Discrimination Testing in Sensory Evaluation

Lauren Rogers is an independent sensory science consultant in the UK with more than twenty years of practical experience. She is a member of the Society of Sensory Professionals, the Institute of Food Science and Technology's Sensory Science Group, the Sensometric Society and is also a member of the ASTM Sensory Evaluation Committee (E18). Joanne Hort is Fonterra Riddet Chair in Consumer and Sensory Science, and Director of the Food Experience and Sensory Testing (Feast) Lab, at Massey University in New Zealand. She was previously SABMiller Chair of Sensory Science at the University of Nottingham in the UK. She was a founding member of the Institute of Food Science and Technology's Sensory Science Group and the European Sensory Science Society. Sarah E. Kemp is a chartered sensory and consumer scientist with more than 35 years of experience in academia and industry. She has held senior positions at companies including Givaudan-Roure, Unilever Research and Cadbury Schweppes, as well as running her own consultancy business. She is a founding member and past Chair of the Institute of Food Science and Technology's Sensory Science Group and Chair of BSI Committee AW/012 Sensory Analysis. Tracey Hollowood as former Director of Sensory and Consumer Research for Sensory Dimensions Ltd, she has over 25 years of academic and industrial experience and has been published extensively. She established the UK’s first Post Graduate Certificate in Sensory Science and managed Nottingham University's Sensory Science Centre. She was a previous Chair of the Institute of Food Science and Technology (IFST) Midland Branch and the Sensory Science Group (SSG).

List of Contributors xv

Preface to the Series xvii

Preface xxi

Editor Biographies xxiii

Section 1 Introduction 1

1 Introduction 3
Sarah E. Kemp, Tracey Hollowood, Joanne Hort and Lauren Rogers

1.1 Introduction 3

1.2 Developments of Discrimination Testing 4

1.3 Discrimination as a Technique in Sensory Science 11

1.4 Applications 15

1.5 Overview of Book 16

References 19

2 General Considerations in Discrimination Testing 25
Harry T. Lawless

2.1 Introduction: Goals of Discrimination Tests 25

2.2 Types of Tests 27

2.3 General Test Considerations 32

2.4 Basic Statistical Analysis 35

2.5 Test Power and Sample Size; Equivalence and Similarity 38

2.6 Psychological Factors 42

2.7 Summary and Conclusions 43

References 44

3 An Overview of Sensory Discrimination Tests 49
Stella Lignou and Victoria Norton

References 65

4 Determining Individual Variation in Ability to Discriminate: Factors Affecting Responsiveness and Performance 67
Sara Spinelli, Caterina Dinnella and Erminio Monteleone

4.1 Introduction 67

4.2 Overview of the Factors Affecting Individual Differences in Oral and Olfactory Responsiveness 67

4.3 Factors Affecting Consumer and Trained Panelists Ability to Discriminate 74

4.4 Future Developments 76

4.5 Summary 77

Acknowledgments 77

References 77

5 Similarity or Equivalence Testing 85
Linda Lopez

5.1 Introduction 85

5.2 Practical and Common-sense Approach for Similarity Testing 87

5.3 Evolution of Similarity Testing Methodology 92

5.4 Example of Similarity Test Application in Claim and Recipe Change 98

5.5 Conclusion 102

References 102

6 Thurstonian Modeling and Signal Detection Theory 105
Michael J. Hautus 105

6.1 Signal Detection Theory and Thurstonian Modeling 105

6.2 SDT and Two Stimulus Alternatives 106

6.3 The A-Not A Task 108

6.4 The 2AFC (Paired Comparison) Task 120

6.5 Test Sensitivity 124

6.6 Closing Comments 127

References 127

7 Sureness Judgements and R-Index Calculations and Their Applications 131
Danielle van Hout and Hye-Seong Lee

7.1 Quantifications of Sensory Differences 131

7.2 R-Index 132

7.3 Sureness Judgements 133

7.4 Designing an R-Index Study, Using an A-Not A Task 133

7.5 R-Index Data Analysis 136

7.6 Applications 140

7.7 Future Developments 142

Appendix 144

References 148

8 Replicated Discrimination Testing 151
Michael Meyners and Bernard Thomas Carr

8.1 Introduction 151

8.2 General Considerations and Study Design 152

8.3 Notation 154

8.4 Statistical Testing to Show Product Differences 157

8.5 Descriptive Analysis and Parameter Estimation 165

8.6 Tests for Equivalence/Similarity 170

8.7 Replicated Preference Tests 171

8.8 Examples 174

8.9 Conclusions 185

8.10 Recommendations 186

8.11 Glossary and Notation 188

Acknowledgements 191

References 191

Section 2 Applications 197

9 Sensory Quality Measurement Based on SDT Discrimination 199
Hye-Seong Lee, Min-A Kim and Danielle van Hout

9.1 Introduction 199

9.2 A New Classification of Sensory Discrimination Tests and Their Relative Performance 200

9.3 Reference-based Discrimination Test Methodology: SDT Sensory Quality Measurements 209

9.4 Further Development 226

References 228

10 Discrimination Testing in Flavors and Fragrances: A Practical View 233
Karine Miot, Carlos Gómez-Corona and Isabelle Cayeux

10.1 Introduction to Discrimination Testing for Flavors and Fragrances 233

10.2 Discrimination Testing for Flavors 238

10.3 Discrimination Testing for Fragrances 248

10.4 Bringing Social Responsibility into Discrimination Testing for Flavors and Fragrances 256

10.5 What the Future Might Be in the Flavor and Fragrance Industries 259

10.6 Conclusions and Final Considerations 261

References 262

11 Kids as Sensory Detectives: Application of Discrimination Testing with Children to Identify If Differences Exist Between Two or More Products 265
Cindy Beeren

11.1 Introduction: Sensory Testing by Kids 265

11.2 Kids’ vs. Adults’ Sensitivities 266

11.3 Kids vs. Adults’ Preferences 268

11.4 Food Neophobia 269

11.5 So Why Use Kids? 270

11.6 Ethical Considerations 272

11.7 Environment for Testing with Kids 274

11.8 Sensory Screening 276

11.9 Training Session 279

11.10 Test Methods 281

11.11 Final Thoughts 285

References 287

12 Expanding Attribute-Specific Difference Tests with Multisample Paired Comparison Paradigms 291
Curtis R. Luckett

12.1 Introduction 291

12.2 Practical Considerations 299

12.3 Mosteller’s Extension of Thurstone 300

12.4 Bradley-Terry Models 301

12.5 Elo and mElo 302

12.6 Friedman-Style Rank Analysis 302

12.7 Considerations on Choosing an Appropriate Method 303

12.8 Future Developments 313

References 314

13 Summary 317
Sarah E. Kemp, Tracey Hollowood, Joanne Hort and Lauren Rogers

13.1 Introduction 317

13.2 Overall Comparison of Methods 317

13.3 Current/Recent Developments 320

13.4 Future 324

13.5 Conclusions 327

References 327

Index 331