TECHNIQUES FOR ANALYZING FOOD AROMA
CONTENTS 1 INTRODUCTION 1 1 1 INTRODUCTION AND OVERVIEW 1 1 1 1 DE NITION 1 1 1 2 MEASUREMENT 3 1 2 HISTORICAL LANDMARKS AND THE THREE CLASSES OF TEST METHODS 4 1 2 1 DIFFERENCE TESTING 5 1 2 2 DESCRIPTIVE ANALYSES 6 1 2 3 AFFECTIVE TESTING 7 1 2 4 THE CENTRAL DOGMA ANALYTIC VERSUS HEDONIC TESTS 8 1 3 APPLICATIONS WHY COLLECT SENSORY DATA 10 1 3 1 DIFFERENCES FROM MARKETING RESEARCH METHODS 13 1 3 2 DIFFERENCES FROM TRADITIONAL PRODUCT GRADING SYSTEMS 15 1 4 SUMMARY AND CONCLUSIONS 16 REFERENCES 17 2 PHYSIOLOGICAL AND PSYCHOLOGICAL FOUNDATIONS OF SENSORY FUNCTION 19 2 1 INTRODUCTION 19 2 2 CLASSICAL SENSORY TESTING AND PSYCHOPHYSICAL METHODS 20 2 2 1 EARLY PSYCHOPHYSICS 20 2 2 2 THE CLASSICAL PSYCHOPHYSICAL METHODS 21 2 2 3 SCALING AND MAGNITUDE ESTIMATION 23 2 2 4 CRITIQUES OF STEVENS 25 2 2 5 EMPIRICAL VERSUS THEORY DRIVEN FUNCTIONS 25 2 2 6 PARALLELS OF PSYCHOPHYSICS AND SENSORY EVALUATION 26 2 3 ANATOMY AND PHYSIOLOGY AND FUNCTIONS OF TASTE 27 2 3 1 ANATOMY AND PHYSIOLOGY 27 2 3 2 TASTE PERCEPTION QUALITIES 30 2 3 3 TASTE PERCEPTION ADAPTATION AND MIXTURE INTERACTIONS 30 2 3 4 INDIVIDUAL DIFFERENCES AND TASTE GENETICS 33 2 4 ANATOMY AND PHYSIOLOGY AND FUNCTIONS OF SMELL 34 2 4 1 ANATOMY AND CELLULAR FUNCTION 34 2 4 2 RETRONASAL SMELL 36 2 4 3 OLFACTORY SENSITIVITY AND SPECI C ANOSMIA 37 2 4 4 ODOR QUALITIES PRACTICAL SYSTEMS 38 2 4 5 FUNCTIONAL PROPERTIES ADAPTATION MIXTURE SUPPRESSION AND RELEASE 39 2 5 CHEMESTHESIS 41 2 5 1 QUALITIES OF CHEMESTHETIC EXPERIENCE 41 2 5 2 PHYSIOLOGICAL MECHANISMS OF CHEMESTHESIS 42 2 5 3 CHEMICAL HEAT 43 2 5 4 OTHER IRRITATIVE SENSATIONS AND CHEMICAL COOLING 44 2 5 5 ASTRINGENCY 45 2 5 6 METALLIC TASTE 46 2 6 MULTI MODAL SENSORY INTERACTIONS 47 2 6 1 TASTE AND ODOR INTERACTIONS 47 2 6 2 IRRITATION AND FLAVOR 49 2 6 3 COLOR FLAVOR INTERACTIONS 49 2 7 CONCLUSIONS 50 REFERENCES 50 3 PRINCIPLES OF GOOD PRACTICE 57 3 1 INTRODUCTION 57 3 2 THE SENSORY TESTING ENVIRONMENT 58 3 2 1 EVALUATION AREA 59 3 2 2 CLIMATE CONTROL 62 3 3 TEST PROTOCOL CONSIDERATIONS 63 3 3 1 SAMPLE SERVING PROCEDURES 63 3 3 2 SAMPLE SIZE 63 3 3 3 SAMPLE SERVING TEMPERATURES 64 3 3 4 SERVING CONTAINERS 64 3 3 5 CARRIERS 65 3 3 6 PALATE CLEANSING 65 3 3 7 SWALLOWING AND EXPECTORATION 66 3 3 8 INSTRUCTIONS TO PANELISTS 66 3 3 9 RANDOMIZATION AND BLIND LABELING 66 3 4 EXPERIMENTAL DESIGN 66 3 4 1 DESIGNING A STUDY 66 3 4 2 DESIGN AND TREATMENT STRUCTURES 69 3 5 PANELIST CONSIDERATIONS 72 3 5 1 INCENTIVES 72 3 5 2 USE OF HUMAN SUBJECTS 73 3 5 3 PANELIST RECRUITMENT 74 3 5 4 PANELIST SELECTION AND SCREENING 74 3 5 5 TRAINING OF PANELISTS 75 3 5 6 PANELIST PERFORMANCE ASSESSMENT 75 3 6 TABULATION AND ANALYSIS 75 3 6 1 DATA ENTRY SYSTEMS 75 3 7 CONCLUSION 76 REFERENCES 76 4 DISCRIMINATION TESTING 79 4 1 DISCRIMINATION TESTING 79 4 2 TYPES OF DISCRIMINATION TESTS 80 4 2 1 PAIRED COMPARISON TESTS 80 4 2 2 TRIANGLE TESTS 83 4 2 3 DUO TRIO TESTS 84 4 2 4 N ALTERNATIVE FORCED CHOICE N AFC METHODS 85 4 2 5 A NOT A TESTS 85 4 2 6 SORTING METHODS 87 4 2 7 THE ABX DISCRIMINATION TASK 88 4 2 8 DUAL STANDARD TEST 88 4 3 REPUTED STRENGTHS AND WEAKNESSES OF DISCRIMINATION TESTS 88 4 4 DATA ANALYSES 89 4 4 1 BINOMIAL DISTRIBUTIONS AND TABLES 89 4 4 2 THE ADJUSTED CHI SQUARE 2 TEST 90 4 4 3 THE NORMAL DISTRIBUTION AND THE Z TEST ON PROPORTION 90 4 5 ISSUES 92 4 5 1 THE POWER OF THE STATISTICAL TEST 92 4 5 2 REPLICATIONS 94 4 5 3 WARM UP EFFECTS 97 4 5 4 COMMON MISTAKES MADE IN THE INTERPRETATION OF DISCRIMINATION TESTS 97 APPENDIX A SIMPLE APPROACH TO HANDLING THE A NOT A AND SAME DIFFERENT TESTS 98 REFERENCES 99 5 SIMILARITY EQUIVALENCE TESTING AND DISCRIMINATION THEORY 101 5 1 INTRODUCTION 101 5 2 COMMON SENSE APPROACHES TO EQUIVALENCE 103 5 3 ESTIMATION OF SAMPLE SIZE AND TEST POWER 104 5 4 HOW BIG OF A DIFFERENCE IS IMPORTANT DISCRIMINATOR THEORY 105 5 5 TESTS FOR SIGNI CANT SIMILARITY 108 5 6 THE TWO ONE SIDED TEST APPROACH TOST AND INTERVAL TESTING 110 5 7 CLAIM SUBSTANTIATION 111 5 8 MODELS FOR DISCRIMINATION SIGNAL DETECTION THEORY 111 5 8 1 THE PROBLEM 112 5 8 2 EXPERIMENTAL SETUP 112 5 8 3 ASSUMPTIONS AND THEORY 113 5 8 4 AN EXAMPLE 114 5 8 5 A CONNECTION TO PAIRED COMPARISONS RESULTS THROUGH THE ROC CURVE 116 5 9 THURSTONIAN SCALING 116 5 9 1 THE THEORY AND FORMULAE 116 5 9 2 EXTENDING THURSTONE S MODEL TO OTHER CHOICE TESTS 118 5 10 EXTENSIONS OF THE THURSTONIAN METHODS R INDEX 119 5 10 1 SHORT CUT SIGNAL DETECTION METHODS 119 5 10 2 AN EXAMPLE 120 5 11 CONCLUSIONS 120 APPENDIX NON CENTRAL T TEST FOR EQUIVALENCE OF SCALED DATA 122 REFERENCES 122 6 MEASUREMENT OF SENSORY THRESHOLDS 125 6 1 INTRODUCTION THE THRESHOLD CONCEPT 125 6 2 TYPES OF THRESHOLDS DE NITIONS 127 6 3 PRACTICAL METHODS ASCENDING FORCED CHOICE 128 6 4 SUGGESTED METHOD FOR TASTE ODOR FLAVOR DETECTION THRESHOLDS 129 6 4 1 ASCENDING FORCED CHOICE METHOD OF LIMITS 129 6 4 2 PURPOSE OF THE TEST 129 6 4 3 PRELIMINARY STEPS 130 6 4 4 PROCEDURE 131 6 4 5 DATA ANALYSIS 131 6 4 6 ALTERNATIVE GRAPHICAL SOLUTION 131 6 4 7 PROCEDURAL CHOICES 133 6 5 CASE STUDY WORKED EXAMPLE 133 6 6 OTHER FORCED CHOICE METHODS 134 6 7 PROBIT ANALYSIS 136 6 8 SENSORY ADAPTATION SEQUENTIAL EFFECTS AND VARIABILITY 136 6 9 ALTERNATIVE METHODS RATED DIFFERENCE ADAPTIVE PROCEDURES SCALING 137 6 9 1 RATED DIFFERENCE FROM CONTROL 137 6 9 2 ADAPTIVE PROCEDURES 138 6 9 3 SCALING AS AN ALTERNATIVE MEASURE OF SENSITIVITY 140 6 10 DILUTION TO THRESHOLD MEASURES 140 6 10 1 ODOR UNITS AND GAS CHROMATOGRAPHY OLFACTOMETRY GCO 140 6 10 2 SCOVILLE UNITS 142 6 11 CONCLUSIONS 142 APPENDIX MTBE THRESHOLD DATA FOR WORKED EXAMPLE 143 REFERENCES 145 7 SCALING 149 7 1 INTRODUCTION 149 7 2 SOME THEORY 151 7 3 COMMON METHODS OF SCALING 152 7 3 1 CATEGORY SCALES 152 7 3 2 LINE SCALING 155 7 3 3 MAGNITUDE ESTIMATION 156 7 4 RECOMMENDED PRACTICE AND PRACTICAL GUIDELINES 158 7 4 1 RULE 1 PROVIDE SUF CIENT ALTERNATIVES 159 7 4 2 RULE 2 THE ATTRIBUTE MUST BE UNDERSTOOD 159 7 4 3 RULE 3 THE ANCHOR WORDS SHOULD MAKE SENSE 159 7 4 4 TO CALIBRATE OR NOT TO CALIBRATE 159 7 4 5 A WARNING GRADING AND SCORING ARE NOT SCALING 160 7 5 VARIATIONS OTHER SCALING TECHNIQUES 160 7 5 1 CROSS MODAL MATCHES AND VARIATIONS ON MAGNITUDE ESTIMATION 160 7 5 2 CATEGORY RATIO LABELED MAGNITUDE SCALES 162 7 5 3 ADJUSTABLE RATING TECHNIQUES RELATIVE SCALING 164 7 5 4 RANKING 165 7 5 5 INDIRECT SCALES 166 7 6 COMPARING METHODS WHAT IS A GOOD SCALE 167 7 7 ISSUES 168 7 7 1 DO PEOPLE MAKE RELATIVE JUDGMENTS SHOULD THEY SEE THEIR PREVIOUS RATINGS 168 7 7 2 SHOULD CATEGORY RATING SCALES BE ASSIGNED INTEGER NUMBERS IN DATA TABULATION ARE THEY INTERVAL SCALES 169 7 7 3 IS MAGNITUDE ESTIMATION A RATIO SCALE OR SIMPLY A SCALE WITH RATIO INSTRUCTIONS 169 7 7 4 WHAT IS A VALID SCALE 169 7 8 CONCLUSIONS 170 APPENDIX 1 DERIVATION OF THURSTONIAN SCALE VALUES FOR THE 9 POINT SCALE 171 APPENDIX 2 CONSTRUCTION OF LABELED MAGNITUDE SCALES 172 REFERENCES 174 8 TIME INTENSITY METHODS 179 8 1 INTRODUCTION 179 8 2 A BRIEF HISTORY 180 8 3 VARIATIONS ON THE METHOD 182 8 3 1 DISCRETE OR DISCONTINUOUS SAMPLING 182 8 3 2 CONTINUOUS TRACKING 183 8 3 3 TEMPORAL DOMINANCE TECHNIQUES 184 8 4 RECOMMENDED PROCEDURES 185 8 4 1 STEPS IN CONDUCTING A TIME INTENSITY STUDY 185 8 4 2 PROCEDURES 186 8 4 3 RECOMMENDED ANALYSIS 186 8 5 DATA ANALYSIS OPTIONS 187 8 5 1 GENERAL APPROACHES 187 8 5 2 METHODS TO CONSTRUCT OR DESCRIBE AVERAGE CURVES 188 8 5 3 CASE STUDY SIMPLE GEOMETRIC DESCRIPTION 189 8 5 4 ANALYSIS BY PRINCIPAL COMPONENTS 192 8 6 EXAMPLES AND APPLICATIONS 193 8 6 1 TASTE AND FLAVOR SENSATION TRACKING 193 8 6 2 TRIGEMINAL AND CHEMICAL TACTILE SENSATIONS 194 8 6 3 TASTE AND ODOR ADAPTATION 194 8 6 4 TEXTURE AND PHASE CHANGE 195 8 6 5 FLAVOR RELEASE 195 8 6 6 TEMPORAL ASPECTS OF HEDONICS 196 8 7 ISSUES 197 8 8 CONCLUSIONS 198 REFERENCES 198