Texture Analysis of Raw and Processed Food products

‘Textural Analysis- Machine
and Human Perspectives’
Vinita Puranik and
Vandana Mishra
Centre of Food Technology,
University of Allahabad

Sensory Evaluation
A scientific discipline used to evoke, measure, analyze
and interpret reactions to those characteristics of food and
materials as they are perceived by senses of sight, smell,
taste, touch and hearing.
IFT; USA
In order to receive information from the environment we are
equipped with sense organs eg eye, ear, nose, skin.
Each sense organ is part of a sensory system which receives
sensory inputs and transmits sensory information to the
brain.

Why sensory science?
• Sensory science shows the way in product
development and Quality Control
• ‘It is like Braille to the blind’.
Why is sensory evaluation important in product
development?
• Many decisions must be reached during the
development of a product. All these decisions
will influence the final product attributes or –
characteristics.

• A group of similar sensory impressions
mediated by a given organ is referred to
as sense (modality).
• Factors from the environment or from
body biochemistry that elicit sensory
impression are referred to as sensory
stimuli
• A combination of sensory impressions is
called a sensation.
• An interpretation of sensation with
reference to what has been experienced
and learned by individual and the resultant
overall impression is called sensory

FOOD PRODUCTS ARE MULTIDI-
MENSIONAL:
• Visual: package appearance, product
appearance, color.
• Olfactory: product aroma/fragrance.
• Kinesthetic/Tactile: product feel.
• Gustatory: product taste, texture.
• Auditory: sound from use.

Sensory Characteristics
• Appearance
• Taste
• Odor
• Flavor
• Texture
• Sound

• Texture
It refers to the properties held and sensations
caused by the external surface of objects
received through the sense of touch.

• Texture can be regarded as a
manifestation of the rheological
properties of a food. -
It is an important attribute in that
it affects processing and handling
affects shelf-life and consumer
acceptance of foods.

Characterisation of food texture commonly falls into two main
groups, based on
 sensory and
 instrumental methods of analysis.
• Sensory Evaluation of food texture by touch includes the
use of the fingers, as well as the lips, tongue, palate and
teeth in the mouth.
• Instrumental methods of assessing food texture
 can be carried out under more strictly defined and
controlled conditions and
 Analysis gives consistent results, if analysed in constant
condition.
 Instrumental procedures are generally more sensitive and
reproducible than their subjective sensory equivalents
where variation in results is generally attributed to variation
in sample heterogeneity rather than instrumental precision.

Texture
– Qualities felt by tongue, palate, teeth,
or fingers
Texture – mouthfeel – how a food feels in your
mouth (sticky, smooth, tender)
Tactual and mouth feel play an important role in examining the body and
texture characteristics. –
-The tongue and palate evaluate feeling of meatiness and grittiness in butter
and sandy defect in ice cream and sweetened condensed milk.
-The pressure between the teeth and jaws determine the hardness, chewiness
and gumminess.
-The fingertips and ball of the thump help in determining other textural
attributes, notably stickiness, elasticity/ sponginess and brittleness.
-Creamy was as a mouthfeel characteristic``possessing the textural property
producing the sensation of the presence of a miscible, thick, smooth liquid
in the oral cavity''.

Food product Textural attribute most
commonly associated
Carrot (raw) Hard, crunchy
Butter Soft
Toffee Gummy
Meat/ Paneer Chewy
Biscuit Brittle
Rasogolla Spongy
Oranges Juicy
Chest nut puree Pasty
Semolina Grainy
Salt Gritty/ coarse
Peanut butter, Creamy
soup, and
most dairy products

Nature of Attribute Examples
Visual Colour (Fruits and Vegetables)
Dropping rate (Liquids)
Auditory sound intensity during mastication
(Crunchy, Crispy Foods)
Tactile, Non oral Resistance to deformation (Fruits and bread)
Resistance to cut with a knife (meats)
Resistance to cut with a spoon (Dairy deserts)
Tactile, Oral Resistance to mastication (Solid Foods)
Resistance to displacement in mouth (Liquid Foods)
Structural Characteristics (fibrousness, granularity, flouriness etc.)
In mouth movements (liquids and Solids)

• Texture analysis is primarily concerned with the evaluation
of mechanical characteristics where a material is subjected
to a controlled force from which a deformation curve of its
response is generated.
• Texture analysis is the science used by food technologists
to objectively measure the subjective mechanical
characteristics of finished foods, their intermediate
components and functional ingredients.
• In simple terms, we use instruments to measure how a
food feels when we eat it or performs during
processing or handling.
• Instrument must have the capacity to measure
certain characteristics with a type and intensity
similar to those perceived by the human mouth.

Instrumental techniques involves
measurement
• Fundamental tests
• Empirical tests
• Imitative tests
"Pictures used with permission of Stable Micro Systems Ltd.,
Godlaming, UK"

• Fundamental tests determine one or more physical
constants to describe exactly the properties of the
food in terms of well defined rheological parameters.
• Empirical tests usually measure parameters which are
poorly defined in rheological terms but which, from
practical experience, have been found to relate closely
to the property of interest.
• Imitative tests, aims to reproduce the mechanical
operations applied in human evaluation to mimic our
senses to make the test as applicable to the product
as possible, for example, to represent a biting action
or a chewing action.

Researchers seek correlation between
sensory and instrumental measurements:
1) the need for quality control instruments
2) the desire to predict consumer response
3) the desire to understand what is being
perceived in sensory texture assessment
4) the need to develop improved / optimised
instrumental test methods and, ultimately,
to construct a texture testing apparatus that
will duplicate the sensory evaluation.

Texture Profile Analysis
A closer look at this popular
way of characterising the
structure of foods

• Texture profile analysis (TPA) is an
objective method of sensory analysis
pioneered in 1963 by Szczesniak.
• Later in 1978 Bourne adapted the Instron
to perform TPA by compressing standard-
sized samples of food twice.
"Pictures used with permission of Stable Micro
Systems Ltd., Godlaming, UK"

The test consists of compressing a piece of food two times in a
reciprocating motion that imitates the action of the jaw and
extracting from the resulting force-time curve a number of
textural parameters that correlate well with sensory evaluation
of those parameters.
The mechanical textural characteristics of foods can be divided
as-
 Primary parameters of
• Hardness,
• Cohesiveness,
• Springiness (elasticity),
• Adhesiveness, and
 Secondary (or derived) parameters of
• Fracturability (brittleness),
• Chewiness
• Gumminess
• Resilience
• Stringiness
• Initial Modulus

Texture Analysis of Raw and Processed Food products

• Known as the “two bite
test”
• Provides textural
parameters which correlate
well with
sensory evaluation
parameters
TPA (TEXTURE PROFILE ANALYSIS)

• Known as the
“two bite test”
parameters which
correlate well with
sensory
evaluation
parameters
FORCE
TIME
FIRST BITE

• Known as the
“two bite test”
parameters which
correlate well with
sensory
evaluation
parameters
FORCE
TIME
SECOND BITE

Force
Time
o
Movement of the Probe

Force
Time
o
Movement of the PROBE
DOWN
‘COMPRESSION’

Force
Time
o
UP
‘Decompression’

DOWN
Force
Time
o

UP
Force
Time
o

Force
Time
o
TPA (TEXTURE PROFILE
ANALYSIS)
Analysis of the data
Fracturability

Force
Time
o
Fracturability Definition
The force at which there is
the first significant break in
the curve (originally called
the brittleness)

Force
Time
o
Hardness 1
Hardness 2

Force
Time
o
Hardness
Hardness 2
Definition
The maximum force during
the first cycle of compression.
Is also known as the
“firmness”.

Force
Time
o
A B
Area 1
Area 2

Force
Time
o
A B
Definition
The ratio of the positive force
area during the second cycle
of compression to that of the
first cycle.

Force
Time
o
A B

Force
Time
o
Stringiness

Force
Time
o
Stringiness
NoteDefined as the distance that the
product is extended during de-
compression before separating
from the probe.

Force
Time
o
Springiness

Force
Time
o
TPA (TEXTURE PROFILE
ANALYSIS)
Springiness
Definition
The height that the food
recovers during the time that
elapses between the end of the
first cycle and the start of the
second cycle.

Force
Time
o
Work of Adhesion
Adhesivness

Force
Time
o
Definition
The negative area for
the first compression cycle -
representing the work needed
to overcome the attractive
forces between the surfaces of
the probe and the food.
Work of Adhesion

Force
Time
o
Definitio
n
The maximum negative force
of the first compression cycle
Adhesivness

Resilience
 Not an original TPA parameter.
 Developed from looking closely at elastic recovery
 A measurement of how the sample recovers from
deformation both in terms of speed and forces
derived. .
 Ratio of the first UP ( decompression) stroke to the
first DOWN ( compression) stroke
• It is taken as the ratio of areas from the first probe
reversal point to the crossing of the x-axis and the
area produced from the first compression cycle.
• It is not a parameter from the original Texture Profile
Analysis work but instead has developed from
looking more closely at the elastic recovery of the
sample.
• There are no units for this parameter.

Initial Modulus
 Not an original Texture Profile Analysis parameter
 Developed from looking closer at curve before fracture
 Initial Modulus = Initial Stress / Initial Strain
 Initial Stress: taken as mean force from 0.5 -1.5secs and then dividing
by the Contact Area
 Initial Strain: calculated at the 1.5 second point
 Initial Modulus is derived as Initial Stress / Initial Strain.
 Units are in e.g. N/mm².
 The Initial Stress is calculated as the average force of the points in the
range 0.5 seconds to 1.5 seconds divided by the Contact Area (which is
specified by you in the Run A Test screen).
 Initial Strain is the strain calculated at the 1.5 second point of the curve.
The Initial Strain can only be calculated if STRAIN is available and
hence PRODUCT HEIGHT can be derived.
 Initial Modulus is not a parameter from the original Texture Profile
Analysis work but instead has developed from looking more closely at
the portion of the curve before fracture.

Texture profile parameters are
determined from:
• Fracturability = F1
• Hardness = F2
• Cohesiveness = A2/A1
• Adhesiveness = (based on)
A3
• Springiness = D1
• Gumminess = hardness x
cohesiveness
= F2 x A2/A1
• Chewiness = hardness x
cohesiveness x
springiness
= F2 x A2/A1 x D1
• Modulus of deformability
(based on) slope, S1

• Hardness is defined as the force required to cut through a Food sample
using the front teeth or as the maximum peak force during the first
compression cycle (first bite) and has often been substituted by the term
firmness. Units are kg, g or N.
• Fracturability (originally called brittleness) is defined as the force required to
break a Food sample into piece or the force at the first significant break in
the TPA curve. Brittleness, crunchiness, and crumbliness, which are a
similar concept, can be measured as the ease with which the material
fractures under an increasing compression load; in general, the smaller the
deformation under a given load, the lower the cohesiveness and the greater
the ability to fracture of the product. Units are kg, g or N.
• Adhesiveness is defined as the force with which a cooked Food adheres to
other materials. e.g., tongue, teeth, palate, fingers or as the negative force
area for the first bite and represents the work required to overcome the
attractive forces between the surface of a food and the surface of other
materials with which the food comes into contact, i.e. the total force
necessary to pull the compression plunger away from the sample. For
materials with a high adhesiveness and low cohesiveness, when tested, part
of the sample is likely to adhere to the probe on the upward stroke. Units are
kg s, g s or N s.

• Cohesiveness is defined as the force of internal bond holding a
Food structure or the ratio of the positive force area during the
second compression to that during the first compression.
Cohesiveness may be measured as the rate at which the
material disintegrates under mechanical action. Tensile
strength is a manifestation of cohesiveness. If adhesiveness is
low compared with cohesiveness then the probe is likely to
remain clean as the product has the ability to hold together.
Cohesiveness is usually tested in terms of the secondary
parameters brittleness, chewiness and gumminess.
• Springiness (originally called elasticity) is the extent to which a
piece of Food returns to its original length when stretched or is
related to the height that the food recovers during the time that
elapses between the end of the first bite and the start of the
second bite.
• Gumminess is defined as the product of hardness x
cohesiveness. Gumminess is a characteristic of semisolid foods
with a low degree of hardness and a high degree of
cohesiveness. (N)

• Chewiness is defined the length of time required to masticate Food to a
state of swallowing or the product of gumminess x springiness (which equals
hardness x cohesiveness x springiness) and is therefore influenced by the
change of any one of these parameters. Chewiness, tenderness and
toughness are measured in terms of the energy required to masticate a solid
food. They are the characteristics most difficult to measure precisely,
because mastication involves compressing, shearing, piercing, grinding,
tearing and cutting, along with adequate lubrication by saliva at body
temperatures. It should be understood that the same product cannot exhibit
both chewiness and gumminess, unless as a solid it becomes a semisolid
during sensory mastication. Such a transition is practically never
accomplished during instrumental TPA evaluation. Thus, it is incorrect to
quantify and report chewiness and gumminess in TPA of solid or semisolid
products. Chewiness should be reported for solids and gumminess for
semisolids. (J)
• Stringiness is the distance the product is extended during decompression
before separating from the compression probe. It is not a parameter from
the original Texture Profile Analysis work but instead has developed from
looking more closely at the adhesiveness portion of the curve. The units of
this parameter would be in distance e.g. mm.

Texture analyser
Stable Micro Systems, TA-XT2i
Godlaming, UK"

Different probes
"Pictures used with permission of Stable Micro
Systems Ltd., Godlaming, UK"

"Pictures used with permission of Stable Micro Systems Ltd., Godlaming, UK"

Cylinder probe

• "Pictures used with permission of Stable
Micro Systems Ltd., Godlaming, UK"

Godlaming, UK"

• Stress relaxation describes how polymers relieve stress under
constant strain, because they are viscoelastic. This
nonlinearity is described by both stress relaxation and a
phenomenon known as creep which describes how polymers
strain under constant stress.
• Creep is the tendency of a solid material to slowly move or
deform permanently under the influence of stresses. It occurs
as a result of long term exposure to levels of stress that are
below the yield strength of the material. Creep always
increases with temperature.
• Compliance can mean in mechanical science the inverse of
stiffness.
• Creep recovery is rate of decrease in deformation that occurs
when load is removed after prolonged application in a creep
test. Constant temp. is maintained to elliminate effects of
thermal expansion and measurements are taken from time
load is zero to eliminate elastic effects.

Penetration test Principle Food tested Probe used
Firmness
Butter,
Margarine
cylinder probe, conical probe,
TTC spreadibility rig
cheese spread TTC spreadibility rig
Mayonnaise TTC spreadibility rig
Hardness Caramel Spherical probe
Chocolate bars cylinder probe
Icecream cylinder probe
Softness Cheese, Cream cylinder probe, conical probe
Stickiness Caramel Spherical probe
cheese spread TTC spreadibility rig
Stringiness Caramel Spherical probe
Spreadibility
Butter, cheese
spread, TTC spreadibility rig
Jam, Marmalade TTC spreadibility rig
Skin strength/Elasticity Grape cylinder probe
Gel strength/
adhesiveness Jam, Marmalade cylinder probe

Compression test
Principle Food tested Probe used
Firmness Cake cylinder probe
Noodles cylinder probe
Hardness Carrot cylinder probe
Breaking force (shell
strength) Egg whole cylinder probe / Flat blade
Bending test Principle
Firmness Carrot 3 point bend rig
Uniaxial Tension Test
Principle
Resistence to extension /
Extensibility Gluten Kiefer Dough extensibility rig
Noodles Kiefer Dough extensibility rig

Descriptive analysis in sensory
Evaluation
• “Descriptive analysis is the sensory method by
which the attributes of a food or product are
identified and quantified using human subjects
who have been specifically trained for this
purpose”.
• It is the most complex and most sensitive of the
sensory evaluation tools available.
• It provides a qualitative, detailed description of
the sensory attributes perceived in a product as
well as a qualitative measurement of the
magnitude or intensity of each attribute
detected.
• Many different types of Descriptive Analysis
methods exist.

Common descriptive methods
A variety of procedures have been
developed for descriptive testing. These
include
• Flavour profile
• Texture profile
• Quantitative descriptive analysis (QDA)
• Spectrum analysis
• Time-Intensity descriptive analysis
• Free choice profiling

Flavour profile
• Uses panel of 4 - 6 trained panellists
• Panel sit round table and evaluate one sample at a time
and record the ratings
• Panel then discusses ratings and arrives at a consensus
• Advantage of small panel
Disadvantages
• Consensus method means risk of bias from dominant
personality
• Danger of lack of consistency and reproducibility
Texture profile
• Procedure similar to flavour profile, but a wider range of
scaling techinques may be used
• Results may be by consensus method or by statistical
analysis
• Panel training involves understanding underlying
mechanical principles
• Experience of a wide range of textural attribute

Quantitative descriptive analysis
• Panelists develop agreed terminology
beforehand
• Panelists evaluate products one at a
time in separate booths
• Panellists are discouraged from
discussing results afterwards
• Scoring is by marking on a line
• The results are analysed statistically
• Can lead to inconsistency of results

Spectrum descriptive analysis
• Panelists score intensities with respect to learned
absolute intensity scales
• A wide variety of standard descriptors are provided
• Scoring is both by use of descriptive terms and by
marking on a line
• It is intended to provide consistent and reliable data by
providing a wide range of standards
Time-intensity analysis
• Panelists evaluate intensity of an attribute at intervals
over a period
• Time-intensity response curve is generated
• This should not be seen by the panelists while it is being
generated
• Requires a well-trained panel to be effective

Free-choice profiling
• Panelists are allowed to invent their own terms to describe the sensory
attributes of a set of samples
• Samples are from the same category of products
• Panelists develop their own scoresheets
• Multivariate statistical methods are used to analyse the data
• These are aimed at identifying terms that appear to measure the same
attribute
• Panel training requirements are minimal
• Panel is closer to a consumer panel
• Still being evaluated against other descriptive methods.
Free-choice profiling (FCP) is a quick and inexpensive method in which
consumers are asked to both identify attributes in the sample and rate
the liking and/or intensity of those attributes.
• They should be provided with adequate instruction on how to perform
this test and possibly given product categories to consider (aroma,
appearance, flavor, texture, etc.).
• Each consumer will have different attributes, indicating which are
most important. Though consumers should be recruited as normal
(product usage, age/gender specifications), researchers may be able to
separate consumers into groups, better identifying which
characteristics are most important in that segment.

FCP Analysis
• Since consumers will have developed different lexicons/vocabularies, similar
terms may be grouped at the researcher’s discretion: first by category, then
by term. It is important to note that consumers may use terms in different
ways.
• Generalized Procrustes Analysis (GPA) is a common statistical tool to
analyze FCP data. GPA can compare FCP results across all terms. Values
remain as individual data, not mean values. Results will indicate significant
attributes, product discrimination and panelist performance.
• Principal Component Analysis (PCA) on product attributes may also be used
to graphically represent product and panelist scores, though not as clearly
as GPA. The resulting descriptive data is decomposed using a multivariate
technique such as principal component analysis (PCA). This reduces the
number of sensory dimensions required to describe the product set.
Individual consumer scores are then integrated into the sensory space by
regressing each consumer's response onto the coordinates obtained from
PCA. Since the data analysis is on an individual not aggregated level, the
shortcoming of traditional product testing that assumes liking to be similar
across individuals may be overcome
FCP Benefits and Limitations.
• This method is quick, inexpensive and provides insight into consumer
perception not given by a descriptive panel or traditional consumer testing.
• They may be suitable to marketing promotions, provide a new direction for
product development or uncover unidentified product defects or
considerations. However, terms generated by consumers may be too
personal or difficult to interpret.

• Texture is regarded as a manifestation of the rheological
properties of a food and it affects processing, handling and
consumer acceptance of foods
• Texture analysis is the science to objectively measure the
subjective mechanical characteristics of foods.
• As the food industry changes in response to consumer
demands and expectations, the variety of products evolves
and grows, so all decisions from above analysis will influence
the final product attributes or characteristics.
• Researchers seek correlation between sensory and
instrumental measurements, so Instrument must have the
capacity to measure characteristics with a type and intensity
similar to those perceived by the human mouth.
Conclusion

Texture Analysis of Raw and Processed Food products

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