Table Of ContentFOOD COLOUR AND APPEARANCE
To Jenny, Dickon, Charles, James and Matthew
FOOD COLOUR
AND APPEARANCE
JOHN B. HUTCHINGS
Co 1m worth , Bedford, UK, MK442LA
SPRINGER-SCIENCE+BUSINESS MEDIA, B.V.
First edition 1994
© 1994 Springer Science+Business Media Dordrecht
Originally published by Chapman & Ha1l in 1994
Softcover reprint ofthe hardcover Ist edition 1994
Typeset in 10/12 pt Times New Roman by the Universities Press (Be1fast)
Ltd, Belfast
ISBN 978-1-4613-5885-5 ISBN 978-1-4615-2123-5 (eBook)
DOI 10.1007/978-1-4615-2123-5
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PREFACE
Much of man's behaviour is controlled by appearance, but the
appearance of his food is of paramount importance to his health and
well-being. In day-to-day survival and marketing situations, we can
tell whether or not most foods are fit to eat from their optical
properties. Although vision and colour perception are the means by
which we appreciate our surroundings, visual acceptance depends on
more than just colour. It depends on total appearance.
In the recent past the food technologist has been under pressure to
increase his/her understanding of first, the behaviour of raw materials
under processing, and second, the behaviour and motivation of his/her
customers in a growing, more discriminating, and worldwide market.
The chapters which follow describe the philosophy of total ap
pearance, the factors comprising it, and its application to the food
industry. Included are: considerations of the evolutionary, historical,
and cultural aspects of food appearance; the physics and food
chemistry of colour and appearance; the principles of sensory ap
pearance assessment and appearance profile analysis, as well as
instrumental measurement; the interaction of product appearance,
control, and acceptance in the varied environments of the
laboratory, production line, supermarket, home and restaurant.
A broad examination has been made in an attempt to get into
perspective the importance of appearance to all sectors of the industry.
By including the principles of food appearance under one cover, the
treatment also aims to encourage interdisciplinary cross-fertilization of
approach and method among different parts of the industry.
vi Preface
This work provides a grounding in the science and methodology of
food appearance. It is a basic and reference text, suitable for those
scientists, technologists, designers, manufacturers, and product de
velopers in industry and academia whose concern is for the way foods
and food environments look. It will also serve as a text for students of
food science, technology, marketing, and for those concerned in any
way with food presentation and food appearance specification. The
message to take away is that total appearance in foods, as in all areas
of life, can be understood, described, quantified and optimized.
Many people contribute in many different ways to a work like this.
My involvement in the study of the science behind human behaviour,
a topic of never ending variety and fascination, has been actively
encouraged by Graham Evans and Peter Lillford of Unilever Research
Laboratory, Colworth House, Bedford. The friendship of many
members of that laboratory, the Colour Group (GB), and the
International Colour Association (AI C) , together with the discipline
these organizations have provided, have played no small part in my
upbringing. My grateful thanks must be recorded to all who have, in
one way or another, personally contributed to this upbringing and to
this volume. These include: David Wright, Margaret Halstead, Robert
Hunt (City University), John Mollon and David Hall (University of
Cambridge), Mike Pointer (Kodak), Allan Clark, Kathey Parkinson
and Peter Wilding (Colworth House), Douglas MacDougall (Reading
University), Peter D'A gostino (Barnfield College), Howard Mos
kowitz (Moskowitz/Jacobs Inc), Fred W Billmeyer Jr (Consultant),
Ralph Brocklebank (Geothean Science Foundation), Roberto Lozano
(INTI Argentina), Jan Walraven (TNO Institute of Perception,
Soesterberg), Mahon Patel (Pointing), Ann Mundy (Bass Brewers),
Heather Crosby (John Lewis), Barry Truman (Sainsbury), Andrew
Usher (D F Anstead), and not forgetting my family.
John B Hutchings
6 Queens Road
Colmworth
Bedford MK44 2LA UK
CONTENTS
Preface v
Chapter 1 Food Colour and Appearance in Perspective 1
The Evolution of Food Colour 2
The Physiological Role of Pigments 5
Food Colour and the Use of Food Colorants 5
Rules Governing Other Appearance Attributes 12
The Relative Importance of Appearance, Flavour and Texture as
Product Attributes 14
Colour in Food Packaging 17
Food Colour in the English Language 22
References . 27
Chapter 2 The Philosophy of Total Appearance 30
The Place of Appearance in Total Perception 31
Factors Affecting Total Appearance 32
Light Source Properties 34
Object Properties 35
Receptor Mechanisms 35
Inherited and Learned Responses: Cultural anthropology and
food appearance; Colour and appearance associations and
symbolisms . 36
Immediate Environmental Factors . 45
Product Images . 47
Total Appearance Philosophy and the Gestalt 49
viii Contents
Mathematical Calculation of Consumer Images 51
Need, Desirability and Market Stimulus Value 52
Connotative Meanings of Objects 53
Acceptance . 54
Quality. 55
Total Appearance as a Science 56
References . 57
Chapter 3 Light and Interaction with Materials 61
Light and Lighting 61
Black Body Radiators 61
Standard Illuminants . 63
Practical Light Sources 64
Absorption and Scattering of Light. 70
Absorption . 70
Scattering 71
The Kubelka-Munk Theory for Multiple Scattering 77
Correcting for the Regularly Reflected Component 81
Delayed Light Emission 82
References . 83
Chapter 4 Vision . 8S
The Eye 85
Colour Perception 88
Basic Colour Attributes 90
Colour Constancy and Chromatic Adaptation 91
Contrast Phenomena . 94
Colour Memory . 96
Colour Harmony. 98
Colour Vision Deficiency . 100
References . 102
Chapter 5 Sensory Evaluation of Appearance--
Methodology . 104
Panel Selection, Screening and Training 107
Factors Affecting Panel Performance 109
The Halo Effect: Types of halo effect; Psychophysical relation-
ships between colour and flavour . 111
Expert Tasters as Predictors of Consumer Response. . 120
Contents ix
Physical Requirements for Food Appearance Assessment. 121
Lighting for Appearance Assessment 123
Types of Sensory Test 125
Discrimination and Descriptive Testing . 125
Affective (Preference and Acceptance) Testing 128
Statistics and Mathematics in Appearance Sensory Testing 130
References . 135
Chapter 6 Appearance Profile Analysis and Sensory Scales. 142
Colour and Appearance Memory Descriptors and Scales . 144
Visual Structure: Produce sorting; Product definition; Defini-
tions of structural defects. 144
Visual Texture 157
Visual Flavour 157
Translucency 158
Gloss 159
Colour. 160
Colour Uniformity 173
Examples of Appearance Profile Analysis 175
Appearance Comparative Scales 180
Colour Atlases: Royal Horticultural Society charts; The Mun-
sell system and atlas; The Natural Colour System (NCS); An
atlas for the foods and allied industries . 180
Scales and Anchors for Specific Foods 187
References . 192
Chapter 7 Instrumental Specification . . 199
Colour Measurement . 199
Tristimulus and Spectrophotometric Measurement 207
Instrumental Factors. 209
Dominant Wavelength and Purity Calculations 211
Discrimination of Colour Attributes 213
Properties of the Chromaticity Diagram 215
Uniform Chromaticity Space and Uniform Colour Scales 217
Colour Difference Calculation . 223
Measurements and Perceptual Correlates 223
Subtractive Colorimetry 225
Metamerism. 225
Fluorescence 227
x Contents
Translucency 227
Gloss 230
Colour Measuring Instruments used for Foods 232
References . 235
Chapter 8 Colour Specification of Food . 238
The Sample and the Instrument 239
Colour Measurement of Opaque Samples 243
Colour Measurement of Transparent Samples 245
Colour Measurement of Translucent Samples 246
Understanding Sensory Quality 249
Visualizing Tristimulus Coordinates 252
The Three Dimensional Nature of Colour Change 255
Occurrence of Multimodal Populations . 257
Confusion Caused by Too Wide a Range of Samples . 260
The Colour of Translucent Materials 261
Relationships Between Hedonic Assessments and Instrumental
Measurements 264
Use of Colour Difference Equations 265
Understanding Process Materials-Quality Determination and
Control . 266
Isolating the Most Sensitive Tristimulus Dimension: Control
systems based on one dimension; Control systems based on two
dimensions; Control systems based on three dimensions. 268
Measurements made at Specific Wavelengths 274
Quality Control Methods Which Aim to Reproduce Estab
lished Visual Scales . 276
Changes Occurring in Visual versus Instrumental Relationships 278
Metamerism. 280
Transmitted Light Measurements . 281
Colour Sorting and Monitoring by Continuous Colorimetry 284
Understanding Processing. 288
Effect of Processing on Colour 288
Prediction of the Effect of Processing on Product Colour 291
Measurement of Browning 293
Mathematical Modelling: Empirical Modelling; Reaction kinet-
ics . 296
Understanding Chemistry. 308
Using Reflectance Measurements to Predict Pigment Content:
The tristimulus approach; The spectral approach. 308
Pigment Behaviour 315
References . 318
Description:Much of man's behaviour is controlled by appearance, but the appearance of his food is of paramount importance to his health and well-being. In day-to-day survival and marketing situations, we can tell whether or not most foods are fit to eat from their optical properties. Although vision and colour
