Sensory evaluation of
fruits and vegetables
1
2




Quality is an elusive property which can be
defined as the sum total of those attributes which
combine to make fruits and vegetables
acceptable, desirable, and nutritionally valuable
as human food.
The quality components are presented in Table 1.
It is essentially a composite concept which can
be broken down into a number of distinct yet
related aspects.
In the first place, appearance is obviously of
significance and can be appreciated by visual
examination.
3
4
Defects, due to several causes, which
detract from the acceptability of a product,
can be easily identified.
 The size and shape of individual units is a
factor in quality, while the development of
other attributes indicates the stage of
maturity.
 An especially important visual feature is
the color of the external surface.

5
II. SENSORY EVALUATION



Appearance, although most important, is by no
means the sole criterion of quality.
Important also are the properties appreciated
through other human senses: those of taste, smell
and touch, which can be grouped together under
the heading of color, flavor, and texture.
The attainment of a satisfactory color, flavor, and
texture may often be associated with a certain
development of color, but appearance can be a
deceptive and completely satisfactory way of
assessing flavor and texture.
6
7
8
9
10


Differences in growing conditions, in harvesting
procedures, and in postharvest treatments
combine with the variability of the produce itself
to wide variations in quality, and many countries
have minimum standards and systems of grading
in an attempt to maintain some sort of
consistency in the general quality of produce
reaching the consumer.
The market for fruits and vegetables is an
international one and the present trend is towards
greater international standardization of grades of
quality of fruits and vegetables.
11
FAO (Food and Agricultural Organization) and 
WHO (World Health Organization) have
developed a Codex Alimentarius which has
standards for a complete range of foods.
The Economic Commission for Europe (ECE) 
pioneered the formulation of international
standards for fresh fruit and vegetable
commodities and a number of existing European
standards have already been adopted by the
Organization for Economic Cooperation and
Development (OECD), a body which includes
the countries of western Europe, U.S., and
Canada.
12
There is every reason to believe that in due
course the standards laid down by the
OECD will receive world-wide
recognition and that a complete uniformity
of standards will finally be achieved.
 The OECD scheme lays down certain
minimum requirements for material
entering the international market and also
institutes a number of quality classes

13

The minimum general requirements are as
follows:
I. The fruits or vegetables should be
healthy and sound, that is to say, free from
blemishes liable to affect their natural
powers of resistance, such as traces of
deterioration or decomposition, bruises, or
unhealed cracks.
14

2. They should be whole, clean, practically
free from extraneous matter, free from any
foreign taste or smell and without
abnormal surface moisture.
3. They should be of normal size and
appearance in regards to the variety,
season and production area.
4. They should have reached a degree of
maturity which will ensure the arrival of
the produce in good condition.’
15




Three distinct classes are designated for quality:
(1) an “Extra” Class to include “produce of superior
quality, of the shape, appearance, color and taste
characteristic of the variety, virtually free from
blemishes affecting their external appearance and
particularly carefully packed”;
(2) Class I, “produce of good quality, ‘commercially’
free from blemishes and carefully packed”; and
(3) Class El, “produce which may have certain
blemishes not impairing its intrinsic quality and
which compiles with the minimum general
requirements defined above”.
16
Specific standards are already laid
down for a number of individual
commodities.
 In these, the necessary requirements
for inclusion in each quality class are
described in considerable detail, with
explanatory illustrations, so as to
enable these standards to be applied
as uniformly as possible throughout
the various member countries

17

The above methods and other systems
of grading used in connection with
trade between countries that are not
members of the OECD are applied to
specific fruits and vegetables crossing
international boundaries, but
government departments and trade
associations in many countries also
operate their own internal systems of
quality grading.
18


Minimum standards are generally required
by law, but grade specifications are often
voluntary, for example, as those drawn up
by the Agricultural Marketing Service of the
United States Department of Agriculture, in
cooperation with various groups interested
in the marketing of fresh and processed
fruits and vegetables.
In the United States, and to a lesser extent
in other industrialized countries, a
substantial part of the fruit and vegetable
crop is taken by the processors and
requirements are not necessarily the same
as those which apply to the producer.
19
The quality of specifications for grading of
fruits and vegetables is not easy, since
several of the attributes which go to make
up quality are essentially subjective
properties.
 Quality specifications inevitably lack
precision and even when written up in
considerable detail, they still suffer from
the absence of satisfactory objective
methods of measurement.

20




The United States assesses the quality of fresh fruits and
vegetables by scoring a sample marked for different
quality attributes by reference to a special scoresheet.
In this way, by adding the marks accorded for different
features, a total score is obtained and this can be used as
a measure for overall quality and a basis for quality
grading.
The use of such a system raises the problem of deciding
what proportion of the total available marks would be
allocated to each of the various properties contributing
towards the general quality over all the produce.
The U.S.A. uses a maximum score of 100
21
III. ORGANOLEPTIC QUALITY
EVALUATION

Uniform samples are prepared (Figure 1) for quality
evaluation. Organoleptic appraisals are made for color,
flavor, texture, and aroma by a panel of ten trained
judges or by a large consumer panel of nonsmokers.
Numerical values (I0—Jike extremely—to I—dislike
extremely) are assigned to fresh and processed fruits and
vegetables (Table 2). The judges are instructed to
appraise each sample and encircle the phrase which best
describes their feelings about the sample. Following
judging, preference scores for each sample are added
together and divided by the number of judges to find the
final average score. The samples are always
22
23

put in coded cups, placed on trays and
placed in a judging room. The judging
room is furnished with individual
cubicles, each equipped with daylight
intensity for color as nearly as possible
(Figure 2). Each member of the panel
judges the flavor, color, texture and
aroma (Figure 3).
24



The flavor is tested for tasting sweetness,
saltiness, sourness, and bitterness by the
location and distribution of taste buds over
the tongue and their specific locations
(Figure 4).
Texture is judged by mouth feel or
chewiness. Aroma is evaluated by smelling
the samples.
Color is judged by its original and natural
color and gloss40
25
IV. OBJECTIVE QUALITY


Color, flavor, and texture are complex
properties. In order for the best possible use
to be made of available methods for
measurement in these cases, it is important
that a proper
understanding be obtained of the particular
attribute and of the mechanisms whereby it
is appreciated by the individual consumer.
26
27



A. COLOR
The appreciation of the appearance of any
object depends on the formation of an
image on the retina of the eye.
In order that an image be formed, a certain
minimum amount of light must reach the eye
from the object.
The glossiness of the surface of an object
depends on the manner in which light is
reflected from that surface, which in turn
depends on the smoothness and regularity
of the surface.
28
29



Flavor
Flavor is a property which is largely due to
the stimulation of the chemical senses of :he
consumer, both of taste and smell.
Minor contributions to the overall sensation
of flavor nay also be made by receptors
concerned with temperature and touch, but
taste and smell re the dominant aspects of
this most subjective of all quality attributes.
30



Texture
The term texture, as applied to a fruit or a
vegetable, has been interpreted very
broadly to include certain features of
appearance and of “hand feel” in addition to
the textural characteristics experienced
during the actual eating of the fruit or
vegetable.
In the present context, the word texture will
be used to cover only those properties
which are perceived by the sense of touch
in the mouth.
31
32
V. NONDESTRUCTIVE QUALITY
EVALUATION


Fruits, vegetables, and their products are
more complex, primarily due to the fact that
they are available in several forms, from
freshly harvested produce to processed
products of several types.
It is difficult to use the same method or
principle for quality control through all these
stages, and often times several methods
need to be employed for quality control of
different by-products of the same
33
34
A. MATURITY AND RIPENESS
EVALUATION
The ripentng or maturity of fruits and/or
vegetables is associated with changes
in color, flavor, and texture that lead to
the state at which the fruit or a
vegetable is acceptable to eat.
 The readily apparent phenomena
associated with the ripening and
maturity of most fruits and vegetables
include changes in color,

35
36
B. DEVELOPMENT OF AUTOMATIC
SORTING MACHINES



Most of the fruits and vegetables do not
mature at the same time because of the
biological and environmental variability.
The handpicking and sorting of only mature
fruits necessitates a large labor force.
This represents a major expenditure in time
and money to the fruit or vegetable grower.
37
38
C. DETECTION OF EXTERNAL AND
INTERNAL DEFECTS

Fruits and vegetables can easily be
sorted into different grades based on
the differences in reflectance
properties induced by external and
internal defects including mechanical
injuries that occur during harvesting
and postharvest handling as well as
certain microbial diseases.
39
40
41
42