high quality wines from small, individualistic producers and, in some cases, the production operations are ‘crowd‐funded’ by enthusiastic and loyal customers.
The quality and style of wines from any region, or any producer, however small or large, will not be totally consistent from vintage to vintage – indeed it is these variations that makes individual wines so exciting to wine lovers. In other words, the quality properties of the finished product are not precisely predictable, unlike the product of other drink production technologies [4]. There is constant debate how much winemaking is considered to be an art or science. However, there is no doubt that the use of modern winemaking techniques has led to wines moving closer in style [5], and this is decried by both passionate small producers and serious and educated wine lovers. Certainly the use of technological equipment has led to less incidences of some faults and flaws but paradoxically has also contributed to the increase in others.
Although almost all ‘fine wines’ are bottled at source (usually at the winery but sometimes elsewhere in the region of production), there has been an increase in the last decade in shipping ‘everyday wines’ in bulk and bottling at destination. In fact this was commonplace until the 1970: cheaper wines were often transported in ‘SAFRAP’ (lined mild‐steel containers) or even ships' tanks, and of course wine had been transported in barrels for many centuries. The return to bulk shipping for inexpensive wines has been largely driven by economic factors, together with the need to be seen to reduce the environmental impact of transportation. There are other pros and cons to bulk transportation, particularly from a quality perspective. International Organization for Standardization (ISO) tanks and flexitanks are the two most widely used transport containers, and wines may become tainted from poorly maintained or cleaned ISO tanks, or the ethylene vinyl alcohol (EVOH) copolymer liner of flexitanks, although such instances are thankfully very rare. There are historic incidences of wines being tainted with naphthalene on journeys from Australia to Europe. Flexitanks may also permit some undesirable oxygen ingression, albeit at a very low level – the permeability of the material has decreased considerably since the 1990s. As flexitanks are generally ‘single‐use’, contamination from previous contents is not usually a problem, but the disposable nature perhaps does not sit well the purported environmental advantages of bulk wine shipping. A defective seal on an ISO tank or the use of a flexitank material that is highly permeable could allow oxygen ingress leading to degradation of the entire contents. Wines to be transported in bulk will require adjustment and stabilisation before their journey, and often again prior to packaging at destination – the latter operations being outside of the control of the producer, who may nevertheless bear the brunt of any fallout resulting from product deterioration, or the manifestation of faults or flaws. On the positive side, temperature variations during transport are very often less for wines in large tanks, and the standards of bottling at a dedicated plant at destination may be higher than those in some wineries.
1.4 The Possible Impact of Some Fault Compounds Upon Human Health
Most of the faults discussed in this book, however unpleasant they may be from an organoleptic point of view, are not generally harmful to human health, at least at the concentrations in which they may be found in wine. Wine has a low pH and pathogens harmful to humans will not generally grow in the product (although we should remember that every year somewhere in the world people die as a result of consuming ‘fake’ wine). There are, however, some compounds of microbiological origin that may be found in wine that have been shown to be potentially harmful to humans. The most important of these are biogenic amines, ochratoxin A and ethyl carbamate. Ethyl carbamate is classified as ‘a probable human carcinogen’ (Group 2A) by the International Agency for Research on Cancer (IARC) [6], and several countries have set limits for its concentration in wine. Biogenic amines are toxic at high concentrations, and some people have an intolerance at the levels very often found in wine. Ochratoxin A is a known carcinogen in some animals and a suspected human carcinogen by IARC (Group 2B) [6]; accordingly limits to its concentration in wine have been set by the European Commission (EC) for member states of the European Union (EU) at 2 μg/l [7]. In addition, some chemical compounds which may be found in wine can be harmful, particularly phthalates that can be hormone disruptors in humans. Their presence in wine is always due to contamination from an external source, such as the epoxy resin lining of concrete fermentation or storage vats. In a research paper published in 2014, Pascal Chatonnet et al. revealed that significant quantities of dibutyl phthalate (DBP) had been found in 59% of the (French) wines analysed [8]. Although, with the possible exception of biogenic amines that can have a ‘blood‐like’ odour and taste, the above compounds do not influence aroma or taste, their presence in wine other than at very low levels should be regarded as a fault; more of this will be discussed in Chapter 14.
Of course ethanol, the alcohol of all fermented drinks, is a known carcinogen and is classified as ‘a human carcinogen’ (Group 1) by the IARC [6]. It is toxic if consumed in excess, and there are reported cases of death due to alcohol poisoning and other issues related to single acts of excessive consumption. Long‐term regular consumption of ethanol, other than at low levels, is also a causal factor in several carcinomas, liver diseases, and other health problems such as obesity, as wine lovers and imbibers of other alcoholic beverages are regularly made aware. Acetaldehyde is considered a fault in wine only if present in excessive amounts, which generally means having a negative impact upon aroma, but when associated with alcohol consumption is also classified as ‘a human carcinogen’ (Group 1) by the IARC [6].
1.5 Sulfur Dioxide and Other Possible Allergens
Some individuals are allergic to grapes or alcohol. However, some compounds may be present in wine that may cause allergic reactions. The most important of these is sulfur dioxide (SO2), which is generally added at several stages of the winemaking process for its antimicrobial and antioxidant properties. Even if none is added by the winemaker, most wine contains SO2 as it is naturally formed by yeast during the alcoholic fermentation. Allergic reactions to this compound, which is also used as a preservative in a wide range of foods and drinks, are not uncommon, and individuals with asthma may suffer particularly adverse reactions. Many other people show an intolerance. The total SO2 content of wine is regulated in the European Union (EU) and all major markets and any wine marketed that exceeds this must be considered as both faulty and illegal.
