DocumentTe

‘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 perception.

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

http://www.alibaba.com/catalog/10999219/Frozen_Strawberry_IQF/showimg.html

• Texture

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

http://en.wikipedia.org/wiki/Somatosensory_system

• 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, crunchyButter SoftToffee GummyMeat/ Paneer ChewyBiscuit BrittleRasogolla SpongyOranges JuicyChest nut puree PastySemolina GrainySalt Gritty/ coarsePeanut butter, Creamysoup, 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

• 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 popularway 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.

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

• Known as the “two bite test”

• Provides textural parameters which correlate well withsensory evaluation parameters

TPA (TEXTURE PROFILE ANALYSIS)




FO

RC

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TIME

FIRST BITE




FO

RC

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TIME

SECOND BITE

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TPA (TEXTURE PROFILE ANALYSIS)Movement of the Probe

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TPA (TEXTURE PROFILE ANALYSIS)Movement of the PROBE

DOWN

‘COMPRESSION’

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UP

‘Decompression’

DOWN

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UP

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Analysis of the data

Fracturability

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TPA (TEXTURE PROFILE ANALYSIS)Analysis of the data

Fracturability DefinitionThe force at which there isthe first significant break inthe curve (originally calledthe brittleness)

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Hardness 1Hardness 2

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Hardness Hardness 2

DefinitionThe maximum force duringthe first cycle of compression.Is also known as the“firmness”.

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A B

Area 1

Area 2

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A B

DefinitionThe ratio of the positive forcearea during the second cycleof compression to that of thefirst cycle.

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A B

DefinitionThe ratio of the positive forcearea during the second cycleof compression to that of thefirst cycle.

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A B

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Stringiness

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Stringiness

NoteDefined as the distance that theproduct is extended during de-compression before separatingfrom the probe.

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Springiness

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Analysis of the data

Springiness

DefinitionThe height that the foodrecovers during the time thatelapses between the end of thefirst cycle and the start of thesecond cycle.

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Springiness

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Work of Adhesion

Adhesivness

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DefinitionThe negative area forthe first compression cycle - representing the work neededto overcome the attractiveforces between the surfaces ofthe probe and the food.

Work of Adhesion

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Definition

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 analyserStable Micro Systems, TA-XT2i

Different probes

Needle probe Compression Cylindrical probe Three point bend rig

platens

Cylinder probe

• 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

FirmnessButter,

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

SpreadibilityButter, 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 methodsA 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 panelDisadvantages• Consensus method means risk of bias from dominant

personality• Danger of lack of consistency and reproducibilityTexture 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.

http://www.sensorysociety.org/ssp/wiki/Principal_Component_Analysis/

• 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

Thank You!