Wine: Flavour Chemistry Book

Preface to the Second Edition xv

Preface to the First Edition xvii

1 Introduction 1

1.1 Scope of the book 1

1.2 Historical background 2

1.3 Wine flavour 3

1.4 Wine colour 6

1.5 Vinification 6

1.5.1 Vinification process 8

1.5.2 Red wines 22

1.5.3 White wines 25

1.5.4 Specialized wines 28

1.5.5 Fortified wines 35

1.6 Physiological effects 42

1.6.1 Attributed negative effects 43

1.6.2 Wine ethyl alcohol (ethanol) 43

1.6.3 Effects of phenols 45

2 Grape Varieties and Growing Regions 53

2.1 Wine grapes 53

2.2 Vine plant characteristics 56

2.3 Soil, climate and ripeness 57

2.3.1 Soil 57

2.3.2 Climate 58

2.3.3 Ripeness 64

2.4 Grape growing regions of the world 65

2.4.1 World wine production 65

2.4.2 Regions 66

2.5 Chemical composition of grapes, must and finished wines 71

2.5.1 Grapes and must 71

2.5.2 Finished wine 79

2.6 Quality control and classification of wines 79

2.6.1 France 79

2.6.2 Germany 82

2.6.3 Italy 83

2.6.4 Spain 84

2.6.5 Australia 84

2.6.6 USA 85

2.6.7 Quality control systems in the European Union 86

3 Basic Taste and Stimulant Components 89

3.1 Introduction 89

3.2 Basic taste perception 90

3.2.1 Role of taste 90

3.2.2 Taste perception mechanism 91

3.3 Ethyl alcohol 92

3.3.1 Measurement of ethyl alcohol content in wines 93

3.3.2 Measurement of sugar content in musts and wines 94

3.3.3 Sugar content of grapes and must 97

3.3.4 Chaptalization 98

3.4 Acidity 99

3.4.1 Contents of organic acids 100

3.4.2 Measurement of acid content 104

3.4.3 Acid taste 105

3.5 Sweetness 109

3.5.1 Chemical structure of sugars 109

3.5.2 Content/sweetness 109

3.6 Bitterness, astringency and mouthfeel 113

3.6.1 Basic chemistry 113

3.6.2 Basic technology 118

3.6.3 Bitter constituents 127

3.6.4 Astringency 127

3.6.5 Mouthfeel 128

3.7 Colouring matter 129

3.7.1 Colour of red wines 129

3.7.2 Colour of white wines 132

3.8 Other constituents 134

3.8.1 Sulfur dioxide 134

3.8.2 Carbon dioxide 136

3.8.3 Oxygen 138

3.9 Changes in maturation 142

3.9.1 ‘In-barrel’ ageing 143

3.9.2 ‘In-bottle’ ageing 146

3.9.3 Oxidation–reduction (redox) potential 146

4 Volatile Components 155

4.1 General 155

4.1.1 Sensory perception 156

4.1.2 Partition coefficients 158

4.1.3 Threshold flavour/odour levels 161

4.1.4 Flavour/odour descriptions 173

4.2 Volatile compounds detected in wines 175

4.2.1 Types of aroma in volatile compounds 178

4.2.2 Stereochemical effects in aroma volatile compounds 180

4.3 Contents and sensory evaluation data 180

4.3.1 Esters 180

4.3.2 Aldehydes 189

4.3.3 Ketones 190

4.3.4 Acetals 196

4.3.5 Alcohols 197

4.3.6 Lactones and furanones 201

4.3.7 Acids 207

4.3.8 Nitrogeneous compounds 208

4.3.9 Phenols 209

4.3.10 Terpenes 209

4.3.11 Pyrazines 216

4.3.12 Sulfur compounds 219

4.4 Changes during maturation 221

4.4.1 Fermentation and storage of wines 'in-vat (tank)' and 'in-barrel (cask)' 221

4.4.2 'In-bottle' ageing 224

4.5 Aroma detection and quantification 227

4.5.1 Gas chromatography 227

4.5.2 Sample preparation 228

4.5.3 Olfactometry 230

4.6 Chemical structure and physical properties 231

5 Wine Tasting Procedures and Overall Wine Flavour 239

5.1 Wine tasting 239

5.2 Wine tasting procedure 241

5.2.1 Tasting glass 241

5.2.2 Serving 243

5.2.3 Visual 243

5.2.4 Smell 244

5.2.5 Flavour 246

5.2.6 Interactions 247

5.2.7 Astringency 248

5.2.8 Judging the wine 249

5.2.9 Reasons for wine tasting 250

5.2.10 Wine tasting information and analysis 254

5.3 Factors influencing sensory perception 256

5.3.1 Threshold and sensitivity 257

5.3.2 Vocabulary 258

5.4 Balance of taste sensations in wine 258

5.5 Wine aromas 259

5.5.1 Odour/aroma classification 261

5.5.2 Aroma/odour characteristics of wines from particular grape varieties 262

5.5.3 Variants in Cabernet Sauvignon wine flavour 270

5.5.4 Variants of Chardonnay wine flavour 271

5.5.5 Flavour description of some other commercial wines 273

5.5.6 Off-odours and taints 274

5.6 Wine and food flavour 279

5.7 Aroma indices and statistical methods 282

5.7.1 Flavour unit concept 282

5.7.2 Odour activity unit 284

5.7.3 Multivariate and other statistical procedures 285

6 Sherry, Port and Madeira 291

6.1 Introduction 291

6.1.1 Sherry introduction 291

6.1.2 Port introduction 292

6.1.3 Madeira introduction 292

6.1.4 Comparisons between fortified wines 293

6.1.5 Ethyl alcohol – sensory effect 294

6.1.6 Ethyl alcohol – chemical effect 295

6.1.7 Sweetness 295

6.2 Sherry 295

6.2.1 Wine producers 296

6.2.2 Commercial wine styles 296

6.2.3 Wine writers’ comments 297

6.2.4 Grapes and must 297

6.2.5 Base wine 298

6.2.6 Maturation 299

6.2.7 Maturation changes under flor 299

6.2.8 Maturation changes without flor 301

6.2.9 Maturation with and without flor 302

6.2.10 Volatile compounds 302

6.2.11 Changes during maturation in phenolic compound content 309

6.3 Port wine 311

6.3.1 Port wine producers 311

6.3.2 Commercial Port wine styles 312

6.3.3 Wine writers’ comments 313

6.3.4 Grapes and must 314

6.3.5 Fermentation and base Port wine 315

6.3.6 Port wine compared to red table wine 317

6.3.7 Maturation 318

6.3.8 Colour changes during maturation 318

6.3.9 Volatile changes during maturation 322

6.4 Madeira 327

6.4.1 Madeira wine producers 327

6.4.2 Commercial Madeira wine styles 327

6.4.3 Wine writers’ comments 328

6.4.4 Sensory properties 328

6.4.5 Grapes and must 328

6.4.6 Base wines maturation 329

6.4.7 Volatile compounds 330

7 Formation Pathways in Vinification 341

7.1 Introduction 341

7.2 Process variables in vinification 342

7.2.1 Grapes 342

7.2.2 Yeast strain 344

7.2.3 Malo-lactic organisms 347

7.2.4 Temperature 347

7.2.5 Clarification procedures 349

7.2.6 Nutrient medium in fermentation 349

7.2.7 Maceration 351

7.3 Production of ethyl alcohol 351

7.4 Production of individual groups of compounds 352

7.4.1 Esters 352

7.4.2 Aldehydes 353

7.4.3 Ketones 354

7.4.4 Acetals 354

7.4.5 Higher alcohols 355

7.4.6 Furanones and lactones 356

7.4.7 Acids 357

7.4.8 Amines 357

7.4.9 Phenols (volatile) 357

7.4.10 Terpenes 359

7.4.11 Pyrazines 360

7.4.12 Sulfur compounds 360

7.5 Noble Rot 362

Appendix I 367

I.1 Chemical formulae nomenclature 367

I.1.1 Nomenclature for a homologous series of compounds (Greek number/word system) 367

I.1.2 System for substituent groups (derivatives) 368

I.1.3 System for substituting in long-chain compounds 368

I.1.4 System for characterizing esters 368

I.1.5 System for characterizing unsaturated compounds 369

I.1.6 Systems for esters, thiols and thio-compounds 369

I.1.7 Miscellaneous IUPAC recommendations 369

I.1.8 Alternative chemical names 369

I.1.9 Numbering systems for ring compounds 370

I.1.10 Trivial and common names for derivative alkanes and other compounds 370

I.1.11 General 371

I.2 Stereochemistry 371

I.2.1 Enantiomers 371

I.2.2 Geometrical (stereo-) isomers 375

I.2.3 Tautomerism 376

I.3 Chemistry of the oxidation of organic compounds 377

I.3.1 Auto- and enzymatic oxidation of lipids 378

I.3.2 Oxidation–reduction of alkyl alcohols and aldehydes 379

I.3.3 Oxidation of phenolic compounds 380

I.3.4 Oxidation–reduction (redox) potentials 384

I.4 Estimation of partition coefficients of volatile compounds in air/water 386

I.5 Grape varieties and cultivars 389

Appendix II 395

II.1 Units 395

II.2 Data sources 395

Index 407