BASED ON THE SENSORY EVALUATION OF FRUITS AND VEGETABLES .

1. TEXTURAL ATTRIBUTES OF FRUITS
AND VEGETABLES
BY : HITESHINI.T.Y
ROLL NO: 20FST30
COLLEGE : ST JOSEPH’S COLLEGE (AUTONOMOUS)

2. CONTENT
• INTRODUCTION
• PHYSICAL CHARACTERISTICS OF FOOD
• TEXTURAL ANALYSIS OF FOOD
• REFERENCE

3. INTRODUCTION
 According to Bourne (1982) the textural properties of a food are the “group of physical characteristics that
arise from the structural elements of the food, are sensed by the feeling of touch, are related to the
deformation, disintegration and flow of the food under a force, and are measured objectively by functions
of mass,time,and distance.”
• Texture of food products is defined as all the rheological, mechanical and structural attributes of the product
perceptible by means of mechanical, tactile, visual as well as auditory receptors.
OBJECTIVE: It is important to identify the main elements of tissue strength and to determine which mechanical
properties are responsible for the textural attributes of interest.
Psychometrics, that as the study of the measurement of human response, is a fairly young science and has not
been extensively applied to fresh fruits and vegetables, so the contributions of mechanical properties to
sensory texture are not well understood .
 Texture is the sensory and functional manifestation of the structural, mechanical and surface properties
of foods detected through the senses of vision, hearing, touch and kinesthetics.
 Texture is a sensory property which can only be perceived and described by humans (and animals) and
any instrumental measurements must be related to sensory responses.
 The texture of an object is perceived by the senses of sight (visual texture), touch (tactile texture), and sound
(auditory texture)

4. Fruits and vegetables (tissues) are viscoelastic, implying that they exhibit combined
properties of ideal liquids, which demonstrate only viscosity(flow), and ideal solids,
which exhibit only elasticity (deformation).
Viscoelastic behavior means that force, distance, and time, in the form of rate,
extent, and duration of load, determine the value of measurements.
• Texture OF FRUITS : firmness, grit character,mealiness.
• Texture OF VEGETABLES :mealiness, succulence, fiber,maturity.

5. Consumer acceptance
• People sense texture in numerous ways: the look of the product, the feel in the
hand, the way it feels as they cut it, the sounds as they bite and chew, and, most
important of all, the feel in their mouth as they eat it. It is generally accepted that
texture relates primarily to mechanical properties of the tissue.
• Instrumental tests may be imitative, that is they imitate human testing methods,
or they may measure fundamental mechanical properties or they may indirectly
estimate texture by measuring some related optical or chemical property.
• Only people can judge quality, but instruments that measure quality-related
attributes are vital for research and for inspection.

6.  Consumers have clear expectations for the texture of fresh cut vegetables and
fruits.
 Salad vegetables like lettuce, carrot, radish should be crisp. Soft fruits such as kiwi
and peach should yield to chewing without being mushy and apples should be
crisp and crunchy.
 While consumers generally cite flavor as the most important quality attribute for
fruits and vegetables, textural defects and the interaction of flavor and texture are
more likely to cause rejection of a fresh product .
 Undesirable textural attributes are the opposite of the desirable ones. Wilted
lettuce, limp carrots or celery, and flaccid radish are unacceptable as are crunchy
or mushy cantaloupes and peaches. Soggy or mealy apples are also likely to be
rejected.

7. PHYSICAL CHARACTERISTICS OF FOOD
The physical or the mechanical textural characteristics of foods are related to the
reaction of the food to stress and can be divided into primary parameters of
hardness, cohesiveness, viscosity, adhesiveness, and into secondary (derived)
parameters of brittleness,chewiness and gumminess.
 HARDNESS: Force required to compress a substance between the molar
teeth(solid foods) or between the tongue and palate ( semi solid) to a given
deformation or penetration and designated as soft, firm or hard.
 COHESIVENESS: It is the extent to which a material can be deformed before it
ruptures and is dependent upon the strength of internal bonds.
 (directly dependent on tensile and compression strength of food)

8.  TENDERNESS, CHEWINESS OR TOUGHNES : These characteristics are defined as the
energy required to masticate a solid food product to a state ready for swallowing and
involves compressing, shearing etc.
 BRITTLENESS, CRUNCHINESS AND CRUMBLINESS: These three characteristics are due to
the high degree of hardness and low degree of cohesiveness.
 ELASTICITY: It is the rate at which the deformed material regains its original condition
after the removal of the deforming force.
 ADHESIVENESS: It is the force necessary to remove the material that adheres to the
mouth during eating and is described as sticky, tacky or gooey.
 VISCOSITY: It is the force required to draw a liquid from a spoon over the tongue and
described as thin, watery or thick.
 GUMMINESS: It is the energy required to disintegrate a semi-solid food. It is characteristic
of products with a low degree of hardness and a high degree of cohesiveness.

9. TEXTURAL
ANALYSIS OF FRUITS AND VEGETABLES
SENSORYANALYSIS INSTRUMENT ANALYSIS
 Hand feel Succulometer
 Mouth feel Tenderometer
Pressure tester
Texture meter
Puncture meter
Fibrometer

10. SENSORY ANALYSIS
• Sensory evaluation of food texture by touch includes the use of fingers, lips, tongue, palate and
teeth.
HAND FEEL
• Mechanical characteristics – force to compress, resilience, stiffness
• Geometric characteristics – fuzzy, gritty
• Moisture content – oily, wet
• Thermal characteristics – warmth
• Non-tactile property - sound
• It is finger feel such as firmness in apples, softness in mango and plum and juiciness of citrus fruits, etc.

11. MOUTH FEEL
Szczesniak in 1966 grouped mouth feel characteristics as follows;
• Viscosity-related - thin, thick
• Feel of soft tissue surfaces related - smooth, pulpy
• Carbonation related - tingly, foamy, bubbly
• Body related - watery, heavy, light
• Chemical related - astringent, numbing, cooling
• Coating of the oral cavity related - clinging, fatty, oily
• Related to resistance to tongue movement - slimy, sticky, pasty, syrupy
• Mouth after feel related - clean, lingering
• Physiological after feel related - filling, refreshing, thirst quenching
• Temperature related - hot, cold
• Wetness related - wet, dry
Later in 1993, Bertino and Lawless grouped it into 3;
• Astringency
• Numbing
• Pain
It includes sensory characters such as chewiness, fibrousness, grittiness, mealiness and stickiness.

12. INSTRUMENTS
SUCCULOMETER
• It measures moisture content of fresh and processed.
• It uses compression to squeeze juice out of food as a measure of succulence.
• Succulometer, measures maturity in sweet corn; the amount of juice forced out of a
sample of corn under 500 pounds of pressure indicates maturity.
• It helps in obtaining the juice of the fruit.

13. TENDEROMETER
• It measures the tenderness and determines the maturity of the food sample taken.
• Compression and shear pressure is applied to determine the tenderness.
• The tenderometer was introduced in 1937 for measuring quality in peas.
• Tenderometer measures crushing and shearing.

14. PRESSURE TESTER
• It was introduced in 1925.
• It is light and portable instrument.
• It measures the maturity of various fruits.
• It consists of a cylindrical metal barrel, about 12 inches long and 1 inch in diameter, within which a
plunger works against a steel spring. The end of the plunger has interchangeable screw-on tips.
• The tip is placed against a pared spot on the fruit, and the barrel is pressed until the tip penetrates the
flesh.
• Firmness is expressed as the number of pounds of pressure required to penetrate the fruit and is read
from a scale on the barrel.

15. TEXTURE METER
It helps determine adhesiveness, chewiness, cohesiveness,
consistency, crispiness, crunchiness, elasticity,
extensibility, firmness, fracturability, gel strength,
gumminess, hardness, rupture strength, springiness,
stiffness, stringiness, texture profile analysis (TPA)
toughness, work to cut, work to penetrate and work to
shear of the raw material.

16. PUNCTURE METER
• It measures the amount of force required to penetrate a
sample to a specific depth.
• It also measures the maximum force required and the breaking
strength is obtained for a particular raw material.

17. FIBROMETER
• Fibrometer was introduced in 1948 to measure quality in
asparagus by measuring the resistance of asparagus stalks to
cutting.
• Fibrometer measures the cutting force required.

18. TEXTURAL PROFILE ANALYZER
• It is a double compression test for determining the textural
properties of foods.
• It is primarily concerned with the evaluation of mechanical
characteristics where a material is subjected to a controlled
force from which a deformation curve of response is
generated.

19. Instrumental or objective methods of texture evaluation
can be grouped into three classes
Fundamental
tests
Empirical tests

20. Instrumental or objective methods of texture evaluation
can be grouped into three classes—
• Fundamental tests: measure properties that are inherent to the
material and do not depend on geometry of apparatus. e.g. strength,
Poisson’s ratio, and various moduli such as Young’s modulus, Shear
modulus, and Bulk modulus. Further classified into:
1.Quasi-static test 2.Dynamic test
• Empirical tests :cover a wide range of simple and rapid tests, including
puncture, compression, extrusion, shear, and others, which measure one
or more textural properties and are commonly used in quality control
applications. Most methods used for the evaluation of the textural
properties of fruits and vegetables are empirical or semi-empirical.
•

21. CLASSIFICATION OF TEXTURE TEST
DESTRUCTIVE TEXTURE
TEST
NON –DESTRUCTIVE
TEXTURE TEST

22. Destructive Texture Tests for Fruits and Vegetables
• Puncture test(testers) based on the Magness-Taylor pressure tester called as the Magness-Taylor fruit
firmness tester, are used to measure firmness of fruits and vegetables to estimate harvest maturity or for post-harvest
inspection.
• An 11.11nm( 7/ 16 inch ) diameter probe with a radius of curvature of 8.73mm is used for apples.
• A 7.94-nm1(5/16 inch) diameter probe with a radius of curvature of 5.16 mm is used for cucumbers, kiwifruits,
mangoes, papayas, peaches, pears, plums, avocados .
• A thin slice of skin (about 2 mm thick and slightly larger diameter than the probe) should be removed from the area to
be tested . It is recommended that steady force should be applied to insert the probe to the inscribed depth mark in 2s .

23. Compression Test
Whole fruit compression involves pressing an intact fruit or vegetable between parallel flat plates or
between a pair of probes until a specified force or deformation is achieved or until rupture occurs . Modulus
of elasticity , modulus of deformibility and stress index for fruits can be calculated from such measurements,
although often only maximum force or distance is reported. Whole fruit compression is affected by fruit
morphology, size, and shape, as well as by cellular structure, strength, and turgor. Rupture force of intact
watermelons , whole tomato compression, and apple tissue compression are examples of compression
measurements.

24. Kramer Shear or Compression-shear Test
The Kramer shear cell actually applies compression, shear, and extrusion to
the sample .
The functional part of the test equipment is a sample cell with multiple dull
blades that pass entirely through the sample volume . The original
Kramer cell is approximately 67 x 67x 63mm with ten 2.9-mm thick
blades; several adaptations with differing volumes and differing blade
numbers and sizes have been used . The cells can be mounted in any
universal testing instrument of suitable force capacity. Usually only the
maximum force to pass the blades entirely through the sample is
reported, although the entire force/deformation curve can be obtained.
Forces are dependent on quantity and Organization of the sample within
the sample cell. A sample size of 100 g is recommended for the standard
cell size. Because of the combination of destructive forces applied to the
food, it sometimes relates fairly well to sensory assessments of texture .

25. Tension Tests
• Tensile tests measure the force required to pull a sample
apart . Failure can be through cell rupture , cell separation,
or a combination of both . Tensile measurement has not
been widely applied to fruits and vegetables because it is
not related to chewing and because of difficulties in
making the measurements, it requires gripping the ends of
the sample, gluing moist tissues to probes, or shaping the
sample for gripping with claw-like holders without
damaging the tender tissues. Researchers often examine
the broken ends where they have been pulled apart to
determine the mode of fracture .Microscopic analyses of
the broken ends reveal that , cells from ripened fruits which
tend to be crisp(apple and watermelon) usually break or
rupture, and cells from ripened soft fruits (banana,nectarine
and kiwifruit) tend to separate at the middle lamellae .

26. Non-destructive testes for fruits and vegetables
useful for research on post-harvest physiology because fruit can be measured at the beginning of experiments
to determine the maturity or condition and because the same fruit or vegetable can be measured repeatedly,
minimizing or eliminating the variation among individuals.
Laser-air Puff
A non-destructive, non-contact firmness detector was recently
patented that uses a laser to measure the deflection caused by
a short puff of high-pressure air, similar to some devices used
by ophthalmologists to detect glaucoma. This is essentially a
compression tester. Under fixed air pressure, firmer products
deflect less than softer ones. Laser-puff readings correlated
fairly well with destructive Magness-Taylor firmness values for
apple, cantaloupe, kiwifruit , nectarine, orange , pear, peach ,
plum, and strawberry .

27. Sonic or Acoustic Tests
Sonic (or acoustic) vibrations provide a means of measure fruit and
vegetable firmness.
The traditional watermelon ripeness test is based
on the acoustic principle, where one thumps the melon and listens
to the pitch of the response.
When an object is caused to vibrate, amplitude varies with the
frequency of the vibration and will be at a maximum at specific
frequencies determined by a combination of
the shape, size , and density of the object and, in the case of fruits
and vegetables, by their turgor pressure . The points of maximum
amplitudes are referred to as resonances. For objects of similar size
and shape , the firmer the material the higher the resonance
frequencies . Thus, resonant frequencies decrease as fruit ripens .
Resonance measurement can be achieved by applying an impulse or
thump that contains a range of frequencies.

28. Reference
 Harry T. Lawless, Hildegarde Heymann; 2010; Sensory Evaluation of
Food
 Pal J. Molnar, Vol II, Fruits and Vegetables, food quality and standards
 P.W. Board, 1988, Quality control in fruit and vegetable processing, food
and agriculture organization of the United Nations
 Measuring and keeping quality, 1960, Year book of agriculture
 Judith A. Abbott“, TEXTURAL QUALITY ASSESSMENT FOR FRESH FRUITS
AND VEGETABLES, Quality ofFresh and Processed Foods. edited by
Shahidi et al.Kluwer Academic/Plenum Publishers, 2004 .
 Diane M. Barretta; John C. Beaulieub; Rob Shewfeltc, Color, Flavor,
Texture, and Nutritional Quality of Fresh-Cut Fruits and Vegetables:
Desirable Levels, Instrumental and Sensory Measurement, and the
Effects of Processing, 05 April 2010.

29. THANK YOU