Wine

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 Pre-fermentation 9 Fermentation 15 Post-fermentation 17 1.5.2 Red wines 22 Pre-fermentation 22 Fermentation 23 Post-fermentation 24 1.5.3 White wines 25 Pre-fermentation 26 Fermentation 27 Post-fermentation 28 1.5.4 Specialized wines 28 Rosé wines 28 Wines made from organically farmed grapes 29 Wines with added resin 30 Wines with low alcohol content 31 Sweet wines 31 Sparkling wine in Champagne 32 Sparkling wine by other methods 33 Wines by carbonic maceration 34 Wines by thermovinification 34 Wines matured Sur Lie 35 1.5.5 Fortified wines 35 Port wine 36 Sherry 38 Madeira 40 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 Resveratrol 46 Bibliography 48 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 Bibliography 87 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 Brix scale 94 Baumé and Oeschele scales 96 Prediction of alcohol content in the finished wine 96 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 Non-flavanoids 113 Flavan-3-ols 114 Flavonoids 116 Anthocyanins 117 3.6.2 Basic technology 118 Location of polyphenols in grapes 118 Use of the term ‘tannins’ and their classification 119 Grape tannins 120 Quantifying methods 121 HPLC measurements 122 Other methods 123 Analyses in grapes and during wine-making 124 3.6.3 Bitter constituents 127 White wines 127 Red wines 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 Basic chemistry 135 Technical use 135 Taste effects 136 3.8.2 Carbon dioxide 136 Formation and handling of CO 2 137 Sensory factors 137 3.8.3 Oxygen 138 Basic chemistry 138 Oxygen content in wines 139 Effect of oxygen on wine 141 3.9 Changes in maturation 142 3.9.1 ‘In-barrel’ ageing 143 Vats 143 Extraction from barrels 144 Oxidation in barrels 145 3.9.2 ‘In-bottle’ ageing 146 3.9.3 Oxidation–reduction (redox) potential 146 General 147 Nernst equation 147 Redox potentials in wine 148 Redox potentials during vinification 149 Bibliography 150 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 Units 163 Consistency of threshold odour levels 164 Threshold level difference between sniffing and tasting 164 Threshold levels in solutions of dissolved substances in water and in beverages 166 Relationship of threshold values to partition coefficients 168 Volatile compound concentration in the vapour phase 170 4.1.4 Flavour/odour descriptions 173 Use of word descriptions 173 Intensity of flavour/odour 175 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 Structure 181 Presence in wines 181 Flavour characteristics 182 4.3.2 Aldehydes 189 Presence in wine 189 Flavour characteristics 190 4.3.3 Ketones 190 Presence in wines 190 Flavour characteristics 190 4.3.4 Acetals 196 4.3.5 Alcohols 197 Presence in wines 197 Flavour characteristics 201 4.3.6 Lactones and furanones 201 Molecular structures 201 Presence in wines 205 Flavour characteristics 207 4.3.7 Acids 207 Presence in wines 207 Flavour characterisitcs 208 4.3.8 Nitrogeneous compounds 208 4.3.9 Phenols 209 Presence in wines 209 Flavour characteristics 209 4.3.10 Terpenes 209 Chemical structure 209 Presence in grapes/wines 213 Flavour characteristics 215 4.3.11 Pyrazines 216 Chemical structure 216 Presence in grapes/wines 216 Flavour characteristics 216 4.3.12 Sulfur compounds 219 Chemical structure 219 Presence in wines 219 Flavour characteristics 220 4.4 Changes during maturation 221 4.4.1 Fermentation and storage of wines ‘in-vat (tank)’ and ‘in-barrel (cask)’ 221 Fermentation 221 Storage 222 4.4.2 ‘In-bottle’ ageing 224 Changes in ester content 225 Substances produced by carbohydrate degradation 225 Sulfur compounds 225 Changes in terpenoids 225 Formation of substances from carotene breakdown 226 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 Bibliography 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 Sensory analysis 250 Quality tastings 251 Identifying wines by tasting 251 Sensory analyses used in research 252 Consumer tasting 252 Analytical tasting 253 5.2.10 Wine tasting information and analysis 254 Statistical 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 Cork taint 275 Mousiness 278 Ethylphenols 279 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 Bibliography 288 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 Bibliography 335 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 Standard operating temperature 347 Thermovinification 348 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 Bibliography 364 Appendix I 367 I. 1 Chemical formulae nomenclature 367 I.. 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 Optical activity 372 Chirality 373 Occurrence of enantiomers 375 I.. 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 Oxidation of phenolic compounds 380 Oxidation of procyanidins 383 Oxidation of non-flavanoid phenolic compounds 383 General 384 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 Tables of molecular formulae, weight and physical properties for each group of volatile compounds found in wine –Volatile esters 396 –Volatile aldehydes 399 –Volatile ketones 400 –Volatile alcohols 401 –Volatile furanones/lactones 402 –Volatile acids 403 –Volatile phenols 404 –Volatile terpenes 404 –Volatile methoxy pyrazines 405 –Volatile sulfur compounds 405 Index 407