Understanding Wine Chemistry

Wine chemistry inspires and challenges with its complexity, and while this is intriguing, it can also be a barrier to further understanding. The topic is demystified in Understanding Wine Chemistry, Special Mention awardee in the 2018 OIV awards, which explains the important chemistry of wine at the level of university education, and provides an accessible reference text for scientists and scientifically trained winemakers alike.

Understanding Wine Chemistry:

• Summarizes the compounds found in wine, their basic chemical properties and their contribution to wine stability and sensory properties

• Focuses on chemical and biochemical reaction mechanisms that are critical to wine production processes such as fermentation, aging, physiochemical separations and additions

• Includes case studies showing how chemistry can be harnessed to enhance wine color, aroma, flavor, balance, stability and quality.

This descriptive text provides an overview of wine components and explains the key chemical reactions they undergo, such as those controlling the transformation of grape components, those that arise during fermentation, and the evolution of wine flavor and color. The book aims to guide the reader, who perhaps only has a basic knowledge of chemistry, to rationally explain or predict the outcomes of chemical reactions that contribute to the diversity observed among wines. This will help students, winemakers and other interested individuals to anticipate the effects of wine treatments and processes, or interpret experimental results based on an understanding of the major chemical reactions that can occur in wine.

Autorentext

Professor Andrew L. Waterhouse, Department of Viticulture & Enology, University of California, Davis, USA.
Andrew Waterhouse received his PhD in organic chemistry from UC Berkeley, and has been a wine chemist at the University of California, Davis since 1991. He teaches wine analysis, graduate level wine chemistry, and an online introductory wine course, and is Chair of the Viticulture and Enology graduate studies program. Former graduate students and postdocs are academics, industry scientists and winemakers. His research lab has reported key wine oxidation reactions and has developed new methods to analyse wine components including those using LC-MS with isotope filtering, as well as NMR techniques. The research has focused on wine phenolics, oak compounds and oxidation products. In addition his lab has also been addressing the metabolic products of phenolics. He publishes in numerous international journals in the fields of chemistry and agriculture, and serves as a chief editor at the Journal of the Science of Food and Agriculture. See: waterhouse.ucdavis.edu.

Dr Gavin Sacks, Department of Food Science, Cornell University, USA.
Gavin Sacks received his PhD in analytical chemistry from Cornell University, and following post-doctoral studies in nutritional sciences and biogeochemistry he began as a faculty in food science at Cornell in 2007. He has served as Director of Undergraduate Studies for Cornell's interdepartmental Viticulture and Enology undergraduate major, in which he also teaches courses in wine analysis and in wine flavor chemistry. His research interests include the development of both low-cost and state-of-the-art approaches to analysis of odorants and other organoleptically important compounds; and applying these tools to understanding the role of plant genetics, cultural practices, and post-harvest processing on sensory attributes of foods and beverages, particularly of wine.

Dr David Jeffery, School of Agriculture, Food and Wine, University of Adelaide, Australia.
David Jeffery received his PhD in synthetic organic chemistry from Flinders University, and has been involved with wine chemistry for over a decade, initially as a researcher at The Australian Wine Research Institute before transitioning to The University of Adelaide in 2010. He teaches wine chemistry to undergraduate and Master level students, delivering topics associated with stabilization, clarification, distillation, wine aroma, polyphenols, and analytical methods. He also helped to develop and deliver a free online wine education course called Wine 101x, offered on the EdX platform. David's research areas extend to on many aspects of wine chemistry, with special interests in polyphenols and aroma compounds and their precursors. He utilizes his expertise in synthetic organic chemistry and natural product isolation, purification and characterization, along with experience in developing and applying analytical methods, to improve understanding of grape and wine chemistry, particularly in relation to chemical composition and quality.

Inhalt

Foreword xiii

Preface xv

Introduction xvii

The chemical diversity of wine xvii

What is wine? xvii

Chemical reactions in wine xx

Chemistry as a historical record xxi

The chemical senses and wine flavor xxi

References xxiv

Part A Wine Components and Their Reactions 1

1 Water and Ethanol 3

1.1 Introduction 3

1.2 Chemical and physical properties of water 3

1.3 Properties of ethanol and ethanolwater mixtures 4

1.4 Typical ethanol concentrations in wines 6

1.5 Sensory effects of ethanol 7

References 9

2 Carbohydrates 11

2.1 Introduction 11

2.2 Nomenclature, representation, and occurrence of sugars 11

2.3 Physical, chemical, and sensory properties of sugars 14

2.4 Polysaccharides 17

References 18

3 Acids 19

3.1 Introduction 19

3.2 Organic acids in wine 19

3.3 Organic acids, pH, and wine acidity 21

3.4 Acid adjustments 28

3.5 General roles of organic acids and pH in wine reactions 31

3.6 Sensory effects of acids 31

References 32

4 Minerals 34

4.1 Introduction 34

4.2 Origins of metals in wine 35

4.3 Reactions involving metals 35

4.4 Sensory effects of metals 37

4.5 Metals and wine authenticity 37

References 38

5 Amines, Amino Acids, and Proteins 40

5.1 Introduction 40

5.2 Chemistry of amines 40

5.3 Amino acids and related major nitrogenous compounds in wines 41

5.4 Nitrogenous compounds with health effects 44

5.5 Odor-active amines 45

References 48

6 Higher Alcohols 51

6.1 Introduction 51

6.2 Properties of higher alcohols 51

6.3 Origins and concentrations of higher alcohols 52

6.4 Six-carbon (C6) alcohols 53

6.5 Methanol 54

References 55

7 Esters 57

7.1 Introduction 57

7.2 Chemistry of esters 57

7.3 Esters in grapes 60

7.4 Esters formed during winemaking and storage 60

7.5 Sensory effects 65

References 66

8 Isoprenoids 68

8.1 Introduction 68

8.2 General chemical and sensory properties of isoprenoids 68

8.3 Monoterpenoids 69

8.4 Sesquiterpenoids 73

8.5 C13-Norisoprenoids 74

References 76

9 Aldehydes, Ketones, and Related Compounds 79

9.1 Introduction 79

9.2 Acetaldehyde 80

9.3 Short and medium chain aldehydes 80

9.4 Complex carbonyls 84

9.5 Carbonyl reactivity 85

References 86

10 Thiols and Related Sulfur Compounds 88

10.1 Introduction 88

10.2 Varietal sulfur aroma compounds polyfunctional thiols 91

10.3 Fermentative sulfur aroma compounds 93

10.4 Other sulfur-containing aroma compounds 94

Chemical principles: nucleophiles and electrophiles 95

References 97

11 Introduction to Phenolics 99

11.1 Introduction 99

11.2 Non-flavonoids 102

11.3 Flavonoids 103

References 104

12 Volatile Phenols 105

12.1 Introduction 105

12.2 Structure and chemical properties 105

12.3 Concentrations in wine and sensory effects 107

12.4 Origins in wine and effects on volatile phenol profile 107

References 110

13 Non-flavonoid Phenolics 112

13.1 Introduction 112

13.2 Hydroxycinnamates 112

13.3 Hydroxybenzoic acids 113

13.4 Stilbenes 114

Referenc…