Discrimination Testing in Sensory Evaluation E-Book
143,99 €
Mehr erfahren.
- Herausgeber: John Wiley & Sons
- Kategorie: Fachliteratur
- Serie: Sensory Evaluation
- Sprache: Englisch
Discrimination Testing in Sensory Evaluation
Provides a complete and unified approach to discrimination testing in sensory evaluation
Sensory evaluation has evolved from simple "taste testing" to a distinct scientific discipline. Today, the application of sensory evaluation has grown beyond the food industry—it is a sophisticated decision-making tool used by marketing, research and development, and assurance in industries such as personal care, household care, cosmetics, fragrances, automobile manufacturing, and many others. Sensory evaluation is now a critical component in determining and understanding consumer acceptance and behavior.
Discrimination Testing in Sensory Evaluation provides insights into the application of sensory evaluation throughout the entire product life cycle, from development to marketing. Filled with practical information and step-by-step guidance, this unique reference is designed to help users apply paired comparison tests, duo-trio tests, triangle tests, similarity tests, and various other discrimination tests in a broad range of product applications. Comprehensive chapters written by leading experts provide up-to-date coverage of traditional and cutting-edge techniques and applications in the field.
- Addresses the theoretical, methodological, and practical aspects of discrimination testing
- Covers a broad range of products and all of the senses
- Describes basic and more complex discrimination techniques
- Discusses the real-world application of discrimination testing in sensory evaluation
- Explains different models in discrimination testing, such as signal detection theory and Thurstonian modelling
- Features detailed case studies for various tests such as A- not AR, 2-AFC, and Ranking among others to enable practitioners to perform each technique
Discrimination Testing in Sensory Evaluation is an indispensable reference and guide for sensory scientists, in academia and industry, as well as professionals working in R&D, quality assurance and control, and marketing. It is also an excellent textbook for university courses and industry vocational programs in Sensory Science.
Sie lesen das E-Book in den Legimi-Apps auf:
Seitenzahl: 770
Veröffentlichungsjahr: 2024
Ähnliche
Table of Contents
Cover
Table of Contents
Series Page
Title Page
Copyright Page
Dedications
List of Contributors
Preface to the Series
References
Preface
References
Editor Biographies
Section 1: Introduction
1 Introduction
1.1 Introduction
1.2 Developments of Discrimination Testing
1.3 Discrimination as a Technique in Sensory Science
1.4 Applications
1.5 Overview of Book
References
2 General Considerations in Discrimination Testing
2.1 Introduction: Goals of Discrimination Tests
2.2 Types of Tests
2.3 General Test Considerations
2.4 Basic Statistical Analysis
2.5 Test Power and Sample Size; Equivalence and Similarity
2.6 Psychological Factors
2.7 Summary and Conclusions
References
3 An Overview of Sensory Discrimination Tests
References
4 Determining Individual Variation in Ability to Discriminate: Factors Affecting Responsiveness and Performance
4.1 Introduction
4.2 Overview of the Factors Affecting Individual Differences in Oral and Olfactory Responsiveness
4.3 Factors Affecting Consumer and Trained Panelists Ability to Discriminate
4.4 Future Developments
4.5 Summary
Acknowledgments
References
5 Similarity or Equivalence Testing
5.1 Introduction
5.2 Practical and Common‐sense Approach for Similarity Testing
5.3 Evolution of Similarity Testing Methodology
5.4 Example of Similarity Test Application in Claim and Recipe Change
5.5 Conclusion
References
6 Thurstonian Modeling and Signal Detection Theory
6.1 Signal Detection Theory and Thurstonian Modeling
6.2 SDT and Two Stimulus Alternatives
6.3 The A‐Not A Task
6.4 The 2AFC (Paired Comparison) Task
6.5 Test Sensitivity
6.6 Closing Comments
References
7 Sureness Judgements and R‐Index Calculations and Their Applications
7.1 Quantifications of Sensory Differences
7.2 R‐Index
7.3 Sureness Judgements
7.4 Designing an R‐Index Study, Using an A‐Not A Task
7.5 R‐Index Data Analysis
7.6 Applications
7.7 Future Developments
Appendix
References
8 Replicated Discrimination Testing
8.1 Introduction
8.2 General Considerations and Study Design
8.3 Notation
8.4 Statistical Testing to Show Product Differences
8.5 Descriptive Analysis and Parameter Estimation
8.6 Tests for Equivalence/Similarity
8.7 Replicated Preference Tests
8.8 Examples
8.9 Conclusions
8.10 Recommendations
8.11 Glossary and Notation
Acknowledgements
References
Section 2: Applications
9 Sensory Quality Measurement Based on SDT Discrimination
9.1 Introduction
9.2 A New Classification of Sensory Discrimination Tests and Their Relative Performance
9.3 Reference‐based Discrimination Test Methodology: SDT Sensory Quality Measurements
9.4 Further Development
References
10 Discrimination Testing in Flavors and Fragrances: A Practical View
10.1 Introduction to Discrimination Testing for Flavors and Fragrances
10.2 Discrimination Testing for Flavors
10.3 Discrimination Testing for Fragrances
10.4 Bringing Social Responsibility into Discrimination Testing for Flavors and Fragrances
10.5 What the Future Might Be in the Flavor and Fragrance Industries
10.6 Conclusions and Final Considerations
References
11 Kids as Sensory Detectives
11.1 Introduction: Sensory Testing by Kids
11.2 Kids’ vs. Adults’ Sensitivities
11.3 Kids vs. Adults’ Preferences
11.4 Food Neophobia
11.5 So Why Use Kids?
11.6 Ethical Considerations
11.7 Environment for Testing with Kids
11.8 Sensory Screening
11.9 Training Session
11.10 Test Methods
11.11 Final Thoughts
References
12 Expanding Attribute‐Specific Difference Tests with Multisample Paired Comparison Paradigms
12.1 Introduction
12.2 Practical Considerations
12.3 Mosteller’s Extension of Thurstone
12.4 Bradley‐Terry Models
12.5 Elo and mElo
12.6 Friedman‐Style Rank Analysis
12.7 Considerations on Choosing an Appropriate Method
12.8 Future Developments
References
13 Summary
13.1 Introduction
13.2 Overall Comparison of Methods
13.3 Current/Recent Developments
13.4 Future
13.5 Conclusions
References
Index
End User License Agreement
List of Tables
Chapter 2
Table 2.1 Discrimination Tests – Classification.
Chapter 3
Table 3.1 Summary of discrimination tests commonly utilized in a sensory sc...
Chapter 5
Table 5.1 Examples of parity and unsurpassed claims (Google search).
Chapter 6
Table 6.1 Frequencies for each outcome in a A‐Not A task for Judge 1, toget...
Table 6.2 Rating data for Judge 4 in the A‐Not A task. Ratings range from “...
Table 6.3 Best‐fitting parameter estimates and GOF statistics for the A‐Not...
Table 6.4 Rating data for Judge 4 in a 2AFC task using the same stimuli as ...
Chapter 7
Table 7.1 Example of data sheet obtained from a randomized blind presentati...
Table 7.2 Response matrix, summarizing the responses of Table 7.1.
Table 7.3 Response matrix, with letters indicating how to enter the data in...
Table 7.4 Response matrix and R‐index formulas for an A‐Not A test with mul...
Table 7.5 Response matrix and formulas for R‐index ranking.
Table 7.6 Response matrix with consumer preference ranking data.
Table 7.7 Results of the R‐index analysis of consumer preference ranking da...
Table 7.8 Summary of results of the preference ranking study.
Table 7.9 Critical values expressed in percentages of R‐index‐50%.
Chapter 8
Table 8.1 Number of panelists out of
n
= 30 with a given number of correct ...
Table 8.2 Observed and expected numbers of panelists out of
n
= 30 with the...
Table 8.3 Modified triangle test results for the comparison of plaice from ...
Table 8.4 Glossary of some key technical terms from this chapter.
Table 8.5 Explanation of mathematical notation and symbols.
Chapter 9
Table 9.1 Classification of various sensory discrimination test formats.
Table 9.2 Sample presentation of various sensory discrimination test method...
Table 9.3 Sensory panel results.
Table 9.4 Consumer study results.
Table 9.5 Sensory differences, are measured by consumers and the internal s...
Chapter 10
Table 10.1 Discriminative tests that are typically used in the F&F industry...
Table 10.2 Different objectives in a project in which discrimination tests ...
Table 10.3 Details of the triangular test: order of presentation by panelis...
Table 10.4 Details of the tetrad test: order of presentation by panelists (...
Table 10.5 Results of the R‐index test for samples B1 and B2.
Table 10.6 Evaluation stages that are usually used for laundry products....
Table 10.7 Different types of support used in perfumery.
Table 10.8 List of 26 fragrance allergens from European Union Cosmetics Reg...
Table 10.9 Different stages of evaluation of shampoo and conditioner.
Table 10.10 Results from the triangular test of the fragrances evaluated at...
Table 10.12 Effect of vulnerable panelist conditions in discriminative test...
Chapter 12
Table 12.1 List of methods and analysis methods to be covered in this chapte...
Table 12.2 Example data for a 3‐AFC test on vanilla flavor intensity.
Table 12.3 The number of combinations needed for a complete block design in...
Table 12.4 Example of the data used for this example.
Table 12.5 Observed votes for each sample. The cell values are the votes fo...
Table 12.6 Observed proportions of votes for each sample. The cell values a...
Table 12.7 Normal derivatives of observed probabilities.
Table 12.8 Difference between
S
′
j
and
S
′
i
values.
Table 12.9 Fitted probabilities, where the cell values are the proportion o...
Table 12.10 Arc sine treated squares of observed probabilities (
p
′).
Table 12.11 Arc sine treated squares of fitted probabilities (
p
″).
Table 12.12 Difference in arc sine treated squared probabilities.
Chapter 13
Table 13.1 Categories of discrimination tests.
Table 13.2 Some example discrimination test methods.
List of Illustrations
Chapter 2
Figure 2.1 A classification scheme for discrimination tests.
Figure 2.2 A sample ballot for a triangle test.
Figure 2.3 The data tabulation for a McNemar test is based on a 2 × 2 respon...
Chapter 4
Figure 4.1 Gender (W: women, M: men) and age class (1: 18–30 y.o.; 2: 31–45 ...
Figure 4.2 Gender (W: women, M: men) and age class (1: 18–30 y.o.; 2: 31–45 ...
Chapter 5
Figure 5.1 Statistical decision matrix showing the two types of error when s...
Figure 5.2 Incremental sensory degradation with sequential changes. In this ...
Figure 5.3 Theoretical relationship between expert and naïve consumer panel ...
Figure 5.4 Representation of an alternative level test for significant simil...
Figure 5.5 Comparison of proportion correct and proportion of discriminants ...
Figure 5.6 The ROC curve or receiver operating characteristics. The curves i...
Figure 5.7 Representation of how the Thurstone model proposes that the propo...
Figure 5.8 Representation of an example of the paradox of discriminatory non...
Figure 5.9 Different types of parity sensory claims.
Figure 5.10 Illustration of the use of
τ
as consumer decision criteria ...
Figure 5.11 Representation of product similarities using the Thurstonian mod...
Chapter 6
Figure 6.1 The evidence space and the decision space for the case of two sti...
Figure 6.2 Receiver operating characteristic curve for two judges with the s...
Figure 6.3 Receiver operating characteristic (ROC) curves for three cases of...
Figure 6.4 Evidence space for the 2AFC task. Circles represent equal‐likelih...
Figure 6.5 Empirical receiver operating characteristic (ROC) curves (i.e., d...
Figure 6.6 The standard error (SE) of
d
′
for different values of
d
′
...
Chapter 8
Figure 8.1 Estimated distribution of posterior probabilities for any number ...
Figure 8.2 Density of the posterior distribution of true discrimination rate...
Figure 8.3 Density of the posterior distribution of individual discriminatio...
Figure 8.4 Empirical distribution of success rates for the triangle test res...
Chapter 9
Figure 9.1 Sample presentation format and test instructions for various sens...
Figure 9.2 Powers of various discrimination tests by the number of tests (a)...
Figure 9.3 An example of A‐Not AR (a) and 2‐AFCR (b) response format using a...
Figure 9.4 Examples of A‐Not AR test protocols with three different types of...
Figure 9.5 Illustration of the data process on the pooled data obtained from...
Figure 9.6 Illustration of the data matrix for pair‐wise comparisons of the ...
Figure 9.7 Illustration of the results of discrimination
d'
and their co...
Figure 9.8 Illustrations of two different subject groups having discrepant d...
Figure 9.9 Illustration of recognition
d
′
(
d
′
Rec
) computation; (...
Figure 9.10 Scatter plot of
d'
values, regression line of trained panels...
Chapter 10
Figure 10.1 Discrimination tests used in the F&F industry based on their pro...
Figure 10.2 Different locations for the execution of discrimination tests fo...
Figure 10.3 Different locations for the execution of discrimination tests fo...
Figure 10.4 Seven different forms of tasting flavors, depending on where the...
Figure 10.5 A FAB was developed with two flavors (reference with test codes ...
Figure 10.6 Comparison of full‐sugar versus reduced‐sugar strawberry yogurt....
Figure 10.7 Samples used for the R‐index test of sausages with reduced salt ...
Figure 10.8 Panelist is asked to rub the towel three times from left to righ...
Figure 10.9 Discrimination testing of flavor applications with blind panelis...
Figure 10.10 Visually impaired panelists using a magnifying glass to read in...
Chapter 11
Figure 11.1 Example consent form.
Figure 11.2 Kids taste detective training (1).
Figure 11.3 Kids taste detective training (2).
Figure 11.4 Kids taste detective training (3).
Figure 11.5 Example of test paper without use of sample labels.
Chapter 12
Figure 12.1 Example of a Mosteller’s multisample extension of Thurstone.
Figure 12.2 Sweetness intensity across our samples.
Figure 12.3 Bayesian information criterion (BIC) considering 1–5 clusters of...
Figure 12.4 Sweetness intensity across five products for four clusters of co...
Figure 12.5
S
′ values for saltiness across all eight products.
Chapter 13
Figure 13.1 ASTM Survey Q1. Which one of the following best describes how yo...
Figure 13.2 ASTM survey Q5. Are your discrimination tests mainly for differe...
Guide
Cover Page
Table of Contents
Series Page
Title Page
Copyright Page
Dedication
List of Contributors
Preface to the Series
Preface
Editor Biographies
Begin Reading
Index
WILEY END USER LICENSE AGREEMENT
Pages
ii
iii
ii
v
xv
xvi
xvii
xviii
xix
xxi
xxii
xxiii
xxiv
1
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
197
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
317
318
319
320
321
322
323
324
325
326
327
328
329
331
332
333
334
335
336
337
338
339
340
341
342
343
A series of books on selected topics in the field of Sensory Evaluation
The first book in the Sensory Evaluation series is Sensory Evaluation: A Practical Handbook, published in May 2009. It focuses on the practical aspects of sensory testing, presented in a simple, ‘how to’ style for use by industry and academia as a step‐by‐step guide to carrying out a basic range of sensory tests. In‐depth coverage was deliberately kept to a minimum. Subsequent books in the series cover selected topics in sensory evaluation. They are intended to give theoretical background, more complex techniques and in‐depth discussion on application of sensory evaluation that were not covered in the Practical Handbook. However, they will seek to maintain the practical approach of the handbook and chapters will include a clear case study with sufficient detail to enable practitioners to carry out the techniques presented.
Discrimination Testing in Sensory Evaluation
Edited by
Lauren RogersJoanne HortSarah E. KempTracey Hollowood
This edition first published 2024© 2024 John Wiley & Sons Ltd
All rights reserved, including rights for text and data mining and training of artificial technologies or similar technologies. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by law. Advice on how to obtain permission to reuse material from this title is available at http://www.wiley.com/go/permissions.
The right of Lauren Rogers, Joanne Hort, Sarah E. Kemp and Tracey Hollowood to be identified as the editorial material in this work has been asserted in accordance with law.
Registered Office(s)John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USAJohn Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK
For details of our global editorial offices, customer services, and more information about Wiley products visit us at www.wiley.com.
Wiley also publishes its books in a variety of electronic formats and by print‐on‐demand. Some content that appears in standard print versions of this book may not be available in other formats.
Trademarks: Wiley and the Wiley logo are trademarks or registered trademarks of John Wiley & Sons, Inc. and/or its affiliates in the United States and other countries and may not be used without written permission. All other trademarks are the property of their respective owners. John Wiley & Sons, Inc. is not associated with any product or vendor mentioned in this book.
Limit of Liability/Disclaimer of WarrantyIn view of ongoing research, equipment modifications, changes in governmental regulations, and the constant flow of information relating to the use of experimental reagents, equipment, and devices, the reader is urged to review and evaluate the information provided in the package insert or instructions for each chemical, piece of equipment, reagent, or device for, among other things, any changes in the instructions or indication of usage and for added warnings and precautions. While the publisher and authors have used their best efforts in preparing this work, they make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives, written sales materials or promotional statements for this work. The fact that an organization, website, or product is referred to in this work as a citation and/or potential source of further information does not mean that the publisher and authors endorse the information or services the organization, website, or product may provide or recommendations it may make. This work is sold with the understanding that the publisher is not engaged in rendering professional services. The advice and strategies contained herein may not be suitable for your situation. You should consult with a specialist where appropriate. Further, readers should be aware that websites listed in this work may have changed or disappeared between when this work was written and when it is read. Neither the publisher nor authors shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages.
Library of Congress Cataloging‐in‐Publication Data applied for:
Hardback:9780470671405ePDF:9781118635452epub:9781118635445oBook:9781118635353
Cover Design: WileyCover Image: © Getty Images/iStockphoto
Dedications
This book is dedicated to:
Lawrence, Alexandra and JamesGeorge, Elizabeth, George and WilliamCampbell, Emma and LaraMike
List of Contributors
Cindy BeerenEdiBeeAlteaSpainWhyteleafe Community HubWhyteleafeUK
Isabelle CayeuxPerception & Cognitive NeurosciencesDepartment, Science & Research,dsm‐firmenichGeneva, Switzerland
Caterina DinnellaDepartment of Agriculture, Food,Environment and Forestry (DAGRI)University of FlorenceFlorenceItaly
Carlos Gómez‐CoronaHuman Insights Department, TasteTexture, and Health BU dsm‐firmenichNeuilly‐sur‐SeineFrance
Michael J. HautusSchool of Psychology, Faculty of ScienceThe University of AucklandAucklandNew Zealand
Tracey HollowoodFormerly Managing Director ofSensory Dimensions LtdUK
Joanne HortFood Experience and Sensory TestingLaboratory (Feast)Massey UniversityPalmerston NorthNew Zealand
Danielle van HoutAigoraRichmond, VAUSA
Sarah E. KempConsultant and formerly Head of GlobalSensory and Consumer GuidanceCadbury SchweppesUK
Min‐A KimDivision of Food and NutritionChonnam National UniversityGwangjuSouth Korea
Harry T. LawlessCornell UniversityIthaca, NYUSA
Hye‐Seong LeeDepartment of Food Science andBiotechnology, College of EngineeringEwha Womans UniversitySeoulSouth Korea
Stella LignouUniversity of ReadingReadingUK
Linda LopezS&T, Givaudan InternationalKemptthalSwitzerland
Curtis R. LuckettUniversity of TennesseeKnoxville, TNUSASCiFi FoodsSan Leandro, CAUSA
Michael MeynersDiscovery & Innovation Platforms,Procter & Gamble Service GmbHSchwalbach am TaunusGermany
Karine MiotSensory Department, Perfumery & BeautyBU dsm‐firmenichLondonUnited Kingdom
Erminio MonteleoneDepartment of Agriculture, Food,Environment and Forestry (DAGRI)University of FlorenceFlorenceItaly
Victoria NortonUniversity of ReadingReadingUK
Lauren RogersFreelance Sensory ScientistUK
Sara SpinelliDepartment of Agriculture, Food,Environment and Forestry (DAGRI)University of FlorenceFlorenceItaly
Bernard Thomas CarrCarr ConsultingEvanston, ILUSANational Wine and Grape Industry CentreCharles Sturt UniversityWagga Wagga, New South WalesAustralia
Preface to the Series
Sensory evaluation is a scientific discipline used to evoke, measure, analyze and interpret responses to products perceived through the senses of sight, smell, touch, taste and hearing (Anonymous 1975). It is used to reveal insights into the way in which sensory properties drive consumer acceptance and behavior and to design products that best deliver what consumers want. It is also used at a more fundamental level to provide a wider understanding of the mechanisms involved in sensory perception and consumer behavior.
Sensory evaluation emerged as a field in the 1940s. It began as simple “taste testing” typically used in the food industry for judging the quality of products such as tea, cheese, beer, and so on. From the 1950s to the 1970s, it evolved into a series of techniques to objectively and reliably measure sensory properties of products and was typically used to service quality assurance and product development. Through the 1980s and 1990s, the use of computers for data collection and statistical analysis increased the speed and sophistication of the field, so that sensory, consumer, and physicochemical data could be combined to design products that delivered to consumer needs.
Today, sensory evaluation is a sophisticated, decision‐making tool that is used in partnership with marketing, research and development, and quality assessment and control throughout the product lifecycle to enable consumer‐led product design and decision‐making. Its application has spread from the food industry to many others, such as personal care, household care, cosmetics, flavors, fragrances, and the automotive industry. Although it is already widely used by major companies in the developed market, its use continues to grow in emerging markets, smaller companies, and new product categories, as sensory evaluation is increasingly recognized as a necessary tool for competitive advantage.
The field of sensory evaluation will continue to evolve and it is expected that faster, more flexible, and more sophisticated techniques will be developed. Social networking tools are transforming the way research is undertaken, enabling direct and real‐time engagement with consumers. The use of sensory evaluation by marketing departments will continue to grow, particularly in leveraging the link between product sensory properties and emotional benefits for use in branding and advertising. Advances in other fields, such as genomics, brain imaging, and instrumental analysis, will be coupled with sensory evaluation to provide a greater understanding of perception.
Owing to the rapid growth and sophistication of the field of sensory evaluation in recent years, it is no longer possible to give anything but a brief overview of individual topics in a single general sensory science textbook. The trend is toward more specialized sensory books that focus on one specific topic, and to date, these have been produced in an ad hoc fashion by different authors/editors. Many areas remain uncovered.
We, the editors, wanted to share our passion for sensory evaluation by producing a comprehensive series of detailed books on individual topics in sensory evaluation. We are enthusiastic devotees of sensory evaluation, who are excited to act as editors to promote sensory science. Between us, we have over 120 years of industrial and academic experience in sensory science, covering food, household, and personal care products in manufacturing; food service; consultancy; and provision of sensory analysis services at local, regional, and global levels. We have published and presented widely in the field; taught workshops, short courses, and lecture series; and acted as reviewers, research supervisors, thesis advisors, project managers and examiners. We have been active in many sensory‐related professional bodies, including the Institute of Food Science and Technology Sensory Science Group, of which many of us are past Chairs, the European Sensory Science Society, of which one of us is a past Chair, the Institute of Food Technologists, the British Standards Institute, and ASTM International, to name but a few. As such, we are well placed to have a broad perspective of sensory evaluation and pleased to be able to call on our network of sensory evaluation colleagues to collaborate with us.
The book series Sensory Evaluation covers the field of sensory evaluation at an advanced level and aims to:
be a comprehensive, in‐depth series on sensory evaluation
cover traditional and cutting‐edge techniques and applications in sensory evaluation using the world’s foremost experts
reach a broad audience of sensory scientists; practitioners; and students by balancing theory, methodology, and practical application
reach industry practitioners by illustrating how sensory can be applied throughout the product life cycle, including development, manufacture, supply chain, and marketing
cover a broad range of product applications, including food, beverages, personal care, and household products.
Our philosophy is to include cutting‐edge theory and methodology, as well as illustrating the practical application of sensory evaluation. As sensory practitioners, we are always interested in how methods are actually carried out in the laboratory. Often, key details of the practicalities are omitted in journal papers and other scientific texts. We have encouraged authors to include such details in the hope that readers will be able to replicate methods themselves. The focus of sensory texts often tends to be food and beverage products assessed using olfaction and taste. We have asked authors to take a broad perspective to include non‐food products and all the senses.
The book series is aimed at sensory professionals working in academia and industry, including sensory scientists, practitioners, trainers, and students; and industry‐based professionals in marketing, research and development, and quality assurance/control, who need to understand sensory evaluation and how it can benefit them. The series is suitable as:
reference texts for sensory scientists, from industry to academia
teaching aids for senior staff with responsibility for training in an academic or industrial setting
course books, some of which to be personally owned by students undertaking academic study or industrial training
reference texts suitable across a broad range of industries; for example, food, beverages, personal care products, household products, flavors, fragrances.
The first book in the series, Sensory Evaluation: A Practical Handbook, was published in May 2009 (Kemp et al. 2009). This book focuses on the practical aspects of sensory testing, presented in a simple, “how to” style for use by industry and academia as a step‐by‐step guide to carry out a basic range of sensory tests. In‐depth coverage was deliberately kept to a minimum. Further books in the series cover the basic methodologies used in the field of sensory evaluation: discrimination testing, descriptive analysis (Kemp et al. 2018), time‐dependent measures of perception (Hort et al. 2017), and consumer research. They give theoretical background, more complex techniques, and in‐depth discussion on application of sensory evaluation, while seeking to maintain the practical approach of the handbook. Chapters include clear case studies with sufficient detail to enable practitioners to carry out the techniques presented. Later books will cover a broad range of sensory topics, including applications and emerging trends.
The contributors we have selected are world‐renowned scientists and leading experts in their field. Where possible, we have used originators of techniques. We have learned a lot from them as we have worked with them to shape each book. We wish to thank them for accepting our invitation to write chapters and for the time and effort they have put in to making their chapters useful and enjoyable for readers.
We would also like to thank our publisher, Wiley Blackwell, and the team for seeing the potential in this series and helping us bring it to fruition. We would also like to thank the anonymous reviewers of the series for their constructive comments.
We hope you will find the Sensory Evaluation book series both interesting and beneficial, and enjoy reading it as much as we have producing it.
Sarah E. KempJoanne HortTracey HollowoodLauren Rogers
References
Anonymous (1975).
Minutes of Division Business Meeting. Institute of Food Technologists – Sensory Evaluation Division
. Chicago, IL: IFT.
Kemp, S.E., Hollowood, T., and Hort, J. (2009).
Sensory Evaluation: A Practical Handbook
. Oxford: Wiley‐Blackwell.
Kemp, S.E., Hollowood, T., and Hort, J. (2018).
Descriptive Analysis in Sensory Evaluation
. Oxford, UK: Wiley‐Blackwell.
Hort, J., Kemp, S.E., and Hollowood, T. (2017).
Time‐Dependent Measures in Sensory Evaluation
. Oxford, UK: Wiley‐Blackwell.
Preface
Discrimination tests are one of the key sets of methods in a sensory scientist’s toolbox. The aim of this book is to provide a comprehensive and up‐to‐date overview of the area, the tests, and their applications.
Discrimination tests are covered in classic general sensory science texts, including Meilgaard et al. (2016), Lawless and Heymann (2010), and Stone et al. (2020). These have limited space to give to the topic, which makes it difficult to strike a balance between theory and practical application. To the editors’ knowledge, there are two previous publications devoted to discrimination tests. Bi (2015, updated from the first edition in 2008) produced a very detailed book that thoroughly covers the statistical aspects of discrimination testing, as well as information about consumer emotions, time intensity, and shelf‐life. Rogers (2017) edited a practical handbook for sensory scientists with chapters and case studies dedicated to the most popular sensory discrimination tests.
The editors saw a need for a book devoted to discrimination testing that would provide in‐depth theoretical and practical coverage of traditional and recently developed approaches, as well as cover several of the many applications of sensory science such as food, home and personal care, and ingredient testing. In addition, the book also considers discrimination testing with different subjects and those with differing discrimination abilities, as well as replicated discrimination tests and the use of discrimination tests in determining sensory quality. The scope of this book includes history, theory, techniques and applications of discrimination tests. The book also includes case studies to bring the applications to life, making it an essential reference for sensory scientists.
The book is structured in two sections. Section 1 is an introduction covering general topics in discrimination testing, including history, general considerations, determining discrimination abilities, similarity, and approaches to replicated tests. This section also delves into Thurstonian modeling and the use of sureness judgments to quantify the size of the sensory differences. Section 2 covers some applications of discrimination testing such as the use of children to conduct the tests, the use of attribute‐specific tests with many samples, and conducting discrimination tests in the flavors and fragrances industries.
Each chapter includes theory, psychological aspects, methodology, statistical analysis, applications, practical considerations, case studies and examples, future developments, and a reference list. The aim is to give a balance between theory and practice, with enough theory for readers to fully understand the background and underlying mechanisms of the technique, and in many instances enough detail to enable the reader to carry out the methodology.
We thank all authors for giving their time and effort to their chapter despite their busy schedules, and for their patience with the process.
We hope you find this book as interesting and beneficial to read as we did to produce.
Lauren RogersTracey HollowoodJoanne HortSarah E. Kemp
References
Bi, J. (2015).
Sensory Discrimination Tests and Measurements: Sensometrics in Sensory Evaluation
. Wiley.
Bi, J. (2008).
Sensory Discrimination Tests and Measurements: Statistical Principles, Procedures and Tables
. Wiley.
Meilgaard, M., Civille, G., and Carr, B. (2016).
Sensory Evaluation Techniques
. Boca Raton, Florida: Taylor & Francis.
Lawless, H.T. and Heymann, H. (2010).
Sensory Evaluation of Food. Principles and Practices. Sensory Evaluation of Food – Principles and Practices
. New York: Springer.
Rogers, L. (2017).
Discrimination Testing in Sensory Science: A Practical Handbook
. Woodhead Publishing.
Stone, H., Bleibaum, R., and Thomas, H.A. (2020).
Sensory Evaluation Practices
. Academic press.
Editor Biographies
Tracey Hollowood BSc (Hons), PhD, is the 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 postgraduate 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).
Joanne Hort, BEd (Hons), PhD, CSci, FIFST, MNZIFST, RSensSci, is the Fonterra‐Riddet Chair of Consumer and Sensory Science at Massey University in New Zealand (NZ) following on from her various academic roles, latterly SABMiller Chair of Sensory Science at the University of Nottingham. Initially, Professor Hort studied food technology and began her career in teaching. However, she returned to university to receive her doctorate concerning the modelling of the sensory attributes of cheese from analytical and instrumental measures in 1998 and then took up a post as lecturer at Sheffield Hallam University. She was appointed as a lecturer in Sensory Science at the University of Nottingham in 2002. There she established the University of Nottingham Sensory Science Centre, obtaining her Chair in 2013. Her multidisciplinary approach combining analytical, brain imaging and sensory techniques provided rich insight into multisensory interactions, individual variation, temporal changes in flavor perception and the emotional response to sensory properties. In 2017, she took the position of inaugural Fonterra Riddet Chair in Consumer and Sensory Science at Massey University where she has established the Food Experience and Sensory Testing (Feast) lab, complete with digital immersive space for research on emotional response in ecologically valid environments. She has over 120 publications and sits on the editorial board for Food Quality and Preference. She is a fellow of the Institute of Food Science and Technology (IFST), member of the NZIFST and NZ Royal Society. She is vice president of the Pangborn Sensory Science Trust, a founder member and past chair of the European Sensory Science Society, and a founder member and past chair of the UK IFST Sensory Science Group.
Sarah E. Kemp, BSc (Hons), PhD, CSci, FIFST, RSensSci, is a chartered sensory and consumer science professional with more than 35 years of experience in academia and industry. Dr Kemp gained a BSc in Food Technology in 1986 and a PhD in Taste Chemistry in 1989 from the Food Science and Technology Department at the University of Reading, UK. In 1990, she did a postdoctoral research fellowship in sensory science at the Monell Chemical Senses Center in Philadelphia, USA. Dr Kemp has held many positions in industry, including manager of Sensory Psychology (US) and director of European Consumer and Marketing Research (France) in the Fragrance Division at Givaudan; product area leader and sensory science leader in Foods Consumer Science at Unilever Research, Colworth, UK; head of Global Sensory and Consumer Guidance at Cadbury Schweppes, UK; and director of Sensory and Consumer Services at Reading Scientific Services Limited, UK. Dr Kemp has also set up and run her own consultancy service and catering company. She has written numerous scientific articles in the field of sensory evaluation, has provided sensory training courses, including lecturing on the European Masters Course in Food Science, and has worked on bodies developing standards in sensory evaluation, including ASTM and the British Standards Institution, where she is chair of Committee AW/012 Sensory Analysis. She is a fellow of the Institute of Food Science and Technology and a founder member, past chair, and examiner for the IFST’s Sensory Science Group, as well as being a member of other professional sensory societies and a past Governor of East Kent College, UK.
Lauren Rogers is a freelance sensory scientist living in the beautiful Staffordshire Peak District. Lauren fell in love with sensory science in the early 1990s when she worked for Dalgety Plc, a food ingredients company. Later, she worked for GlaxoSmithKline, mainly on beverages such as Ribena and Horlicks. Lauren became a freelancer in 2009 and, as well as working for several different clients on many different product types and many different qualitative and quantitative methods, Lauren lectures on sensory science at the University of Nottingham and Le Cordon Bleu. Lauren is particularly interested in the sensory, consumer, and emotional attributes of brands; sensory shelf‐life; panel performance; and sensory claim substantiation. She has experience in many food products including ingredients, snack products, drinks, and pet‐food. She also has worked on many home and personal care products such as shampoos, conditioners, toothpastes, and creams. Lauren is a fellow of the Institute of Food Science and Technology (IFST) and an active member of the IFST’s Sensory Science Group, maintaining their sensory science qualifications. She is also a member of the Market Research Society, the Sensometrics Society, the Society of Sensory Professionals and the ASTM E‐18 (Sensory) Committee. Lauren is a member of the British Standards Society working on various international sensory science standards. Lauren has previously published two books, Sensory Panel Management and Discrimination Testing in Sensory Science.
Section 1Introduction
1Introduction
Sarah E. Kemp1, Tracey Hollowood2, Joanne Hort3 and Lauren Rogers4
1 Consultant and formerly Head of Global Sensory and Consumer Guidance, Cadbury Schweppes, UK
2 Formerly Managing Director of Sensory Dimensions Ltd, UK
3 Food Experience and Sensory Testing Laboratory (Feast), Massey University, Palmerston North, New Zealand
4 Freelance Sensory Scientist, UK
1.1 Introduction
Sensory discrimination tests are methodologies used in fields such as foods and beverages, home and personal care, cosmetics, and consumer goods to assess whether two samples are perceptibly different. The two samples being tested generally come from two production batches. These different batches might use, for example, different ingredients, different manufacturing processes, or different packaging. Discrimination tests are also used to evaluate and quantify individuals' abilities to perceive and differentiate various sensory attributes or a holistic difference between products. Participants are typically presented with pairs of products and are tasked with identifying differences or similarities in sensory characteristics, such as appearance, aroma, taste, flavor or texture. These tests play a crucial role in quality control, product development, and market research, for example, providing valuable insights into consumer preferences and aiding in the improvement of product formulations based on perceived sensory attributes.
1.1.1 Discrimination Testing as a Tool
Imagine that you are the new product development manager for a major snack manufacturer and have been tasked with an innovative global wellness project to further reduce the levels of salt and fat in the company’s flagship product. Several designs of experiment studies are currently being discussed by the team and the next step is to discuss the project timings for the assessment of the sensory aspects of the products arising from these experiments. You have a meeting with the sensory manager to discuss the plans and the sensory methods available to help meet the project’s action standards. There are several classes of sensory methods available to you, including descriptive, temporal and consumer methods, however, you agree with the global sensory manager that discrimination tests1 are the best choice for this stage of the project as the differences between products should be slight: there is no point in conducting a discrimination test on products that are obviously different. The sensory manager has explained that if you need to know how products are different, you will need a different method (for example, quantitative descriptive analysis or free choice profiling). The sensory discrimination tests will allow you to determine if consumers will notice the difference between the chemically and physically different products from the experimental design studies and the current gold standard products.
To use a sensory discrimination test, three things are usually required: people to assess the samples, the choice of the test and some samples to assess. Obviously, a sensory scientist is also required to choose and administer the test, as well as to analyze and report the results. The person who takes part in the test is often someone who has been screened for their sensory acuity (ISO 2023) and trained in the test method, although they might also be naïve consumers. By training in the method first, the participant is focused on the items in the test and not the execution of the test itself. This person assesses the items presented to them using the training they received, answering the question posed by the test; for example, selecting the odd sample in a discrimination test known as a triangle test (Sinkinson 2017) or rating the difference between samples on a scale (Whelan 2017). The results from all participants in the test are then analyzed to make a final decision based on the objectives and action standard(s).
There are many different sensory discrimination tests available to the sensory scientist to help meet the types of objectives they might encounter. The choice of test will depend on several factors, with the primary considerations being the type of product being tested and the objectives of the test. There is a tendency for businesses to habitually use one discrimination test for all objectives, but not all objectives are equal: for an interesting discussion about the choice of sensory test related to the objective(s) of the research, see Lawless and Heymann (2010, pp. 8–10).
When the focus of the discrimination test is to answer a product‐related question, the intended use of the results and the test’s position within the project stages are important factors in the choice of test (Meilgaard et al. 2016).
1.2 Developments of Discrimination Testing
Sensory discrimination testing began early in the 20th century and was originally referred to as difference testing (Meiselman et al. 2022), however, the initial “discrimination tests” were conducted by Weber and Fechner in the early 19th century to examine the relationship between physical stimuli and sensory experience (David 1963). This field of study, now referred to as psychophysics, was characterized by the researchers’ belief that sensations could not be measured directly. Consequently, they employed a variety of indirect methods and experiments to gauge perception. Weber’s experiments in 1834 explored the “just noticeable difference” between different weights using blindfolded subjects (Holden et al. 2011). He found that the detectable difference was proportional to the initial weight. This method has since become known as “the method of constant stimuli” and bears resemblance to paired comparison methods such as the 2‐alternative forced choice test commonly used in sensory science today.
Fechner expanded on Weber’s findings, formulating Weber’s law and introducing two additional methods: “the method of limits” and “the method of adjustment or average error.” Although the latter method is challenging to implement in food research, as it requires subjects to adjust levels of ingredients such as salt, the method of limits – which involves changing the stimulus incrementally and asking subjects if they perceive any sensation – is akin to same‐different tests and the ascending forced‐choice method of limits employed to determine thresholds today. Thus, the technique of comparing pairs of stimuli began with Weber and was further refined by Fechner (Fechner 1860; Lawless and Heymann 2010).
Louis Thurstone (1927) also made extensive use of paired comparison tests in his psychophysical work to describe the discrimination process, which has been of great interest in the field of sensory discrimination testing. Researchers employ Thurstonian modelling and signal detection theory (SDT) to study differences in people’s sensitivity to specific stimuli.
Perhaps the earliest example of a sensory discrimination test in the literature with a focus on food is Fisher’s famous article on tea tasting, which would become the cornerstone reference for hypothesis testing. The test originated in the 1920s in Cambridge, when a group of friends, including Ronald Fisher, were debating the proper way to pour tea and whether the milk should be added to the cup before or after the tea. One member of the group claimed that she could discern whether the milk had been added first or last. To test this claim, Fisher designed an experiment to determine whether she could accurately identify the order in which the milk was added (Fisher 1935). The original documentation provides an interesting account of the experiment’s design, statistical analysis, and results. Although the method employed in the tea testing was not given a name, Gridgeman (1959) referred to it as a “double‐tetrad sorting design.” Today, we would likely classify it as an octad or under the M + N tests (Lockhart 1951).
Of course, food discrimination testing has been in use for much longer than the past nine decades. Sensory tests, though informally, have been employed to assess food edibility and check drinking water quality for centuries. Additionally, nonfood testing has also been conducted throughout history, such as evaluating the suitability of housing, e.g. caves and weapons, e.g. assessing the sharpness of flint tools (Meilgaard et al. 2016).
Ranking is possibly the earliest sensory discrimination method, with references to its use for assessing preferences for eggs and sweetcorn in very early studies (as reported by Morse 1942). This type of grading, although not a formal sensory test, was one of the first methods used to assess the quality of a product. Experts would assess the quality based on a grading system, and these grading experts were possibly the first example of panel training and maintenance in the literature. However, there was no mention of screening for sensory acuity, and experts checked their assessments against those of their colleagues or standard samples. Some of these grading methods are still used for tea, wine, and coffee (Kilcast 2010).
The first named discrimination testing method was published in 1936 by Sylvia Cover, who wanted to determine if the cooking temperature of roasts made the meat more or less tender (Cover 1936). The new method was referred to as “the paired‐eating method,” which was based on the name “paired‐feeding method,” which was used in animal husbandry. The paired comparison method, which Cover used, had been in use for many years in other disciplines, including psychology, statistics, mathematics, and economics, however, Cover was the first to apply it in the context of sensory science to test food (David 1963).
Cover’s paper on the assessment of meat tenderness is an interesting read, and the method she developed is now known as “the paired comparison.” This discrimination test is actually referred to as the first published method in sensory science. Cover presented the judges with two carefully selected samples, known as “paired bites,” in her pioneering discrimination testing method for meat tenderness assessment. To ensure the reliability of the testing, the cuts were taken from the left and right sides of the same animal, and the bite‐sized pieces were from the same muscle type. Despite the research having excellent sampling control, the use of three‐digit codes or balanced designs was yet to appear. Cover did not disclose how many judges were employed, nor whether they were screened or trained, although she conducted 261 paired comparisons over a period of two years. According to Cover, the advantages of using the paired‐eating method were its simplicity and the ability to directly compare samples. She used the binomial method to determine the statistical significance of her results but did not mention this as an advantage.
In 1939, Cover made several improvements to her method based on suggestions from colleagues, aiming to enhance its applicability to various aspects of food research (Cover 1940). Among the significant modifications was the alteration of the sample presentation order, which Cover determined by employing a deck of playing cards, effectively mitigating any potential bias introduced by her technician. To minimize the occurrence of expectation errors, Cover removed meat identification information from the sheet provided to the judges. In addition to the binomial method she had previously employed, Cover employed the Chi‐square method to analyze the data. Addressing the issue of judge selection, training, and the number of judges, Cover stated in her publication that no method had yet been devised to identify individuals who would serve as superior judges. Consequently, Cover recommended the involvement of more than two judges for each experiment, and for the majority of tests, she employed a panel of six judges. Each judge evaluated between eight and 11 pairs of the same two samples. Cover could not have anticipated that the analysis of replicated discrimination tests would remain a topic of contention even in contemporary times.
If the paired comparison method is considered to be the first sensory discrimination test in the field of food research, the second test is believed to be the triangle test, which was independently developed by two groups of researchers. The Seagram Quality Research Laboratory developed the test in 1941–1942 but did not publish the details until later (Peryam and Swartz 1950), while the Carlsberg Breweries Research Laboratory developed the test in 1946 (Bengtsson and Helm 1946; Helm and Trolle 1946). The 1946 papers refer to earlier publications that also discuss methodologies and statistics, although it is unclear if the triangle test was mentioned. Both groups of authors refer to the “triangular test” as having been in use for several years, suggesting its origin a few years earlier.
Carlsberg Breweries published two papers on the triangle test (Bengtsson and Helm 1946; Helm and Trolle 1946), which are noteworthy in a historical sense beyond discrimination testing. These papers contain interesting references to consumer testing, or “mass testing” as it was referred to, and include photographs and a consumer questionnaire with just two questions (six if personal information is included). The publications also describe the essential elements to consider before conducting a sensory study, which are now commonly taken for granted. It is challenging to imagine the difficulties faced by food scientists at that time when evaluating new products or changes in ingredients without such tools and advice.
This early version of the triangle test involved giving each judge three bottles of beer labelled with a number or letter, where two of the bottles contained the same beer and the third contained a different beer. The appearance of the bottles and beers was identical except for the identifying label. The tasters poured the beer into three glasses and were asked to identify “which two samples are identical?” The presentation design of the six possible A and B combinations was randomized across four replicate tests, and the judges worked independently in a room kept at 20°C. Additionally, judges were asked for their preference after the test and were informed whether their choice was correct or incorrect, both of which are no longer recommended. The statistical analysis was conducted using a table of values created by Bengtsson, who adapted the Chi‐square analysis for use with triangle tests. The judges were allowed to specify that they could not detect a difference, resulting in three possible answers for each test: the number correct, the number incorrect, and those who could not detect any difference.
Another difference between the early and modern versions of the test is that each judge participated in each test around 24 times, and there was no provision for replicated testing in the analysis. However, the authors aimed to select “expert” tasters and needed this type of data to determine each individual’s tasting ability.
The description of the triangle test as outlined by Peryam and Swartz in 1950 is more similar to the method employed today. It entailed presenting three samples to the judge, with two of them being identical and the third being different, and the judge was asked to identify the odd sample. However, there is one major difference to the test in use today, in that the control sample would always be presented twice, resulting in only three presentation designs in total. This is markedly different from the Bengtsson, Helm, and Trolle’s description of the test, who used all six presentation designs as we do today. The triangle test was also frequently used by the authors for determining preference, which is now avoided.
In its early days, the triangle test was referred to by various names, such as the Helm technique, the trio comparison, the triad, the triangular test, the odd sample method, the oddity (which understandably fell out of favor quickly), and the three‐glass test. The ISO standard was still referred to as the “triangular test” until the name triangle became officially adopted in the title in 2004. In 1948, Roessler and colleagues at the University of California developed the first table of critical values for the triangle test, which must have been a significant benefit to researchers at the time, given the absence of computers (Roessler et al. 1948).
The Seagram Quality Research Laboratory paper (Peryam and Swartz 1950) also describes two additional discrimination tests: the duo‐trio and the dual‐standard. These tests were likely developed in 1941–1942 alongside the triangle test. The duo‐trio involves presenting judges with three samples, one of which is labelled as the control and the other two coded: one sample is the test sample and the other a repeat of the control. The judge was asked to identify the sample that was different from the control. In the dual standard, four samples are presented in pairs, with the judge becoming familiar with the differences between the first pair before being presented with coded versions and asked to identify which sample is like each standard.
The difference‐preference test was developed in the 1940s (Dove 1947). This test was part of the “Subjective‐Objective Approach,” which aimed to emphasize the importance of subjective assessments in food testing. The test involved paired comparisons with an added preference question using a 10‐point scale. The author also listed requirements for the laboratory, sample preparation, and judges, including selecting judges based on vocabulary, experience, and ability to detect small differences. The paper also describes taste tests with animals instead of humans on products such as lettuce and cabbage.
In 1932, Arthur Fox discovered the taste anomaly with phenylthiocarbamide (PTC) in his famous “dust flying” experiment (Fox 1932). Harris and Kalmus (1949) discussed various methods to assess whether people were tasters or nontasters of PTC in an attempt to resolve conflicting findings. They proposed a test based on the method of limits, where the subject is presented with eight small glasses, four containing PTC and four not, and is asked to sort them into two groups. This test has been referred to as the Harris‐Kalmus test, the Harris‐Kalmus threshold procedure, the double tetrad, or the octad (Lawless and Heymann 2010). The method is similar to Fisher’s tea‐tasting experiment mentioned earlier in the chapter.
In the 1940s and 1950s, there was significant progress in sensory testing, especially in sensory discrimination tests, due to the focus on nutrition during the war years and interest in the development of new food products. In 1950, the US Bureau of Human Nutrition and Home Economics held a conference to gather information and make recommendations for future food testing, attended mainly by academics and research associations (Howgate 2015). The conference proceedings provide valuable insights into the difficulties of testing food using sensory methods, including discussions between David Peryam, Claude Hills, and Sylvia Cover (Dawson and Harris 1951). Lockhart (1951) proposed many potential sensory discrimination tests and suggested a useful table for test layouts, including M + N tests, which encompass over 40 tests for sensory discrimination testing (Bi 2015). In 1949, Wood recommended the tetrad test, which at the time involved presenting four samples and asking the subject to identify the samples as either A or B. Neither Wood, Lockhart, nor Peryam referred to the test as the tetrad, it was only later renamed by Renner and Romer (1973). Munson and Gardner (1950) created the ABX task, which involved presenting three samples and asking the subject to match the third sample to one of the first two. While the ABX task is not commonly used in sensory science, being mainly used in psycholinguistics and acoustic testing, it has potential for projects involving masking techniques (Greenaway 2017).
Statistical methods for analyzing discrimination tests were widely discussed in publications (Fisher 1935; Friedman 1937; Kendall 1938, 1954; Roessler et al. 1948; Lockhart 1951; Bradley 1953; Bliss 1960; Gridgeman 1960). Distinctions between trained panellists and untrained consumers were also debated (Platt 1937; Morse 1942; Bliss et al. 1943; Dove 1947), with Kiehl and Rhodes (1956) calling for more rigorous consumer testing. Kiehl notes the use of small numbers of people in “difference‐preference” methods and emphasizes the importance of not assuming expert preferences represent those of the general public. This area has been discussed more recently: see Ares and Varela (2017) and the subsequent comments for a very interesting discussion.
Interest in experimental design for sensory testing was also prominent, with publications discussing issues such as the number of samples assessed in a session, panel member selection, number of panellists required, sample presentation order, and the use of forms versus oral recordings (Platt 1937; Cartwright et al. 1952; Mason and Koch 1953; Hopkins 1954; Gridgeman 1955). Pfaffmann et al. (1954) introduced the “single stimulus” method, assessing one sample at a time: later called the A‐not A test. Davis and Hanson (1954) introduced the adapted triangle test and four‐sample test, which addressed not only whether there was a difference but also the intensity and direction of the difference.
The n‐alternative forced choice tests (e.g. n‐AFC: 2‐AFC, 3‐AFC, 4‐AFC, etc.) aimed to minimize response bias, i.e. differences in subjects’ criteria for determining differences. Blackwell (1953) suggested this type of approach instead of the method of limits for vision thresholds with paired samples, and Jones (1956) suggested using any number of blank samples with the stimulus material, e.g. A‐BBB (4‐AFC). Byer and Abrams (1953) used the 2‐AFC method (referred to as the “2‐sample test”) and compared it to the triangle test method for assessing beer. Although Dawson and Dochterman (1951
