I

Beer and brewing 1

1.1 Introduction *

1.2 Historical perspective 5

1.3 Current developments

1.4 Legislation

The brewing process 19

2.1 Overview

2.2 Beer types 19 2.2.1 Beverages related to beer 27

2.2.1.2 Sorghum beer 28

2.3 The brewing process 29

2.3.1 Malting 30

2.3.2 Adjuncts 33

2.3.3 Brewing water 34

2.3.5 Production of sweet wort 37

2.3.6 Wort boiling 42

2.3.7 Fermentation and post-fermentation processes 43

2.4 Wort composition 46

2.4.1 Carbohydrates 48

2.4.2 Nitrogenous components 51

2.4.3 Polyphenols 54

2.4.4 Lipids 56

2.4.5 Sulphur compounds 57

2.4.6 Minerals 58

2.4.7 Miscellaneous 60

2.5 High-gravity brewing 60

2.6 Glossary of brewing terms 63

The biochemistry of fermentation 69

3.1 Overview 69

3.2 Mass balance 71

3.3 Assimilation of wort nutrients 73

3.3.1 Sugar uptake 73

3.3.2 Uptake of wort nitrogenous components 76

3.3.3 Uptake of lipids 79

3.3.4 Metal ion uptake 80

3.4 Carbohydrate dissimilation 81

3.4.1 Carbon catabolite repression 86

3.4.2 Storage carbohydrates 89

3.4.2.1 Glycogen 89

3.4.2.2 Trehalose 92

3.4.3 Fermentable growth medium induced pathway 96

3.5 Requirement for oxygen 97 3.5.1 Synthesis of sterols and unsaturated fatty acids 100

3.6 Ethanol tolerance 108

3.6.1 Ethanol formation during fermentation 109

3.6.2 Ethanol toxicity 110

3.7 Formation of flavour compounds 113

3.7.1 Organic and fatty acids 116

3.7.2 Higher alcohols 117

3.7.3 Esters 121

3.7.4 Carbonyls 125 3.7.4.1 Vicinal diketones 128

3.7.5 Sulphur compounds 137

3.7.6 Shock excretion 142

4 Brewing yeast 143

4.1 Morphology, cytology and cellular function 143

4.1.1 Cell morphology 145 4.1.1.1 Cell composition 146

4.1.2 Cytology 149

4.1.2.1 Plasma membrane 149

4.1.2.2 Periplasm 151

4.1.2.3 Mitochondria 152

4.1.2.4 Vacuoles 155

4.1.2.5 Other cytoplasmic inclusions 156

4.1.3 Intracellular location of enzymes 158

4.2 Taxonomy and differentiation 158

4.2.1 Taxonomy of the Saccharomyces 158 4.2.1.1 Identification of yeasts 165

4.2.2 Taxonomy of ale and lager yeasts 166

4.2.3 Diversity and differences between ale and lager yeasts 168 4.2.3.1 Culture collections of brewing yeasts 171

4.2.4 Differentiation - an introduction 172

4.2.5 'Traditional' methods 173

4.2.5.1 Plate tests 173

4.2.5.2 Flocculation tests 175

4.2.5.3 Fermentation performance 177

4.2.5.4 Assimilation/fermentation 180

4.2.5.5 Immunology 181

4.2.5.6 Other approaches 182

4.2.6 'Modern' methods 183

4.2.6.1 Genetic fingerprinting - RFLP 183

4.2.6.2 Genetic fingerprinting - PCR 184

4.2.6.3 Genetic fingerprinting - karyotyping 187

4.2.6.4 Genetic fingerprinting - AFLP 189

4.2.6.5 Pyrolysis mass spectroscopy 189

4.2.6.6 Other approaches 193

4.3 Genetics - genome, cell cycle and modification 194

4.3.1 Introduction 194 4.3.1.1 Genetic nomenclature and definitions 195

4.3.2 The genome 195

4.3.2.1 Yeast genome project 195

4.3.2.2 Yeast genome project, human disease and pathogenicity 202

4.3.2.3 Yeast genome project and brewing yeast 206

4.3.2.4 Chromosome number 207

4.3.2.5 Ploidy 208

4.3.2.6 Chromosomal instability 212

4.3.2.7 Mitochondrial instability 217

4.3.3 Cell cycle 220

4.3.3.1 Cell division 220

4.3.3.2 Cell division and brewery fermentation 223

4.3.3.3 Stationary phase 225

4.3.3.4 Ageing 227

4.3.3.5 Death and autolysis 231

4.3.4 Genetic modification 232

4.3.4.1 Drivers for strain development 232

4.3.4.2 Approaches to strain development 234

4.3.4.3 Legislation, public perception and commercial implementation 236

4.4 Cell wall and flocculation 237

4.4.1 The cell wall - an introduction 237

4.4.2 Composition 239

4.4.2.1 Glucans 239

4.4.2.2 Mannoprotein 239

4.4.2.3 Chitin 241

4.4.2.4 Proteins 242

4.4.3 Cell wall and fermentation 243

4.4.3.1 Acid washing 244

4.4.3.2 Fining 244

4.4.3.3 Commercial applications 245

4.4.4 Flocculation - an introduction 245

4.4.5 Overview 247

4.4.6 Mechanism 248 4.4.6.1 Lectin-like proteins 248

4.4.6.2 Receptors 251

4.4.6.3 Interaction between receptors and lectin-like proteins 251

4.4.6.4 Genetics 253

4.4.6.5 Premature flocculation 253

4.4.6.6 Hydrophobicity 253

4.4.6.7 Zeta potential 254 4.4.7 Measurement 255

4.4.7.1 Current methods 256

4.4.7.2 New approaches 257

5 Fermentation systems 260

5.1 General properties of fermentation vessels 260

5.1.1 Materials used for vessel construction 261

5.1.2 Vessel hygiene 266

5.1.3 Fermenter capacity 267

5.1.4 Fermenter geometry 269

5.1.5 Monitoring and control 276

5.2 Fermentation rooms 279

5.2.1 Hygienic design of fermenting rooms 280

5.2.2 Temperature control of fermenting rooms 283

5.2.3 Control of carbon dioxide concentration 283

5.3 Traditional fermentation systems 284

5.3.1 Open fermenters 284

5.3.2 Closed square fermenters 286

5.3.3 Ale dropping system 287

5.3.4 Yorkshire square fermenters 287

5.3.5 The Burton Union system 289

5.4 Large-capacity fermenters 290

5.4.1 Cylindrical fermenters 291

5.4.2 Cylindroconical fermenters 295

5.4.3 Dual-purpose vessels 309

5.4.3.1 Asahi vessels 310

5.4.3.2 The Rainier uni-tank 311

5.4.3.3 Spheroconical fermenters 313

5.5 Accelerated batch fermentation 314

5.6 Continuous fermentation 316

5.6.1 Theoretical aspects 319

5.6.2 Continuous fermentation systems 324

5.6.2.1 Experimental continuous fermentation systems 324

5.6.2.2 Commercial continuous fermentation systems 334

5.7 Immobilised systems 346

5.7.1 Theoretical aspects 348

5.7.1.1 Methods of immobilisation 348

5.7.1.2 Effects of immobilisation on yeast physiology 351

5.7.1.3 Reactor types 359

5.7.2 Commercial systems 362

5.7.2.1 Alcohol-free beer 362

5.7.2.2 Continuous maturation 364

5.7.2.3 Primary fermentation with immobilised yeast 366

5.8 Pilot scale fermentation systems 369

5.9 Laboratory fermentation systems 370

5.9.1 Mini-fermenter 370

5.9.2 Stirred laboratory fermenters 371

5.9.3 Tall tubes 372

6 Fermentation management 377

6.1 Wort collection 377

6.1.1 Wort cooling and clarification 377

6.1.2 Wort oxygenation 382

6.1.3 Control of extract in fermenter 386

6.1.4 Control of yeast pitching rate 388

6.1.4.1 Direct weight of yeast cake 388

6.1.4.2 Metered addition of yeast slurry 389

6.1.4.3 Cone to cone pitching 390

6.1.4.4 Use of near infra-red turbidometry 391

6.1.4.5 Use of radiofrequency permittivity 394

6.1.5 Timing of wort collection 399

6.2 Post-collection additions 402

6.3 Monitoring fermentation progress 404

6.3.1 Monitoring temperature 404

6.3.2 Monitoring wort gravity 405

6.3.2.1 Sampling from fermenters 406

6.3.2.2 Off-line gravity measurement 408

6.3.2.3 Automatic measurement of gravity 409

6.3.3 Monitoring C02 evolution rate 413

6.3.4 Monitoring exothermy 415

6.3.5 Monitoring pH 416

6.3.6 Monitoring rate of oxygen assimilation 417

6.3.7 Monitoring yeast growth 418

6.3.8 Monitoring ethanol formation 419

6.3.9 Monitoring vicinal diketone concentration 420

6.3.10 Miscellaneous 422

6.4 Fermentation control 422

6.4.1 Effect of process variables on fermentation performance 423

6.4.1.1 Temperature 424

6.4.1.2 Yeast pitching rate 426

6.4.1.3 Wort dissolved oxygen concentration 428

6.4.1.4 Pressure 430

6.4.2 Automatic control regimes 432

6.4.2.1 Economics 433

6.4.2.2 Fermentation control by yeast oxygenation 433

6.4.2.3 Interactive control regimes 440

6.5 Fermentation management 445

6.5.1 Traditional top-cropping systems 446

6.5.2 Traditional lager fermentations 447

6.5.3 Modern closed fermentations 448

6.5.4 Troubleshooting abnormal fermentations 449

6.6 Recovery of carbon dioxide 453

6.7 Yeast recovery 455

6.7.1 Top-cropping systems 456

6.7.2 Bottom-cropping systems 457

6.8 Fermenter run-down 461

6.9 Secondary fermentations 464

6.9.1 Cask conditioning 464

6.9.2 Bottle-conditioned beers 466

7 Yeast management 468

7.1 Laboratory yeast storage and supply 468

7.1.1 Maintenance of stock cultures 468

7.1.1.1 Third-party storage 468

7.1.1.2 Storage by subculturing 469

7.1.1.3 Storage by drying 469

7.1.1.4 Storage by freezing in liquid nitrogen 471

7.1.2 Deposit, recovery and validation of identity 472

7.2 Yeast propagation 474

7.2.1 Theoretical 474

7.2.2 Propagation systems 477

7.2.2.1 Laboratory propagation 477

7.2.2.2 Brewery propagation 479

7.2.2.3 Use of dried yeast 486

7.3 Yeast handling in the brewery 486

7.3.1 Storage as pressed cake 489

7.3.2 Storage as a slurry 489

7.3.2.1 Properties of yeast slurries 492

7.3.2.2 Inter-brewery transport of yeast 493

7.3.3 Acid washing 494

7.4 Assessing yeast condition 496

7.4.1 Assessing yeast viability 497

7.4.2 Yeast vitality tests 501

7.4.2.1 Tests based on cellular composition 502

7.4.2.2 Measures of cellular activity 504

7.4.2.3 Fluorometric vitality tests 505

7.4.2.4 Vitality tests - a summary 507

7.5 Surplus yeast 508

8 Microbiology 510

8.1 Product spoilage 510

8.1.1 Susceptibility 510

8.1.2 Spoilage micro-organisms - bacteria 511

8.1.2.1 Gram-negative bacteria 513

8.1.2.2 Gram-positive bacteria 517

8.1.3 Spoilage micro-organisms - yeast 520

8.1.3.1 Saccharomyces wild yeast 521

8.1.3.2 Non-saccharomyces wild yeast 523

8.1.4 Sources 526

8.1.4.1 Biofilms 526

8.1.4.2 Air and process gases 530

8.1.5 Food safety 534

8.1.5.1 Nitrosamines 534

8.1.5.2 Biogenic amines 536

8.1.5.3 Pathogens 537

8.2 Minimising the risk 537

8.2.1 In the brewery 538

8.2.1.1 CiP and other processes 540

8.2.1.2 Pasteurisation 549

8.2.1.3 Sterile filtration 559

8.2.2 In the trade 560

8.3 Sampling and testing 565

8.3.1 Philosophy 566

8.3.1.2 Sampling plans and specifications 566

8.3.2 Methods - 'traditional' 567

8.3.2.1 Hardware 569

8.3.2.2 Media 569

8.3.2.3 Validation 574

8.3.3.1 ATP bioluminescence 575

8.3.3.2 Other rapid methods 582

8.3.4 Methods - current developments 584

8.3.4.1 Phenotypic methods 584

8.3.4.2 Genotypic methods 584

References 586

Index 638

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