Principles & practice of objective texture measurement. Different type of Tests for Measuring Food Texture and machines used for measuring these test.

1. Principles & Practice of
Objective
Texture Measurement
Submitted by:
Ruchika Zalpouri
Kulwinder Kaur
Pratik
Baldev Singh

2. Why do we need texture classification system?
Wide range foods exhibit various types of textural and
rheological properties, to evaluate these properties a
wide variety of methods are used.
Because:

3. • Liquids, gels, fibrous foods, agglomerates of turgid cells,
unctuous foods, friable, structures, glassy foods,
agglomerates of gas-filled vesicles, and combinations of
these
Matz
(1962)
• Liquid foods, gel-like foods, fibriform foods, cellular-form
foods, edible oils and fats, and powdered foods.
Sone
(1972)
Classification of foods on the basis of their textural
properties

4. Types of Tests for Measuring Food Texture

5. • Performed by instruments
• Measure real textural properties • Measure physical properties
that correlate with textural
properties
Types of Tests for Measuring Food Texture

6. Direct
Fundamental Empirical Imitative

7. Fundamental Tests
• These tests measure well-defined rheological properties
• Fundamental tests generally assume
(1) Small strains (1–3% maximum)
(2) The material is continuous, isotropic and homogeneous and
(3) The test piece is of uniform and regular shape.
• Generally slow to perform.

8. • Do not correlate as well with sensory evaluation as do empirical tests.
• Not used to any great extent in the food industry but in research
laboratories.
• Use expensive equipment.
• E.g.: Stiffness coefficient, which is essentially an index of Young’s
modulus of elasticity.

9. Empirical Tests
• Measure parameters that are poorly defined.
• Most widely used in the food industry.
• The tests are usually easy to perform and rapid.
• Use non-sophisticated inexpensive equipment.

10. PROBLEMS
• Poor definition of what is being
measured
• The arbitrariness of the test
• No absolute standard is available
• Applicable for limited number of
commodities

11. Imitative Tests
• Imitate the conditions to which the food material is subjected in practice.
• This class may be considered as a subtype of empirical test because the
tests are not fundamental tests.
• E.g. Farinograph and Dough-testing apparatus that imitate the handling
and working of bread dough, the Bostwick consistometer etc.

12. Comparison of different systems of objective texture measurement

13. Fig: Schematic representation
of the ideal texture measuring
apparatus and its derivation
from empirical, fundamental,
and imitative instruments.
(From Bourne, 1975b)

14. Advantages
Ideal texture measuring apparatus

15. 15
TypesofObjective
MeasuringInstruments
Force measuring
Distance measuring
Time measuring
Work, energy and power
measuring

16. Objective Methods for Measuring Food Texture

17. Objective Methods for Measuring Food Texture

18. ForceMeasuring
Instruments
18
Puncture
Compression – extrusion
Compression
Cutting - shear
Tensile
Torsion
Bending and snapping

19. Puncture Test
• The puncture test measures the force required to push a punch or probe
into a food.
• The test is characterized by
(a) A force measuring instrument,
(b) Penetration of the probe into the food causing irreversible crushing or
flowing of the food, and
(c) The depth of penetration is usually held constant
• Puncture test instruments are maximum-force instruments

20. Application Ripeness and bioyield point of fresh fruits and
vegetables,
Ripeness/hardness of cheese,
hardness of confectionery and
Spreadability of butter and margarine
Parameters Firmness, Hardness
Probes used Cylinder Probe (generally from 2mm – 8mm in
diameter), Magness-Taylor Puncture Probe, or Ball
Probe and needle probe

21. Puncture testing instruments
Number of probes
Constant rate of application of force
Constant rate of travel of probe

22. On the basis of
number of
probes
Single-probe
Multiple-
probe
Chatillon Bloom Gelometer
Armour Tenderometer
Christel Texture Meter

23. • Armour Tenderometer
• Bloom Gelometer
Constant rate of
application of force
• Instron
• Texture Analyzer
Constant rate of
travel of the probe

25. Theory of the Puncture Test:
Bio yield point
Fig: Schematic representation
of the five different types of
force–distance curves that
are obtained in puncture
tests.

26. • Boussinesq equation: According to this equation the stress in the food is
highest at the perimeter of the punch and lowest at the center of the
punch. (Morrow and Mohsenin (1966))
Where,
P - pressure at any point under the punch,
F - total force applied to punch,
a - radius of punch, and
r - distance from center of punch to stressed area.
Note: This equation only applies before the yield point is reached; that is, during the
deformation stage. The Boussinesq equation does not apply during or after the yield
point.

27. • Bourne (1966b) has shown that the yield-point force is proportional to
both the area and perimeter of the punch, and to two different textural
properties of the food being tested.
Fig: Schematic representation of a puncture test.
Where,
F - force on the punch (N, kg or lb);
Kc- compression coefficient of
commodity (N mm-2);
Ks- shear coefficient of commodity
(N mm-1);
A- area of the punch (mm2);
P- perimeter of the punch (mm);
C- a constant (N).

28. Semi-infinite Geometry
• Diameter of the punch less than one-third the diameter of
the sample

29. Size and shape of the punch
Nature of the food
Depth of penetration
Number of punches
Speed of travel of the punch

30. Advantages of the Puncture Test

31. Baldev Singh will present further

32. Bloom Gelometer
• Named after: Oscar bloom
who patent the process.
• Measure : Strength of gelatins
and gelatin jellies
• Consists: hopper, plunger

33. gelatin
1/2-inch-
diameter
punch gelatin
desserts
1-inch
diameter
punch
 A lever is tripped allowing lead shot to flow from
the hopper into a lightweight aluminum dish on
the scale supported by the punch pan at the rate
of 200 ± 5 g per 5 s.
an electrical
contact shuts
offthe flow of
shot
Penetration
of 4mm The shot is
weighed and
the weight of
shot in grams
Bloom of
gel

35. Stevens LFRA Texture Analyzer
• Developed : Leatherhead Food
Research Association (LFRA) in
England
• Designed : Perform the standard
Bloom test + other tests
• The instrument stands about 50
cm high, 24 cm wide, and 23 cm
deep, and weighs about 12 kg.

36. Stevens LFRA Texture Analyzer
• The standard probe is a 1/2-in.-
diam flat-faced straight-sided
acrylic punch
• Four speeds of punch travel are
available: 12, 30, 60, and 120 mm
min-1.
• The maximum stroke of the punch
is 15 cm.
• This instrument is a useful general-
purpose puncture tester for soft
products.
• It is used on meat pastes, foams,
various gels, and some fats.

37. Maturometer
• Developed in Australia.
• Extensively used to measure the
maturity of fresh green peas
• It consists of 143 1/8-in.-diam
flat-face punches set in an array
of 11 rows by 13 rows with
individual punches spaced on
7/16-in. centers.
• A metal plate containing 143
matching countersunk holes is
positioned underneath the
punches.

38. Maturometer
• Australian conditions that peas harvested at a
maturometer reading of 250 lb gave the maximum
yield of highest quality peas for canning.
• lower figure is needed for the maximum yield of best-
quality peas for freezing.
• Maturometer Index (MI) as a basis of payment for
quality
• Grade 1 (canning) consists of peas in the range of 230–270
MI.
• Grade 2 (canning) consists of peas in the range of 190–230
and 270–320 MI.
• Grade 1 (freezing) consists of all peas up to 200 MI

39. Christel Texture Meter
• Christel (1938) introduced and patented an
instrument (Christel, 1940) for testing peas that is
nominally a puncturing device
• Peas are placed in a covered container and 28
punches (25 in later models), 4.8 mm in diameter,
were forced through the peas, passing through
matching holes in the lid and bottom of the container
• The punches passed up through the bottom of the
container and emerged from the top.
• The force is registered on an hydraulic pressure gauge
with a force capacity of 100 or 300 lb

40. Armour Tenderometer
• This instrument consists of
an array of -in.-diam
stainless-steel probes, 3 in.
long, with the last inch
tapered to a point
 This instrument utilizes manual pushing to force
the ten-needIe probe into the meat
 The force required is sensed by the strain gauge
force transducer on which the probe is mounted.
 The bracket on the probe assembly is for indicating
when the depth of penetration is exactly two
inches.

41. Other Puncture Testers
Universal Testing Machines provide a number of
probes that are suitable for puncture tests
Compression–Extrusion Testers
• Force applied to sample until it flows through slots,
holes, or annular spaces
• Maximum force to extrude product is measure of
firmness or tenderness
• Firmness, spreadability, product consistency,
extrudability, sachet/tube removal force,
syringeability. work of extrusion, cohesion
• Viscous materials including some gels, fats, peas,
catsup

42. FMC Pea Tenderometer
• Developed by the Food Machinery
Corporation for measuring the
quality and maturity of fresh
green peas
• A motor-driven grid of 19
stainless-steel blades 1/8 in. thick
and spaced 1/8 in. apart are
rotated through a second reaction
grid of 18 similar blades.
• The peas placed in the cavity
between the two grids are cut and
extruded through the slits
between the blades.

43. FMC Pea Tenderometer
• The reaction grid is mounted in
bearings and is free to rotate, but
its rotation is resisted by a
weighted pendulum hanging from
the second grid which swings out
of the vertical as the reaction grid
rotates.
• The force exerted during
extrusion of the peas is reflected
in the angular movement of the
pendulum and is recorded by a
pointer that moves across a
sinusoidal scale.

44. FMC Pea Tenderometer
• widely used as an index of quality and price to be paid for the peas,
• the problem of calibration: If the blades become dented or warped, a
friction component is introduced

45. Texture Press
• Developed at the
University of Maryland
• commonly known as the
‘Kramer Shear Press,
• Now it is known as the
Food Technology
Corporation Texture Test
System, abbreviated to FTC
Texture Test System.

46. Texture Press
• ‘Texture Press,’ is 64 cm wide, 60
cm deep, 90 cm high, and weighs
about 95 kg
• Designed for hard reliable work
under wet food processing plant
conditions.
• Driven hydraulically: An electrically
driven oil pump powers the ram to
which the moving parts are
attached. Switches control the up
and down motion of the ram.
• The working space for the test cells
is 4 *4.5 in.

47. Texture Press
• Force is measured by means of a force transducer
placed between the bottom of the ram and the test
cell
• Six force transducers ranging from 50 to 3000 lb
capacity are available.
• A special force transducer is available for use with
fresh peas, which is calibrated directly in Pea
Tenderometer units, and covers the range of 0–500
equivalent Tenderometer units. (1 Tenderometer~
approximately 6.2 lb/force)
• The speed of travel of the hydraulic ram is infinitely
variable from 0 to 20 in. min1 by adjusting a flow
control valve located in the oil supply pipeline to the
ram

48. Texture Press
• Texture Press consists of a
metal box
• 1/8-in.-wide bars spaced 1/8
in. apart are fixed in the
bottom of the box
• A set of ten blades, each 1/8
in. thick and in. wide,
spaced 1/8 in. apart, is
attached to the press ram.
• A metal lid containing a set
of bars that match the bars
in the bottom fits over the
box

49. Ottawa Pea Tenderometer
• The Ottawa cell is designed to
produce shear stresses in a
specimen by forward extrusion
was adapted specifically for
measuring the maturity
• The standard test cell is
constructed of 1/2-in.-thick
aluminum plate and is square in
cross section. The internal cross-
sectional area of the cell is 30 cm2
(55 mm along the edge), and it
stands about 13 cm high.

50. Ottawa Pea Tenderometer
• A rectangular plunger made of 1/2-in.-thick aluminum plate is
attached to a 1-in.-diam shaft.
• The plunger has a clearance of 0.275 mm from the wall on each side
to eliminate friction.
• The peas are extruded through a replaceable wire grid that slips into
the bottom of this cell.
• The plunger is driven down into the test cell at 18.2 cm min1 by a
synchronous motor connected through a gear box to a single vertical
screw that moves the crosshead.

51. Vettori Manghi Tenderometro
• This Italian-built instrument is similar to the FTC Texture Press in that it
uses an array of metal blades that move down and through slots formed by
a set of stationary
• The instrument is constructed of stainless steel and is driven by a hand-
powered crank handle.
• The capacity of the test cell is 166 ml, which is approximately one third the
450-ml capacity of the FMC Pea Tenderometer.
• An hydraulic gauge measures maximum force in Tenderometer units on a
0–250 scale.
• It is used mostly for measuring the maturity of fresh peas. It can be easily
disassembled for cleaning.

52. FirmTech 2
• This small instrument, weighing only about 7 kg, is
designed to test small fruits such as blueberries,
cherries, grapes, plums, and tomatoes.
• A small platen gently compresses fruits one by one.
• Two modes of compression are available:
• (1) measures deformation distance under a standard force;
• (2) measures force to attain a given deformation.
• A third option is to perform a puncture test using a
probe smaller than the fruit.
• A turntable has a number of depressions around the
perimeter, the size and number of depressions is
matched to the size of the fruit.

53.  The instrument is controlled by a
desktop or laptop computer.
 A fruit is placed on each depression
and the instrument is started.
 The fruit under the platen is gently
compressed, then the turntable
automatically rotates to bring the
next fruit under the platen and after
it has been compressed, it moves on
to the next fruit, and this process
continues until all the fruits on the
turntable have been tested.
 The load cell capacity is 45 N.
Approximately 3 s is required to test
each fruit.

54. Compression–Extrusion Test
This test consists of applying force into a food until it flows through an outlet
that may be in the form of one or more holes that are in the test cell.
The maximum force required to accomplish extrusion is measured and used as
an index of textural quality.
This type of test is used on viscous liquids, gels, fats, and fresh and processed
fruits and vegetables.

55. Figure: Typical force–
distance curve for
compression extrusion test

56. According to Voisey et al (1972)
1. Force reduces rapidly with further compression. This indicates that
resistance to shearing is the dominant mechanism of this test.
2. Force decreases slowly, indicating some shearing resistance combined with
some extrusion and possibly adhesion of the sample to test cell.
3. Horizontal plateau indicates either shearing of successive layers of the
sample or a combination of shearing, extrusion, and adhesion occurring
simultaneously.
4. Force steadily increases as extrusion proceeds indicating further
compression of the sample in addition to various amounts of adhesion,
extrusion, and shearing.

57. Szczesniak et al. (1970)
He concluded from extensive study that different foods undergo
different types of disintegration in the Texture Press. They made the
following postulates:
(1) In compression, force is proportional to (sample weight)2.
(2) In shear, force is proportional to sample weight.
(3) In extrusion, force is independent of sample weight.

58. Back extrusion test
Food moves in the opposite direction to the
plunger
Forward extrusion test
Food moves in the same direction as the
plunger
Compression–ExtrusionTest

59. Pros and Cons of the Back Extrusion Test
Easy to perform, and rapid
The force for the onset of
extrusion is independent
of sample weight.
It is not affected by free
liquid
It requires a high level of
force which may be
beyond the capacity of
some of the universal
testing machines in which
the back extrusion cell is
mounted

60. Compression Test
Uniaxial Compression
• The sample is compressed in one
direction and is unrestrained in the other
two dimensions.
Bulk Compression
• The sample is compressed in three
dimensions, usually by means of
hydraulic pressure.

61. Uniaxial Compression
• The platen that compresses the food should be larger in diameter than
the food specimen for a true compression test.
• When the platen diameter is less than the diameter of the food it
becomes a puncture test.
Poisson’s ratio Volume
= 0.5 unchanged
< 0.5 decreases
• It causes a change in shape

62. Uniaxial
Compression
Class A
Class B
• Nondestructive.
• The compression force is kept small to
ensure there is no fracture, breaking, or
any other irreversible damage done to the
sample.
• Deformation test which imitates the
squeezing of food in the hand.
• Destructive.
• The compression force is increased to a
level that ensures the sample will break
causing irreversible damage to the
sample.
• Also known as “Imperfect lubricated
squeezing flow”.

63. Bulk Compression
• It causes a change in volume but usually no change in shape.
• Seldom used in testing foods >>>> difficulty of performing a test
when force applied by means of hydraulic pressure.
• Foods contain variable amounts of entrapped gas, gases are
highly compressible, the amount of entrapped gas profoundly
affects the bulk compressibility of the food.

64. Application Fruit and vegetables, puffed cereals, cakes and
biscuits, confectionery and pharmaceuticals
Parameters Compressibility, compactability, springiness, stress
relaxation, creep compliance, crush strength,
firmness, elastic recovery
Probes used Cylindrical probe or a flat plate/platen
Compression Test

65. Cutting – Shear Test
Sliding of the plane of a body relative in
a direction parallel to the plane of
contact under the influence of a force
tangential to the section on which it acts
Action that causes the product
to be divided into two pieces.
Fig: Comparison of
(a) true shear failure with
(b) cutting–shear failure.

66. Warner-Bratzler shear test
To measure toughness of a product
Probe head consist of a ‘V’ shaped plate
The 2 side plates provided hold the sample until the sample
is cut by the ‘V’ shaped plate with angle ranges from 30 to
70º.
The maximum force needed to cut the sample is recorded

67. Kramer shear test
The action of this test is just biting the foods
It involves a combination to several plates as probe
Interaction between probe and sample involves
several force action:
1. Compression
2. Extrusion
3. Shearing

68. Tensile Tests
• A tensile test pulls or stretches a sample and as a result
elongation and tensile strength properties are measured in terms
of force required to stretch and distance or time upto which sample
can be stretched. E.g films, dough, gels, spaghetti, confectionery
and adhesives
• Tensile tests are also used for measuring stickiness or
adhesiveness of foods. E.g in packaging industries.

69. Tensile
Tests Uniaxial tension: Specimen is gripped at either end and
stretched until it breaks.
Bi-axial tensile: Test where the sample is held like a circular
drum skin and stretched in all directions by forcing a ball probe
through the center.
e.g testing films and tortilla

71. • In a torsion test, a force is applied to rotate or twist
one part of the object around an axis with respect to the
other parts.
• If a force of F newton is applied to a body at R meter
distance from the axis of rotation
Torque, T = F×R ,Newton meter.
• The major application of this test is in the rotary
viscometers is to measure the viscous properties of
foods due to its dependency on temperature.
Torsion Tests

72. According to Hamann, 1983,
• In torsion test
Even for large strains;
True strain (Hencky strain) = engineering strain (Cauchy strain)
• In uniaxial compression;
Even for large degree of compression
True strain (Hencky strain)>>Engineering strain(Cauchy strain)

73. • Torsion is produced when a pair of force twist
an object.
• This test is suitable for highly deformable
foods such as elastic gels.
Farinograph Mixograph
Torsion tests instruments

74. -Produces a pure shear
stress.
-Maintains sample shape
and volume during the
test.
-Tension, compression
and shear are created in
equal magnitudes i.e. 45o.
-Shaping and preparation
of the sample are time
consuming.
-Not suitable for sticky
foods such as caramels
and very soft foods such
as some cheeses
Advantagesoftorsiontest
Disadvantagesoftorsiontest

75. Bending and Snapping Test
• Bending and snapping tests are usually applied to food is in the
shape of a bar or sheet.
• Length/ thickness ratio is an important factor.
Fig: Two ways to perform bending and snapping tests

76. • This type of test can measure the fracture and break strength of hard
and brittle products (or their flexibility) by bending the sample, usually
until a break occurs.
• Fracturability/brittleness/crispness
• Example: Bar shape or thin products
• Small Three Point Bend Rig (length 70mm and width 80 mm)
• Large Three Point Bend Rig (length 240mm and width 90 mm)
Large Three Point Bend Rig Small Three Point Bend Rig

77. CRISP FRACTURE SUPPORT RIG
This rig is used to measure the fracturability of snack foods and potato by means of a
penetration test.
A 0.25" diameter spherical probe moves down onto a sample, which is centrally located over a circular
support, up to the point of fracture to give measure of fracturibility.

78. Pratik Potadar will present further

79. Distance Measuring Instruments
Linear measurement
Area measurement
Volume measurement

80. Linear Measuring Instruments
• Number of simple testing apparatus that are based upon distance
measurements are known
 Consistometer - Distance of catsup and puree flow along a horizontal trough
 Plumit - Depth a cylindrical metal rod falls into sour cream and yogurt
 Ridgelimeter - sag of fruit jellies
 Ruler, Calipers, are other well-known measuring length instruments

81. Bostwick consistometer
• Used to determine the
consistency of semi-liquid or
viscous foods e.g. sauces,
ketchup, puree
• Not suitable for non-pureed
foods
• A trap-door hold the sample and
prevent it from flowing
• Then, trap-door is immediately
opened
• Sample will flow along the
container

82. • First compartment dimensions : 5x5x3.8 cm
• separated from the second compartment by
means of a spring-loaded gate
• Second compartment dimensions : 5 x 24 x 2.5
• Floor has linings at 0.5-cm intervals
• Weighs about 800 g
• Example :
• Grade A & Grade B ketchup :- 9 cm
• Grade C ketchup :- 14 cm

83. Hilker- Guthrie Drop
• Measures the consistency of
semi-solid samples e.g.
cream, yoghurt
• An aluminum tube is dropped
onto the sample
• A scale on the aluminum tube
allows the determination of
distance penetrated by the
tube into the sample
• The more viscous the sample
is, the lesser the penetration

84. • Hollow aluminum tube:- Dia = “0.5”
Length = 4.5”
Lower end taper = 0.125”
Weight = 15 g
• Series of inscribed lines numbered 1 to 10
@ 0.375” intervals
• Mounted 12” from the surface of the
product.
• Released and allowed to fall in product
• Depth of penetration measured after 5
seconds
• Customary to take mean of 3 tests
• Scale:
• 0-2 = Very Thin
• 2-4 = Thin
• 4-6 = Medium
• 6-7.5 = Good
• 7.5-8.5 = Slightly heavy
• 8.5-10 = Heavy
• >10 = Very Heavy

85. Ridgeli-meter
• Measures rigidity/stiffness (grade) of gels
e.g. pectin gel
• Simple but effective instrument
• Standard test used by the industry
• The jellies are poured into tapered glass
tumblers of dia = 1.75” at bottom , 2.5” at
top and Height = 3.125”
• Boiling jelly is poured into the jar until it is
1/2 in. above the top of the jar

86. • After standing for 20–24 h at 25 ± 3°C the tape is
removed
• Jelly tipped out onto a small square of plate glass
• Pointer of of dial moved to surface of jelly
• Repeat after 2 min.
• A jelly of ‘standard firmness’ has a sag of 23.5%

88. Haughmeter
• Used to measure the quality of eggs
• Consists of a tripod stand
• Pin is present at centre which can be
moved up and down by screw
• Principle : High thickness albumen
indicates good quality

90. • Operation :
- Weighing of egg
- shell is broken gently and
- Egg is spread out on a horizontal glass plate.
- Placed such that the center pin is over egg
white about 10 mm out from yolk.
- Screw is turned until the face of the pin just
touches the albumen.
- The gauge measures the height of the
albumen above the plate.
Haugh units =100 log H
Where, H = albumen height ,
mm
Haugh unit should be 72 or higher for grade AA
Where,
G= 32.2
W= Weight of egg, gm

91. USDA consistometer
• Developed by United States Department of
Agriculture (USDA)
• Consists of a thin flexible plastic sheet over which
the product flows.
• Receptacle holding the food D = 3” & H = 3.25”
• Samples are placed on a sheet with several concentric
circles drawn and divided into quarters
• After 1 minute, distance of flow is measured in all 4
quarters and averaged

92. • Experiment :canned applesauce
• Readings taken at edge of applesauce
• For,
• grade A – Not greater than 6.5
• Grade B - Not greater than 8.5

93. 1. Penetrometer
• Consists of a cone and vertical shaft
assembly that is allowed to sink into a solid
fat by virtue of gravity
• Principle of the SURDD tester
• Cone penetration on solid fats
C = KW/P^(1.6)
- C = yield value of the product
- K =a constant whose value depends on the
cone angle = ( 𝐶𝑜𝑡2
α.cot α )/π
- W = weight of cone assembly, gm
- P = penetration depth after 5 s

94.  Ball indenter
Steel ball is pressed onto the material with a
constant force for a given time,
Removed and the diameter of the impression
measured
H = Hardness index in kg/ sq. cm
P = Penetration depth
 D = Diameter of ball, mm
 d = diameter of impression in material
Firmness of butter

95. • When dry, mature peas that have been soaked and
cooked are bounced off an inclined surface
• Horizontal distance they rebound is a function of
elasticity coefficient and is related to textural
quality
• Firm peas bounce farther than soft peas.
Where,
v =
Ф = angle at which pea leaves the plate
α = angle of the plate to the horizontal
u = the velocity of pea just before hitting the plate
e = coefficient of elasticity of the pea
h = height of the point of impact above the
collecting box
2. Rebound Distance

96. • Change in height or diameter of a food
under the application of a force.
• Measured sensorially by squeezing the
food in the hand.
• One of the methods of measuring the
‘firmness’ of a commodity.
3. Deformation

97. • The application of force F to three ideal
commodities gives deformations f, m,
and s, respectively, for the firm, medium,
and soft product.

98. • Most common types of force–
deformation curves hat are found on
foods.
• Majority of products give an A type
curve that is concave downward (soft
foods)
• B type curve is found with rigid
products such as firm green fruits and
vegetables, hard candy, and eggs in the
shell.
• C type curve, which is S shaped, is
found with breads, cakes and other
highly aerated deformable foods
• a1/a2 > F1/F2
• b1/b2 = F1/F2
• c1/c2 < F1/F2

99. • A sound speaker which is the is
placed in contact with a food and
caused to produce sound
• The frequency of the vibration is
gradually increased from a low to a
high value
• A microphone placed in contact with
the food at a position 90° to the
driver acts as a detector
• Equipment plots the amplitude of
vibration within the food as a function
of the driving frequency
3.1 Deformation by Acoustics

100. • If the food is in the shape of a uniform
cylinder, Young’s modulus can be
calculated from the resonance frequency
• ρ= Density
• f = frequency
• L= Lenghth

101. • Small irregularities in the surface
can give large errors in
deformation.
• In universal testing machine a
‘trigger force’ can be installed in
the PC program that starts the
measurement of compression
distance when the trigger force is
reached.
3.2. Geometry of the Test Specimen

102. • Change in diameter of a
horizontal cylinder under
compression :
• P = the force per unit length
• V = Poisson’s ratio
• E = Young’s modulus
• Change in diameter(Deformation) of a sphere
between flat plates
• F = the force
• k = constant
• E = Young’s modulus
• R = Radius

103. • To determine the flow properties
• provides an inexpensive, quick, easy and
effective way to measure the yield stress of high
density suspensions.
• A hollow cylinder is placed on a horizontal
surface
• Filled level to the top with the food, then the
cylinder is gently removed
• The food is allowed to flow out in a horizontal
direction under the force of gravity.
• Height or Diameter is measured
4. Slump Test

104. • Yield stress range 30–800 Pa
• Yield stress =
s’ = dimensionless slump value
=(original height - slump height) /
original height
 Slump test of a Bingham solid :
h0 = height of unyielded portion after
the slump

105. Gravity Current Flow
• A fluid that is released and allowed to flow under the
influence of gravity primarily in a horizontal direction over a
solid surface or another fluid of higher density is called
‘gravity current flow.’
• Consistometer measures the thickness of tomato purees
and similar products
• Three flow regimes have been identified in gravity currents-
(1) Inertial regime: Occur at very short times where the forces
of inertia and gravity predominate.
(2) Viscous regime: Occur at intermediate times where flow is
determined by the balance of viscous and gravity forces.
(3) Surface tension regime: Occur at long times where
viscous forces are balanced by surface tension forces.

106. • Bostwick Consistometer:
Where,
L- Length of gravity current
EV-Similarity value = 1.41
g- gravitational constant
q- Fluid volume per unit width
v- kinematic viscosity
T- time
• The flow of fluids in the Bostwick Consistometer can be modeled as a gravity
current

107. Area Measuring Instruments
• Several consistometers such as USDA Standard Consistency Tester
measure the flow of a fluid or semifluid food from a circular container out
across a horizontal plate and the diameter is measured at two points at right
angles.
• This is a distance measurement rather than area but is close to area
measuring instruments.

108. Particle Size Distribution
• Analysis of particle size distribution of particulate foods by sieving is
primarily based on area.
• Particulates with a cross-sectional area less than the screen aperture
fall through whereas those too large are retained.
• Most sieves are made with woven wires and have rectangular
apertures.
• The sieve number is based on the number of wires per linear inch.

109. Volume Measurement
Loaf Volume Meter
Measures the loaf volume
Succulometer
Measure the volume of juice that can be pressed
from fresh sweet corn and is used as an index of
maturity and quality.

110. Loaf Volume Meter
• This apparatus consists of a metal box connected
through a rectangular chute to a hopper containing
rapeseed.
• Loaf of bread is placed in the box, which is closed,
a slide in the chute is pulled out, and the rapeseed
is allowed to fill the box.
• Size of Box: 5.625 x 11.625 in for 1lb loaf of bread
and can read volumes between 1675 and 3000cm3

112. Succulometer
• 100-g sample of cut corn is placed and pressure is
applied through a hydraulic ram.
• A pressure of 500 lb is maintained for 3 min and the
juice that flows out is collected in a 25-ml graduated
cylinder.
• Succulometer values to quality of sweet corn as
follows:
 Fancy quality, more than 22 ml of juice;
 Extra standard, 19–22 ml;
 Standard, 12–18 ml;
 Substandard, less than 12 ml.

113. Time Measuring Instruments
• Measure the time for a standard volume
of fluid to flow through a restricted
opening.
Kinematic
viscometers
• Measure the time for a ball to fall a given
distance through a liquid
Falling-ball
viscometers

114. Kinematic viscometers

115. Falling-ball viscometers

116. Work, Energy, and Power Measuring Instruments
• Energy and work both have the dimensions mass ×length2×time-2.
Work = force x distance
• Instruments that plot out the force–distance relationship of a test can
provide work functions by measuring the area under the force –distance
curve.
• There are two work elements in a compression– decompression cycle.
(1) The area under the curve during compression represents the work
done on the food by the machine.
(2) The area under the curve during decompression represents the
work returned to the machine by the food as it recovers.

117. Ratio Measuring Techniques
• This is not a widely used technique.
• The numbers obtained are dimensionless since they are derived from the
ratio of two measurements of the same variable.
• The Texture Profile Analysis parameter of cohesiveness is a ratio because
cohesiveness is defined as

118. Miscellaneous Methods
The criteria for inclusion under this heading are
(a) An objective method,
(b) Measurement correlates well with texture, and
(c) Method does not fit into any of the categories described
previously

119. Optical Methods
• The cell fragility method is an optical method that is used to
measure the toughness of fish.
• In this method a standard weight of fish is homogenized in a
blender in a mixture of 2% trichloroacetic acid plus 1.2%
formaldehyde for a standard time after which the optical density is
measured.
• Tender fish grind into a fine state and give a high optical density
whereas tough fish remain as fewer large particles and give a
lower optical density.

120. Sound
• Drake (1963, 1965) analyzed the amplitude and duration of
chewing sounds over a wide range of frequencies.
• Christensen and Vickers (1981) reported that loudness of chewing
sounds correlated highly with sensory crispness and the high
correlation was maintained even when a 100 decibel masking
noise was used as an auditory block.
• Sounds are occasionally used to judge the quality of foods other
than crisp or crunchy.

121. Ultrasound Tests
• This section introduces the use of ultrasound with frequencies
higher than can be perceived by the ear (>16 kHz)..
• The velocity of propagation of a compressional ultrasound wave in
a solid material is described by the equation

122. Rollability
• Simple semi quantitative method for measuring the textural quality of
tortillas.
• It consists of wrapping a tortilla around a 1.0 cm diameter wooden cylinder
(dowel) and then subjectively rating the tortilla for cracking and breakage
on a five-point scale.
• The rollability scale is:
1 no cracking (best quality)
2 signs of cracking but no breaking
3 cracking and breaking beginning on one surface
4 cracking and breaking imminent on both surfaces
5 unrollable, breaks easily

123. Electromyography
• Small electrical currents are present in muscles when they contract.
• By attaching electrodes to the skin in the appropriate location it is
possible to measure the electrical activity of muscles that are near
the surface of the body.
• A plot of magnitude of the electrical current versus time is called an
electromyogram (EMG).
• It is a relatively simple method for measuring muscle activity
because it is not invasive or obtrusive and the attachment of the
electrodes to the face does not interfere with normal masticatory
behavior.

124. Electropalatography
• Records tongue movement during eating and swallowing and its
applicability to study differences in texture.
• EPG consists of artificial palate embedded with 62 electrodes that cover the
entire artificial palate
• Contact patterns into three phases:
Phase 1-an approach phase when the number of EPG contacts increased
Phase 2- a period of full contact between the tongue and 62 electrodes
Phase 3- a release phase when the number of contacts decreased.

125. Electropalatography

126. Imperfect Lubricated Squeezing Flow
• This test procedure is characterized by an outward and upward flow of
a liquid or semiliquid in a shallow container when compressed at a
constant rate under a wide plate.
• It shows promise for measuring the viscous properties of spreadable
foods such as peanut butter and cheese spreads that are difficult to
handle in rotational viscometers

127. Pendulum Impact Test
• Izod pendulum test, that is a well-known test for materials of
construction to measure the breaking strength of rape seed
pods.
• A pod is clamped in a vertical position directly under the pivot
of a pendulum.
• A pendulum of adjustable mass and length is pulled back a
fixed angle, released, and allowed to strike and break the pod.
• The angle the pendulum swings up after the impact is
measured by an optical encoder and PC.
• The rupture energy required to snap the pod is measured by
the reduction in the angle of the upswing after snapping a pod
compared with the upswing angle when no pod is present.

129. Multiple Measuring Instruments
FTC Texture Test System
Universal Testing Machines (UTM)

130. FTC Texture Test System

131. Universal Testing Machines (UTM)
• This instrument is used to analyze texture.
• Measures the change of force
• Now advanced machine are connected to
computer
• Can be attached with various probes

133. Advantages of UTM
1. Measures different kinds of
tests
2. Gives complete force plot,
giving all the changes that occur

134. Instron
TA.XT2 Texture
Analyzer
QTS Texture
Analyzers
Lloyd Texture
Analyzer
UTM

135. Instron
• The Instron Corporation make a wide
range of UTMs for a wide range of
products, most of which are nonfood.
• Max force capacity of 50,000N.
• It has a force capacity of 500 N and
crosshead speeds cover the range 0.05–
1000 mm min-1.
• A wide range of accessories are available
for food texture analysis including
fixtures for the Kramer Shear Press.

137. • Stable Micro Systems, and their US Distributor,
Texture Technologies Corp., have developed
an extensive library of food applications.
• The standard TA.XT2 Texture Analyzer is a
single screw machine that was developed
especially for food work.
• It has a force capacity of 250 N and crosshead
speeds of 6–600mm min-1.
• The TA.XT2 Plus model offers speeds up to
2400 mm min-1.
TA.XT2 Texture Analyzer

139. QTS Texture Analyzers
• This line of single-screw machines was
developed from concepts originally
established by the Leatherhead Food
Research Association in the United
Kingdom as the Stevens Texture Analyzer.
• It has a force capacity of 250 N and
crosshead speeds from 5 to 1000mm min-1
in 1 mm increments.
• A number of accessories for food
applications are available.

140. • A number of accessories for testing
foods can be attached to Lloyd
machines.
• The commonly used basic machine is
the model TA500 which is chain driven
• Force capacity of 500 N and speed
range of 1–1000 mm min-1
Lloyd Texture Analyzer

142. Texture Profile Analysis (TPA)
• Double compression test for
determining the textural
properties of foods.
• The TPA test was often called
the "two bite test" because the
texture analyzer mimics the
mouth's biting action.

143. Decoding TPA results
Mechanical
Parameter
Meaning
Fracturability First significant break in the curve
Hardness Force exhibited in first bite at maximum compression
Cohesiveness Ratio of positive areas under first and second compression (A2/A1)
Adhesiveness Work required to pull the plunger away after first compression (A3)
Springiness Ratio of lengths of compression in the 2nd and 1st plunge. (L2/L1)
Stringiness Distance for which product is extended during decompression before
separation of probe
Gumminess Hardness * Cohesiveness
Chewiness Gumminess * Springiness

145. Dimensional Analysis of TPA Parameters
Mechanical
parameter
Measured
variable
Dimensions of
measured variable
Hardness Force MLT-2
Cohesiveness Ratio Dimensionless
Springiness Ratio Dimensionless
Adhesiveness Work ML2T-2
Fracturability
(brittleness) Force MLT-2
Chewiness Work ML2T-2
Gumminess Force MLT-2

146. THANK YOU