Sensory Evaluation of Food Principles and Practices

603 Pages·2010·9.974 MB·English

by  Lawless, Harry T;Heymann, Hildegarde

Food Science Text Series
The Food Science Text Series provides faculty with the leading teaching tools. The
Editorial Board has outlined the most appropriate and complete content for each
foodsciencecourseinatypicalfoodscienceprogramandhasidentifiedtextbooksof
thehighestquality,writtenbytheleadingfoodscienceeducators.
SeriesEditor
DennisR.Heldman
EditorialBoard
David A. Golden, Ph.D., Professor of Food Microbiology, Department of Food
ScienceandTechnology,UniversityofTennessee
Richard W. Hartel, Professor of Food Engineering, Department of Food Science,
UniversityofWisconsin
Hildegarde Heymann, Professor of Food Sensory Science, Department of Food
ScienceandTechnology,UniversityofCalifornia-Davis
Joseph H. Hotchkiss, Professor, Institute of Food Science and Institute for
Comparative and Environmental Toxicology, and Chair, Food Science Department,
CornellUniversity
MichaelG.Johnson,Ph.D.,ProfessorofFoodSafetyandMicrobiology,Department
ofFoodScience,UniversityofArkansas
Joseph Montecalvo, Jr., Professor, Department of Food Science and Nutrition,
CaliforniaPolytechnicandStateUniversity-SanLuisObispo
S. Suzanne Nielsen, Professor and Chair, Department of Food Science, Purdue
University
Juan L. Silva, Professor, Department of Food Science, Nutrition and Health
Promotion,MississippiStateUniversity
Forfurthervolumes:
http://www.springer.com/series/5999
·
Harry T. Lawless Hildegarde
Heymann
Sensory Evaluation
of Food
Principles and Practices
Second Edition
123
HarryT.Lawless HildegardeHeymann
DepartmentofFoodScience DepartmentofViticultureandEnology
CornellUniversity UniversityofCalifornia–Davis
StockingHall,Room106 2003RMISensoryBuilding
14853Ithaca Davis95616
NY,USA CA,USA
[email protected] [email protected]
ISSN1572-0330
ISBN978-1-4419-6487-8 e-ISBN978-1-4419-6488-5
DOI10.1007/978-1-4419-6488-5
SpringerNewYorkDordrechtHeidelbergLondon
LibraryofCongressControlNumber:2010932599
©SpringerScience+BusinessMedia,LLC2010
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Preface
Thefieldofsensorysciencehasgrownexponentiallysincethepublicationofthepre-
viousversionofthiswork.FifteenyearsagothejournalFoodQualityandPreference
wasfairlynew.Nowitholdsaneminentpositionasavenueforresearchonsensory
test methods (among many other topics). Hundreds of articles relevant to sensory
testing have appeared in that and in other journals such as the Journal of Sensory
Studies.Knowledgeoftheintricatecellularprocessesinchemoreception,aswellas
theirgeneticbasis,hasundergonenothinglessthanarevolution,culminatinginthe
awardoftheNobelPrizetoBuckandAxelin2004fortheirdiscoveryoftheolfactory
receptorgenesuperfamily.Advancesinstatisticalmethodologyhaveacceleratedas
well.Sensometricsmeetingsarenowvigorousandwell-attendedannualevents.Ideas
likeThurstonianmodelingwerenotwidelyembraced15yearsago,butnowseemto
bepartoftheeverydaythoughtprocessofmanysensoryscientists.
And yet, some things stay the same. Sensory testing will always involve human
participants. Humans are tough measuring instruments to work with. They come
withvaryingdegreesofacumen,training,experiences,differinggeneticequipment,
sensory capabilities, and of course, different preferences. Human foibles and their
associated error variance will continue to place a limitation on sensory tests and
actionableresults.Reducing,controlling,partitioning,andexplainingerrorvariance
are all at the heart of good test methods and practices. Understanding the product–
personinterfacewillalwaysbethegoalofsensoryscience.Noamountofelaborate
statistical maneuvering will save a bad study or render the results somehow useful
andvalid.Althoughmethodscontinuetoevolve,appreciationofthecoreprinciples
ofthefieldisthekeytoeffectiveapplicationofsensorytestmethods.
The notion that one can write a book that is both comprehensive and suitable as
anintroductorytextwasadauntingchallengeforus.Somemaysaythatwemissed
the mark on this or that topic, that it was either too superficially treated or too in
depthfortheirstudents.Perhapswehavetriedtodotheimpossible.Nonethelessthe
demand for a comprehensive text that would serve as a resource for practitioners is
demonstratedbythesuccessofthefirstedition.Itswidespreadadoptionasauniver-
sityleveltextshowsthatmanyinstructorsfeltthatitcouldbeusedappropriatelyfor
afirstcourseinsensoryevaluation.
This book has been expanded somewhat to reflect the advances in methodolo-
gies, theory, and analysis that have transpired in the last 15 years. The chapters are
now divided into numbered sections. This may be of assistance to educators who
maywishtoassignonlycertaincriticalsectionstobeginningstudents.Muchofthe
organization of key chapters has been done with this in mind and in some of the
v
vi Preface
opening sections; instructors will find suggestions about which sections are key for
fundamentalunderstandingofthattopicormethod.Inmanychapterswehavegone
out on a limb and specified a “recommended procedure.” In cases where there are
multiple options for procedure or analysis, we usually chose a simple solution over
one that is more complex. Because we are educators, this seemed the appropriate
path.
Note that there are two kinds of appendices in this book. The major statistical
methods are introduced with worked examples in Appendices A–E, as in the previ-
ousedition.Somemainchaptersalsohaveappendedmaterialsthatwefeltwerenot
criticaltounderstandingthemaintopic,butmightbeofinteresttoadvancedstudents,
statisticians,orexperienced practitioners.Wecontinue togive referencecitationsat
theendofeverychapter,ratherthaninonebiglistattheend.Statisticaltableshave
beenadded,mostnotablythediscriminationtablesthatmaynowbefoundbothinthe
AppendixandinChapter4itself.
One may question whether textbooks themselves are an outdated method for
information retrieval. We feel this acutely because we recognize that a textbook is
necessarily retrospective and is only one snapshot in time of a field that may be
evolvingrapidly.Studentsandpractitionersalikemayfindthatreferencetoupdated
websites,wikis,andsuchwillprovideadditionalinformationandnewanddifferent
perspectives.Weencouragesuchinvestigation.Textbooks,likeautomobiles,havean
element of built-in obsolescence. Also textbooks, like other printed books, are lin-
ear in nature, but the mind works by linking ideas. Hyperlinked resources such as
websitesandwikiswilllikelycontinuetoproveuseful.
Weaskyourpatienceandtoleranceformaterialsandcitationsthatwehaveleftout
thatyoumightfeelareimportant.Werecognizethattherearelegitimatedifferencesof
opinionandphilosophyabouttheentireareaofsensoryevaluationmethods.Wehave
attemptedtoprovideabalancedandimpartialviewbasedonourpracticalexperience.
Anyerrorsoffact,errorstypographical,orerrorsincitationareourownfault.Webeg
yourunderstandingandpatienceandwelcomeyourcorrectionsandcomments.
We could not have written this book without the assistance and support of many
people. WewouldliketothankKathy Dernoga forproviding apre-publication ver-
sion of the JAR scale ASTM manual as well as the authors of the ASTM JAR
manualLoriRothmanandMerryJoParker.Additionally,MarySchraidtofPeryam
andKrollprovidedupdatedexamplesofaconsumertestscreeningquestionnaireand
field study questionnaires. Thank you Mary. We thank John Hayes, Jeff Kroll, Tom
Carr,DannyEnnis,andJianBiforsupplyingadditionalliterature,software,andsta-
tisticaltables.GernotHoffmanngraciouslyprovidedgraphicsforChapter12.Thank
youDr.Hoffmann.WewouldliketothankWendyParrandJamesGreenforprovid-
ingsomegraphicsforChapter10.Additionally,GregHirsonprovidedsupportwith
R-Graphics. Thank you, Greg. Additionally, we want to thank the following peo-
plefortheirwillingness todiscussthebook inprogress andformaking veryuseful
suggestions:MichaelNestrud,SusanCuppett,EdanLev-Ari,ArmandCardello,Marj
Albright,DavidStevens,RichardPopper,andGregHirson.JohnHornehadalsobeen
very helpful in the previous edition, thank you John. Proofreading and editing sug-
gestions were contributed by Kathy Chapman, Gene Lovelace, Mike Nestrud, and
MargeLawless.
Although not directly involved with this edition of the book we would also like
to thank our teachers and influential mentors—without them we would be very dif-
ferent scientists, namely Trygg Engen, William S. Cain, Linda Bartoshuk, David
Preface vii
Peryam, David Stevens, Herb Meiselman, Elaine Skinner, Howard Schutz, Howard
Moskowitz, Rose Marie Pangborn, Beverley Kroll, W. Frank Shipe, Lawrence E.
Marks, Joseph C. Stevens, Arye Dethmers, Barbara Klein, Ann Noble, Harold
Hedrick,WilliamCStringer,RogerBoulton,KayMcMath,JoelvanWyk,andRoger
Mitchell.
Ithaca,NewYork HarryT.Lawless
Davis,California HildegardeHeymann
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 IntroductionandOverview . . . . . . . . . . . . . . . . . . . 1
1.1.1 Definition . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.2 Measurement . . . . . . . . . . . . . . . . . . . . . 3
1.2 HistoricalLandmarksandtheThreeClasses
ofTestMethods . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.1 DifferenceTesting . . . . . . . . . . . . . . . . . . . 5
1.2.2 DescriptiveAnalyses . . . . . . . . . . . . . . . . . 6
1.2.3 AffectiveTesting . . . . . . . . . . . . . . . . . . . 7
1.2.4 TheCentralDogma—AnalyticVersus
HedonicTests . . . . . . . . . . . . . . . . . . . . . 8
1.3 Applications:WhyCollectSensoryData? . . . . . . . . . . . 10
1.3.1 DifferencesfromMarketingResearchMethods . . . 13
1.3.2 DifferencesfromTraditionalProduct
GradingSystems . . . . . . . . . . . . . . . . . . . 15
1.4 SummaryandConclusions . . . . . . . . . . . . . . . . . . . 16
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2 PhysiologicalandPsychologicalFoundations
ofSensoryFunction . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2 ClassicalSensoryTestingandPsychophysicalMethods . . . . 20
2.2.1 EarlyPsychophysics . . . . . . . . . . . . . . . . . 20
2.2.2 TheClassicalPsychophysicalMethods . . . . . . . . 21
2.2.3 ScalingandMagnitudeEstimation . . . . . . . . . . 23
2.2.4 CritiquesofStevens . . . . . . . . . . . . . . . . . . 25
2.2.5 EmpiricalVersusTheory-DrivenFunctions . . . . . 25
2.2.6 ParallelsofPsychophysicsandSensory
Evaluation . . . . . . . . . . . . . . . . . . . . . . . 26
2.3 AnatomyandPhysiologyandFunctionsofTaste . . . . . . . . 27
2.3.1 AnatomyandPhysiology . . . . . . . . . . . . . . . 27
2.3.2 TastePerception:Qualities . . . . . . . . . . . . . . 30
2.3.3 TastePerception:AdaptationandMixture
Interactions . . . . . . . . . . . . . . . . . . . . . . 30
2.3.4 IndividualDifferencesandTasteGenetics . . . . . . 33
2.4 AnatomyandPhysiologyandFunctionsofSmell. . . . . . . . 34
2.4.1 AnatomyandCellularFunction . . . . . . . . . . . . 34
ix
x Contents
2.4.2 RetronasalSmell . . . . . . . . . . . . . . . . . . . 36
2.4.3 OlfactorySensitivityandSpecificAnosmia . . . . . 37
2.4.4 OdorQualities:PracticalSystems . . . . . . . . . . 38
2.4.5 FunctionalProperties:Adaptation,Mixture
Suppression,andRelease . . . . . . . . . . . . . . . 39
2.5 Chemesthesis. . . . . . . . . . . . . . . . . . . . . . . . . . . 41
2.5.1 QualitiesofChemestheticExperience . . . . . . . . 41
2.5.2 PhysiologicalMechanismsofChemesthesis . . . . . 42
2.5.3 Chemical“Heat” . . . . . . . . . . . . . . . . . . . 43
2.5.4 OtherIrritativeSensationsandChemical
Cooling . . . . . . . . . . . . . . . . . . . . . . . . 44
2.5.5 Astringency . . . . . . . . . . . . . . . . . . . . . . 45
2.5.6 MetallicTaste . . . . . . . . . . . . . . . . . . . . . 46
2.6 Multi-modalSensoryInteractions . . . . . . . . . . . . . . . . 47
2.6.1 TasteandOdorInteractions . . . . . . . . . . . . . . 47
2.6.2 IrritationandFlavor . . . . . . . . . . . . . . . . . . 49
2.6.3 Color–FlavorInteractions . . . . . . . . . . . . . . . 49
2.7 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
3 PrinciplesofGoodPractice . . . . . . . . . . . . . . . . . . . . . . . 57
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
3.2 TheSensoryTestingEnvironment . . . . . . . . . . . . . . . . 58
3.2.1 EvaluationArea . . . . . . . . . . . . . . . . . . . . 59
3.2.2 ClimateControl . . . . . . . . . . . . . . . . . . . . 62
3.3 TestProtocolConsiderations . . . . . . . . . . . . . . . . . . 63
3.3.1 SampleServingProcedures . . . . . . . . . . . . . . 63
3.3.2 SampleSize . . . . . . . . . . . . . . . . . . . . . . 63
3.3.3 SampleServingTemperatures . . . . . . . . . . . . 64
3.3.4 ServingContainers . . . . . . . . . . . . . . . . . . 64
3.3.5 Carriers . . . . . . . . . . . . . . . . . . . . . . . . 65
3.3.6 PalateCleansing . . . . . . . . . . . . . . . . . . . . 65
3.3.7 SwallowingandExpectoration . . . . . . . . . . . . 66
3.3.8 InstructionstoPanelists . . . . . . . . . . . . . . . . 66
3.3.9 RandomizationandBlindLabeling . . . . . . . . . . 66
3.4 ExperimentalDesign. . . . . . . . . . . . . . . . . . . . . . . 66
3.4.1 DesigningaStudy . . . . . . . . . . . . . . . . . . . 66
3.4.2 DesignandTreatmentStructures . . . . . . . . . . . 69
3.5 PanelistConsiderations . . . . . . . . . . . . . . . . . . . . . 72
3.5.1 Incentives . . . . . . . . . . . . . . . . . . . . . . . 72
3.5.2 UseofHumanSubjects . . . . . . . . . . . . . . . . 73
3.5.3 PanelistRecruitment . . . . . . . . . . . . . . . . . 74
3.5.4 PanelistSelectionandScreening . . . . . . . . . . . 74
3.5.5 TrainingofPanelists . . . . . . . . . . . . . . . . . 75
3.5.6 PanelistPerformanceAssessment. . . . . . . . . . . 75
3.6 TabulationandAnalysis . . . . . . . . . . . . . . . . . . . . . 75
3.6.1 DataEntrySystems . . . . . . . . . . . . . . . . . . 75
3.7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
Contents xi
4 DiscriminationTesting . . . . . . . . . . . . . . . . . . . . . . . . . 79
4.1 DiscriminationTesting . . . . . . . . . . . . . . . . . . . . . . 79
4.2 TypesofDiscriminationTests . . . . . . . . . . . . . . . . . . 80
4.2.1 PairedComparisonTests . . . . . . . . . . . . . . . 80
4.2.2 TriangleTests . . . . . . . . . . . . . . . . . . . . . 83
4.2.3 Duo–TrioTests . . . . . . . . . . . . . . . . . . . . 84
4.2.4 n-AlternativeForcedChoice(n-AFC)Methods . . . 85
4.2.5 A-Not-Atests . . . . . . . . . . . . . . . . . . . . . 85
4.2.6 SortingMethods . . . . . . . . . . . . . . . . . . . . 87
4.2.7 TheABXDiscriminationTask . . . . . . . . . . . . 88
4.2.8 Dual-StandardTest . . . . . . . . . . . . . . . . . . 88
4.3 ReputedStrengthsandWeaknessesofDiscrimination
Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
4.4 DataAnalyses . . . . . . . . . . . . . . . . . . . . . . . . . . 89
4.4.1 BinomialDistributionsandTables . . . . . . . . . . 89
4.4.2 TheAdjustedChi-Square(χ2)Test . . . . . . . . . . 90
4.4.3 TheNormalDistributionandtheZ-Test
onProportion . . . . . . . . . . . . . . . . . . . . . 90
4.5 Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
4.5.1 ThePoweroftheStatisticalTest . . . . . . . . . . . 92
4.5.2 Replications . . . . . . . . . . . . . . . . . . . . . . 94
4.5.3 Warm-UpEffects . . . . . . . . . . . . . . . . . . . 97
4.5.4 CommonMistakesMadeintheInterpretation
ofDiscriminationTests . . . . . . . . . . . . . . . . 97
Appendix:ASimpleApproachtoHandlingtheA,Not-A,
andSame/DifferentTests . . . . . . . . . . . . . . . . . . . . 98
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
5 Similarity,EquivalenceTesting,andDiscriminationTheory . . . . 101
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
5.2 CommonSenseApproachestoEquivalence . . . . . . . . . . 103
5.3 EstimationofSampleSizeandTestPower . . . . . . . . . . . 104
5.4 HowBigofaDifferenceIsImportant?
DiscriminatorTheory . . . . . . . . . . . . . . . . . . . . . . 105
5.5 TestsforSignificantSimilarity . . . . . . . . . . . . . . . . . 108
5.6 TheTwoOne-SidedTestApproach(TOST)
andIntervalTesting . . . . . . . . . . . . . . . . . . . . . . . 110
5.7 ClaimSubstantiation . . . . . . . . . . . . . . . . . . . . . . . 111
5.8 ModelsforDiscrimination:SignalDetectionTheory . . . . . . 111
5.8.1 TheProblem . . . . . . . . . . . . . . . . . . . . . . 112
5.8.2 ExperimentalSetup . . . . . . . . . . . . . . . . . . 112
5.8.3 AssumptionsandTheory . . . . . . . . . . . . . . . 113
5.8.4 AnExample . . . . . . . . . . . . . . . . . . . . . . 114
5.8.5 AConnectiontoPairedComparisonsResults
ThroughtheROCCurve . . . . . . . . . . . . . . . 116
5.9 ThurstonianScaling . . . . . . . . . . . . . . . . . . . . . . . 116
5.9.1 TheTheoryandFormulae. . . . . . . . . . . . . . . 116
5.9.2 ExtendingThurstone’sModeltoOther
ChoiceTests . . . . . . . . . . . . . . . . . . . . . . 118