Principles of Sensory Evaluation of Food

606 Pages·1965·11.329 MB·English

by  Maynard A. Amerine, Rose Marie Pangborn, Edward B. Roessler

FOOD SCIENCE AND TECHNOLOGY
A Scries of Monographs
Edited by
M. L. ANSON C. O. CHICHESTER
New York, New York University of California
Davis, California
E. M. MRAK
University of California G. F. STEWART
Davis, California University of California
Davis, California
1. Maynard A. Amerine, Rose Marie Pangborn, and Edward B. Roessler, PRINCIPLES
OF SENSORY EVALUATION OF FOOD. 1965
C. R. Stumbo, THERMOBACTERIOLOGY IN FOOD PROCESSING (in preparation)
PRINCIPLES OF
SENSORY EVALUATION
OF FOOD
Toy
Maynard A. Amcrinc
Rose Mark Panglorn
Edward B. Roesslcr
DEPARTMENTS OF VITICULTURE AND ENOLOGY,
FOOD SCIENCE AND TECHNOLOGY, AND MATHEMATICS,
UNIVERSITY OF CALIFORNIA,
DAVIS, CALIFORNIA
1965
ACADEMIC PRESS New York and London
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Preface
Food science deals with the multitude of problems involved in pro-
viding food for human consumption. It includes the entire process from
harvesting to serving. Investigations on the problems of food science
involve biochemistry, microbiology, genetics, plant physiology, and other
basic sciences, as well as engineering, horticulture, animal science, and
other applied sciences. The research emphasis in the food industry has
been primarily on economical preparation and distribution of safe and
nutritious foods. Universities and experiment stations throughout the
world have concerned themselves mainly with studies on chemical and
nutritive composition, microbiological control, processing, and the func-
tional properties of foodstuffs.
World War II focused attention upon another aspect of food science:
that foods were sometimes rejected by the potential consumer, no matter
how sound and nutritious they were. Furthermore, modern technology
gradually changed the traditional methods of food preparation, and
new and cheaper methods of production, storage, and distribution fre-
quently altered the sensory appeal of foods. These developments em-
phasized the growing need for research in a previously neglected area
—the sensory analysis of food. A review of food literature since 1940
reveals the rapid growth of this aspect of food science. It was thus
natural that, in 1957, the University of California at Davis instituted
an upper-division course intended for food majors in the analysis of
foods by sensory methods. The present text is an outgrowth of that
course.
Our philosophy has been that sound methodology for the sensory
analysis of foods rests on a thorough knowledge of sensory physiology
and an understanding of the psychology of perception. Essential in
addition is careful statistical design and analyses of the data. Finally,
new understanding of sensory judgment is to be sought through correla-
tion with physical and chemical data.
This text therefore includes chapters on the physiology and psy-
chology of the senses, a consideration of the present status of method-
ology, and appropriate statistical analyses of the results. The problems
of measuring consumer acceptance are also discussed. Finally, we in-
clude a brief treatment of the relationship between sensory character-
istics and various physical and chemical properties of foods. It is our
belief that objective tests will someday replace many of the present
subjective methods used in food science. In the final analysis, however,
food acceptance and preference depend on human sensory responses,
so it is imperative that tests employing human subjects continue.
We wish to thank, especially, Mrs. Elly Hinreiner Platou and Mrs.
v
vi PREFACE
Marion Simone Kunze for their help in organizing the course and in
reviewing the literature for this text. Appreciation is extended to Pro-
fessor F. N. Jones, University of California, Los Angeles; Dr. B. P.
Halpern, State University of New York; Dr. Herbert Stone, Stanford
Research Institute; Dr. Mildred Boggs, Western Regional Research Lab-
oratory; and Professors H. W. Berg, W. F. Dukes, P. W. M. John, G. F.
Stewart, and J. R. Whitaker, University of California, Davis, for advice
on particular chapters. The helpful suggestions of our colleagues, Dr.
M. H. Woskow, Mr. C. S. Ough, and Mr. Frank Winter, are gratefully
acknowledged. Needless to say, any errors are the responsibility of the
authors. We shall, of course, welcome any suggestions and corrections
from the readers of the text. We hope this book will be of use in the
training of food technologists in colleges and universities and for those
engaged in research on problems of the sensory evaluation of food
in university, government, and industrial laboratories. In view of the
many unsolved problems, many of which we have indicated, we also
hope that it will stimulate further research.
MAYNARD A. AMERINE
ROSE MARIE PANGBORN
EDWARD B. ROESSLER
Davis, California
August, 1965
Chapter 1
Sensory Evaluation Problems of the Food Industry
The most primitive animals develop likes and dislikes for food, with
many species displaying well-known predilections for one food over an-
other. Although Paleolithic man, in his never-ending quest for food, had
little opportunity to make fine quality distinctions, he obviously rejected
certain foods altogether and consumed others only in time of dire need.
The idea of improving flavor probably did not occur to early man until
he accidentally discovered the art of roasting. Further changes in eating
habits were brought about when Neolithic man planted cereals, domes-
ticated animals, irrigated fertile land, and settled in villages. As food
became abundant, society differentiated itself into producers, artisans,
rulers, warriors, priests, etc. All had some leisure time and some had a
good deal. Flavor distinctions and food preferences developed rapidly,
especially along class or status lines (see Stewart et al., 1965).
Many of our present-day food taboos and food habits undoubtedly
developed during the Neolithic period (Simoons, 1961). Some were
based on clan distinctions whereas others probably arose from con-
flicts between the nomadic way of life as compared to that of settled
communities. The prejudice of nomadic peoples against pork is one
example. Although the prophet Mohammed preached that pork was
dangerous to eat, Simoons believes there was an economic basis also:
the conflict between nomadic tribes, which could not raise pork, and
settled communities, which could. A few of the taboos may have had
a cultural or religious origin as a basis for separating the tribe or social
unit from the neighbors. According to Simoons, the Moslem prohibition
of alcoholic beverages was most likely due to a desire to distinguish the
new religion from the alcohol-drinking Christians.
I. Early History
It is not fully realized how often the senses of taste and smell have
influenced the history of human behavior. Henning (1924) listed a wide
1
2 1. SENSORY EVALUATION PROBLEMS OF THE FOOD INDUSTRY
variety of odorous materials that were important to the Egyptians, in-
cluding myrrh, cedar oil, asphalt, resin, cardamon, balsam, iris, and
turpentine. That the Jews were very conscious of odor is indicated by
the number of references to odorous materials in the Bible. Incense was
common, and Moses was given a recipe for one (Exodus 30, 34): equal
parts of stacte, sweet spices, galbanum, onycha, and frankincense. Ara-
bians and Persians also used large amounts of odorous materials for
incense and perfumes. Association of odorous materials with religious
and sexual practices was undoubtedly important, as was propitiation of
the gods with expensive, rare, and pleasant things. Even today, religious
use of incense to engender a worshipful frame of mind is not unknown.
Flowers at funerals may have a similar olfactory-religious origin.
In India, sandalwood oil was used as an odorous substance in the 9th
century. Spices, butter, oil, lemon, and other materials were used in
cooking. When the Portuguese and British came to India they found a
well-developed spice industry. The discovery of America was indirectly
related to Europe's demand for oriental odorous material for food
flavoring and for cosmetics. Chinese emperors had such a fondness for
aromatic foods that the Sung Dynasty (960-1279) exacted tribute of
odorous foods from south China. A whole cult of floral esthetics de-
veloped in Japan, and the formal tea-drinking ceremony which de-
veloped from this has sensory as well as esthetic aspects. Greek
mythology is filled with the religious use of spices, incense, and per-
fumes. Roses, violets, and other flowers were assiduously cultivated for
the esthetic olfactory pleasures which they engendered. The Romans
made perfumes a world-wide industry. This industry reached its heyday
during the Renaissance, when Italian and Spanish perfumes were im-
ported to France. Bienfang (1946) and Bedichek (1960) described
how the sense of smell has been used in literature.
II. Modern Sensory Problems
A. ODOR
Because of the greater range of olfactory responses, there are prob-
ably more odor than taste problems in the food industry. Some modern
industrial odor problems are of great concern, such as control of waste-
disposal odors in food plants that process protein products. The develop-
ment of desirable odors in fruits, wines, and cheeses with age is well
known, but a wide variety of undesirable odors are also associated with
the storage of food. Undesirable odors and textures may develop in food
when inadequate packaging material or improper storage temperatures
are used. There are also persistent odor problems associated with the use
II. Modern Sensory Problems 3
of preservatives in foods (sulfur dioxide, benzoic acid, sorbates, etc.)
and with the field use of various insecticides and fungicides. Fortification
of foods with vitamins and other food accessories may create direct and
indirect odor problems of concern not only as possible contaminants of
the product but also as esthetic nuisances.
McCord and Witheridge (1949) discussed practical odor problems
in the food industry, in ventilation, and in the water supply. Cartwright
and Kelley (1954) gave pertinent examples of the problems of identifying
foreign odors in foods. The food scientist's problem in this area is an
industrial one, including deodorization, evaluation of quality, preferences,
acceptance, and rejection (see Dove, 1947). The production of masking
agents is now an important business. The use of chlorophyll is an ex-
ample of the importance the public attaches to the field, even if the odor
modifier in this case may not be effective. Harrison et ah (1953) main-
tained that a piece of flavored gum containing 4 mg of soluble sodium
or potassium copper chlorophyllin effectively reduced breath odor fol-
lowing ingestion of onions or beer or after cigarette smoking. Other tests
have not been so positive. Odors can also serve as danger signals, i.e.,
the odors of spoiled meat, rancid fat, and moldy foods.
Although little is known of the exact nature of the causal agent of
many natural odors, through olfaction we can recognize odors that still
elude chemical identification. By smelling we can identify compounds
in mixtures. Furthermore, we expect some things to smell: leather,
tobacco, fish, flowers, hospitals, garages, drug stores, shoestores, cream-
eries, gymnasiums, bakeries, dairies, wineries, and breweries.
B. FLAVOR
The flavors of food products (probably largely odors) are also much
stressed in the food industry. As Brozek (1957) noted "Flavor is a
complex sensation, with taste, aroma and feeling as the three categories
of components." This is recognized in the flavor profile procedure
(Chapter 8, Section V), where five characteristics of flavor are measured:
over-all impression ("amplitude") of aroma and flavor, perceptible aroma
and flavor factors, intensity of each factor, the order in which the
factors are perceived, and aftertaste (see Caul, 1956).
The growth of the spice industry is one indication of how important
flavor has become in our diet. Advertising readily emphasizes flavor
properties—real or imagined. Consider "purity, body, flavor" (Ballantine
Ale), "brisk flavor" (Lipton's tea), "fascinating artificial flavor" (Wrig-
ley's Juicy Fruit gum), "famous for its flavor" (Pride of the Farm catsup),
etc. The effect on flavor of added salt, sugar, acid, spices, monosodium
glutamate, meat tenderizer, etc., is receiving much current interest. The
4 1. SENSORY EVALUATION PROBLEMS OF THE FOOD INDUSTRY
use of gas-liquid partition chromatography has greatly increased our
knowledge of the distribution of volatile materials in various foods, but
few studies on identification of volatile compounds have indicated their
relationship to the sensory properties of flavor (see Chapter 11, Sec-
tion II).
The food scientist must advise the producer on how production
practices affect the composition and quality of the raw material and the
processed end product. He must advise the breeder on the desirable
color, odor, taste, and textural components of the new plant or animal,
and the relation of these to processed quality and consumer accepta-
bility and preference. Finally, within the food processing plant there are
innumerable problems relating to processing variables, new-product de-
velopment, quality control, and consumer acceptability and preference.
Even when the product enters the channels of trade, the food scientist
must be conscious of the potential changes in the sensory quality of
the food.
III. The Senses
Since the senses, particularly taste and smell, are intimately associated
with food appreciation, and hence with consumption, the study of their
physiology and reaction to stimuli is fundamental to food science.
A. SENSORY RECEPTORS
The sensory receptors are the detectors which inform us of physical
and chemical changes in our environment. These specialized cells are
usually sensitive to a single stimulus, but under certain circumstances
may react to other stimuli. The classification of sense organs in terms of
the sensations they mediate is a tenuous one since there is no basis for
the opinion that the nature of the sensation is determined by the re-
ceptor organ. Actually the sense organs convey, not the true properties
of the world, but only a spatial or chronological picture.
The sense organs of animals consist of sensory cells or groups of
cells which respond to stimuli and transmit an impulse via the nerves to
the brain. The essential property of the sense organ is irritability—to
either chemical or physical changes in the environment or within the
organism. The receptor may be a neuro-sensory cell or it may be a
secondary sensory cell which transmits a stimulus to the nerve and
thence to higher brain centers. Definite areas in the brain are stimulated
by the sensory input from the receptors. In higher animals the sense
organs, in addition to receptor cells, have various mechanisms for pro-
tecting, supporting, or conveying stimuli to the receptor cells. Thus there
is a great diversity of receptor cells and of sensory nerve terminations,
III. The Senses 5
which accounts for the large number of special senses. The response of
the sensory cells increases as the stimulus increases—up to a point. The
response of the nerve depends on the frequency of the electrical dis-
charge of the nerve; the higher the frequency the stronger the sensation.
Sensory receptors also vary in sensitivity.
Even quite primitive animals have highly specialized neuro-muscular
systems. Prosser (1954) summarized recent investigations on new types
of receptors. Receptors sensitive to carbon dioxide or to oxygen are found
in many animals. The tongue of the frog has specific water receptors.
Hygroreceptors have been found in the antennae of several insects.
Tribolium adults, for example, showed a preference for lower humidity
in the range 30 to 100% relative humidity, distinguishing differences of
5%. Water receptors have also been postulated for man, based on certain
contrast taste reactions. This research is now being pursued very actively
in Sweden (Zotterman, 1957, 1961; Zotterman and Diamant, 1959).
Based on Aristotle's authority, man is said to possess five primary, or
major, senses: sight, hearing, touch, smell, and taste. Of these, the last
two are the most primitive. For the lower animals these senses are of the
utmost importance. Fish, for example, have chemoreceptors over much
of their exterior surface. In the higher animals these specialized chemo-
receptors are so localized as to sample the intake of food. In man,
location of the taste receptors in the mouth, and the olfactory receptors
in the nose, makes it possible to taste and smell ingested foods simul-
taneously. Other senses now generally recognized include muscular and
visceral, heat, cold, pain, hunger, thirst, fatigue, sex, and equilibrium.
As many as 22 special senses or subdivisions of these have been recog-
nized by psychologists.
Many animals cannot hear, and some have no perception of light,
but all forms of animal life react to chemical stimuli. In man, at least
three different senses respond to certain chemical stimuli: taste, smell,
and the so-called common chemical or pain sense (Chapter 4, Section
III,E). The chemical senses aid animals in their search for and recogni-
tion of food, serve as danger signs, and in some cases function in propa-
gation. Man is primarily sight-guided in his search for food, but pigs,
dogs, and other animals are scent-guided.
There are many known facts about the senses, but few unifying
theories. Experimentation in this field is difficult, and the gaps in our
knowledge are large. Some say that the senses of smell and taste are too
simple for elaborate description. Vision and hearing, with their analytical
receptor systems, may appear to be more complex, though Mclndoo
(1927) and Boring (1942) do not think so. Smell, at least, has a great
complexity of qualities, and the olfactory membrane, even though its