analysis of what is texture? food...

______ITP503- Analysis of Food Texture - PHA 2020 –Handoutsphariyadi.staff.ipb.ac.id

phariyadi.staff.ipb.ac.idITP503, 2020

Analysis ofFOOD TEXTURE(Analisis Sifat Rheologi Bahan Pangan Cair,Padat dan Semi Padat)

Purwiyatno Hariyadiphariyadi.staff.ipb.ac.id


Analysis of Food Texture

Resource :


Texture comprises those properties of afoodstuff, apprehended by the eyes and bythe skin and muscle senses in the mouth,including roughness, smoothness,graininess, etc.

(Anonymous, 1964)Anonymous. 1964. Sensory testing guide for panel evaluation of foods and

beverages. Prepared by the Committee on Sensory Evaluation of the Institute ofFood Technologists. Food Technol. 18, 1135–1141.

What is Texture?


What is Texture?

Texture is the attribute of a substanceresulting from a combination of physicalproperties and perceived by the senses oftouch, sight, and hearing.

Physical properties may include size, shape,number, nature, and conformation ofconstituent structural elements

(Jowitt, 1974)Jowitt, R. 1974. The terminology of food texture. J. Texture Stud. 5, 351–358.


Texture is the human physiological-psychological perception of a number ofrheological and other properties offoods and their interactions

(McCarthy, 1987)McCarthy, O. J. 1987. Large deformation testing of solid foods. Food

Technology in New Zealand July, 40– 43.

What is Texture?


• Physical properties = food structure• Group of mechanical and/or rheological

properties Feeled/sensed by touch, usually in mouth Not a chemical senses (taste/odor)

• Objective measurement through force [MLT-2],work [ML2T-2], and flow [L3T-1]

• “Texture” usually applies to solids;• “Viscosity” to liquids.

What is Texture?



Texture is associated with …

• Food rheology• Other physical properties:

wettability, phase changes, surfacetension

• Sensory science• Mastication/anatomy/physiology


• ButRheology and mechanical

properties are not textureEmpirical tests may do a

better job of predicting texture asperceived by panelists



“The fact that fundamentalrheological measurements may

not correlate as well withsensory measurements of

texture as do empirical testsmay result from the

incompleteness of the scienceof rheology to describe all the

changes that are actuallysensed in the mouth”

Malcolm Bourne (1982)



The importance of Texture:- Critical -- food in which texture is thedominant quality characteristic (meat, celery,chips)


The importance of Texture:- Important-- foods in which texture issignificant but not dominant (fruit, bread,candy)


The importance of Texture:- Minor -- foods in which texture makes anegligible contribution (beverages, thin soups)



Primaryparameters

Secondaryparameters

Popular terms

Hardness Soft – firm – hard

Cohesiveness BrittlenessChewinessGumminess

Crumbly – crunchy – brittleTender – chewy – toughShort – mealy – pasty – gummy

Viscosity Thin – viscous

Elasticity Plastic – elastic

Adhesiveness Sticky – tacky - gooey

Texture: Parameters & nomenclature(Bourne,2002)

Mechanical characteristics


Primaryparameters

Secondaryparameters

Popular terms

Particle size andshape

Gritty, grainy, coarse, etc

Particle shape andorientation

Fibrous, cellular, crystalline,etc.


Geometrical characteristics


Primaryparameters

Secondaryparameters

Popular terms

Moisture content Dry – moist – wet - watery

Fat content Oiliness

Greasiness

Oily

Greasy


Other characteristics


Texture Analyzers


• Liquid foods (viscosity)• Solid foods.

Texture of foods …


Liquid food viscosity

• Viscosity:a key property of liquids and ameasure of the resistance to flow.

• More energy required to make a viscousfluid flow than a non-viscous fluid.

• The viscosity of a solution increases non-linearly with polymer concentration.



[=] g cm-1det-1 = poise

1 poise = 100 cpExample :

Water (20oC, 1 atm) = 1.0019 cpWater (80oC, 1 atm) = 0.3548 cp

Air (20oC, 1 atm) = 0.01813 cp

C2H5OH (lq; 20oC, 1 atm) = 1.194 cpH2SO4 (lq; 25oC, 1 atm) = 19.15 cpglycerol (lq; 20oC, 1 atm) = 1069 cp

Liquid food viscosity

• Viscosity: µ


−µ=τ

dydv

−µ=

dydv

AF

: Hk. Newton

γ

τ

τ = gaya geser

Kemiringan = µ

γ=− γdydv

, laju geser (shear rate)

.

Liquid food viscosity:Newtonian Fluids


K : Indeks tingkah laku aliran (flow behavior index)n : Indeks konsistensi

τ= K (γ )n ...............> model “Power law”1

.

A. Newtonian [t = m (g )] “power law”, K=m dan n=1.

B. Pseudoplastikτ= K(γ )n, n<1.

C. Dilatanτ= K(γ )n, n>1

.

Liquid food viscosity:NON-Newtonian Fluids


.τ= τo + K (γ)n ...............> model “Herschel-Bulkley”2K : Indeks tingkah laku aliran (flow behavior index)n : Indeks konsistensiτo : gaya geser awal (yield stress)

A. Bingham plastikτ = τo + K(γ) .

τo

B. Fluida H - Bτ= τo + K(γ)n; n<1.

2

Liquid food viscosity:NON-Newtonian Fluids

.


Model Casson :1/2 = Ko + K1

1/2.

( )1/2.

1/2

Ko

Kemiringan = K1Apa pengaruh Ko thd

bentuk coklat?

Liquid food viscosity:Rheologi “Melted Chocolate”:


τo

00

τ

- du/dy = .

Viskositas??

Liquid food viscosity:Hubungan antara gaya geser vs. laju geser (gradienkecepatan) untuk fluida newtonian dan non-newtonian



τo

00

τ

- du/dy = .

Viskositas??



Dapat pula digunakan viskositas apparent (µapp)

µ app = µNewtonian

τµapp = γ.

Non-newtonianτ

µ app = = Kγn-1γ.


Viskositas??= f (γ)


Newtonian

app

.




Shear thinning

app

.



Shear thinning – tendency of some materials to decreasein viscosity when driven to flow at high shear rates,such as by higher pressure drops

Increasing shear rate


app

.



shear thickening– tendency of some materials to

increase in viscosity when driven toflow at high shear rates



Viskositas??= f (γ)= f (t)

Rheopectic: coklat, suspensi pati

Time independent

Thixotropik: madu, gum

t (time)

app



µapp = Aoe(Ea/RT) : Hubungan Arrhenius


Viskositas??= f (γ)= f (t)= f(T)

app

T (Temperature)


Ln µapp = ln Ao - Ea/RT

Kemiringan = Ea/R

Ln Ao


Viskositas??= f (γ)= f (t)= f(T)

ln app

1/T (Temperature-1)


Liquid food viscosity:The properties of the solution are conventionally split into three regions:read https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1861804/


Dilute Regime. The polymers act as isolated "particles"too dilute to interact with each other. They can beapproximated as spheres of radius rg (the Stokes radius -the smallest sphere that can contain the polymer)

Semi-Dilute Regime. The "particles" start to interactsignificantly because their total excluded volumeapproaches close packing. Further increase inconcentration leads to much greater overlap of polymercoils and rapid increase in viscosity.

Concentrated Regime. The individual polymer moleculesoverlap in a tangled mass. The viscosity of concentratedpolymer solutions is very high and as the concentrationincreases further starts to show some solid-like behavior.





Brookfield (Rotational) Viscometer:Measurement by sensing the torque required to rotatea spindle at constant speed while immersed in thesample fluid.

Viscosity Measurement (1)



llllllll

Scale - linked toprinter

Torsiondevice

Spindle

Brabender Cup

(rotates)

Heat-at 1.5oC per Minute

Viscosity Measurement (2):Brabender Viscoamylograph & Rapid Visco Analyzer (RVA)


Viscosity Measurement (3):Typical Brabender Viscoamylograph profile


Viscosity Measurement (3):Typical Brabender Viscoamylograph profile


Viscosity Measurement (3):Typical Rapid Visco Analysis (RVA) profile of heat treated flour (150oC, 15 min) in water.

Visc

osity

[RVA

Uni

ts,R

VU]



Key features of the viscosity curve

Pasting temperature:

Provides an indication of the minimumtemperature required to cook a givensample, can have implications for thestability of other components in aformula, and also indicate energycosts.Vi

scos

ity [R

VA U

nits

,RVU

]




Peak Viscosity:Indicates the water-holding capacity ofthe starch or mixture.

It is often correlated with final productquality, and also provides an indicationof the viscous load likely to beencountered by a mixing cooker.

Visc

osity

[RVA

Uni

ts,R

VU]





Holding Strength:Provide information on the ability of asample to withstand this heating andshear stress is an important factor formany processes.

Visc

osity

[RVA

Uni

ts,R

VU]




Breakdwon ofViscosity:The rate breakdown to a holdingstrength,depends on the temperatureand degree of mixing, or shear stress,applied to the mixture, and the natureof the material itself.

Visc

osity

[RVA

Uni

ts,R

VU]




Final Viscosity:The most commonly used parameterto define a particular sample’s quality,as it indicates the ability of the materialto form a viscous paste or gel aftercooking and cooling.

Visc

osity

[RVA

Uni

ts,R

VU]




Setback of Viscosity:- Re-association between starchmolecules during cooling.- It involves retrogradation, or re-ordering, of the starch molecules, andhas been correlated with texture ofvarious products.

Visc

osity

[RVA

Uni

ts,R

VU]


Viscosity Measurement (4):RVA Applications : https://www.researchgate.net/figure/Viscosity-measured-in-Rapid-Visco-Analyser-units-RVU-for-blends-of-sound-and-sprouted_fig2_255604907

Crosbie, G.B. , Ross, A. S.,Moro,T., and Chiu, P. C. 1999.Starch and Protein QualityRequirements of Japanese AlkalineNoodles (Ramen).Cereal Chem. 76(3):328–334.

Viscosity measured in Rapid-Visco Analyser units (RVU) for blends of sound and sprouted whole meal flour.Eradu tested in water (A) and 1 mM AgNO3 (B). Kulin tested in water (C) and 1 mM AgNO3 (D).Falling number values were 177–472 sec for Eradu and 161–427 sec for Kulin


Viscosity Measurement (5):Bostwick Consistometer

• A simple, dependable instrument which determinessample consistency by measuring the distancewhich a sample of material flows under its ownweight

• The unit is constructed of stainless steel andis equipped with two leveling screws and alevel.

• The gate is spring operated and held by apositive release mechanism, permittinginstantaneous flow of sample. The trough isgraduated in 0.5cm divisions.

• Used extensively in the food industry for jams, jellies,tomato paste, ketchup, condensed soup and otherhighly viscous products.



30 sec reading

Viscosity Measurement (6):Bostwick Consistometer


Texture Analyzers- Solid Foods


Texture Analyzer:Solid Foods– Relationship of STRESS & STRAIN

Sifat Reologi Bahan - 1



Sifat Reologi Bahan - 2


• A variety of lab instruments exist thatcarefully control distance andmeasure force while probing a foodsample

• These instruments can be fitted witha wide variety of probes and fixtures



• LFRA Texture AnalyzerTexture Analyzer:



• Stable Micro Systems, TA XT2, TA XHDTexture Analyzer:


• Stable Micro Systems, TA XT2, TA XHD -- probesTexture Analyzer:


• InstronTexture Analyzer:


Typically, these devicesmeasure force as the probe islowered or raised

Texture Analyzer:


• A flat probe is lowered on the sample• Sample is contained within area of

probe• Measure maximum force, force to break

or work (sometimes distance) to breakused as measure of firmness orhardness

• Examples: carrot cylinders, cake, gels,rice, bread rolls

Texture Analyzer:- Compression test





Force

Distance

Maximum force at compression, or break point



Force

Distance

Work is areaunder the curve

W Fdx



W = Fdx0

3

∫• Compressive force shown directly vs time (speed 4 mm/s)• The work done on the sample up to 3mm is :





• Smaller cylinder is pushed into sample• Maximum force to reach specified distance;

force at yield point; mean plateau force• Apples, cookies, bread, caramel, cherries,

fish, fondant, gels, ice cream, peppers,surimi

• Probe may be cylinder, cone, or ball

Texture Analyzers• Penetration test penetrometer


Types of probes used for penetration test




Cone Penetrometer Probes







• Measure force required to snap a rigidfood sample

• Knife edge lowered to a thin food across abending platform

• Bending force generated until materialsnaps

• Biscuits, cookies, carrot,chewing gum,crackers, dry lasagne, pretzels

• Used with snack chips, thin crisp items

Texture Analyzers• Snapping test







• Force applied to sample until it flowsthrough slots, holes, or annular spaces

• Maximum force to extrude product ismeasure of firmness or tenderness

• Viscous materials including some gels,fats, peas, catsup

Texture Analyzers• Extrussion test


Mat erial compressesMat erial begins t o beext ruded t hroughannular ring

Texture Analyzers• Extrussion test – Back extrusion

- FMC Pea Tenderometer


FORCE

DISTANCE

A

B

C

D




FORCE

DISTANCE

A

B

C

D

• A-B peas deformed and packed moretightly

• B peas packed solid; liquid begins to beexpressed and fill spaces

• B-C force increases as juice is expressed• C-D peas rupture and flow through annulus




Back extrusionPeas,mayonnaise,rice pudding, syrup,yoghurt


-


Texture Analyzers:• Extrusion Test – Forward Estrusion:

force material through a hole



Forward extrusion:Baking fats,ketchup

Texture Analyzers:• Extrusion Test – Forward Estrusion:

force material through a hole


TEXTUREPROFILEANALYSIS(TPA)


• Attempt to correlate instrumentalmeasurements with sensory descriptions

• First developed by Friedman; Szczesniak(1963) at the General Foods Corporation:General Foods Texturometer

• Modified by Malcolm Bourne for the TPA(~ Instron)

TEXTURE PROFILE ANALYSIS


TEXTURE PROFILE ANALYSIS• Ilustration : Bite-sized food compressed 2

times to simulate chewing• ~1 cm3 (bite size pieces) compressed

(and decompressed) 2 times

• Develop plot of force vs. time



times to simulate chewing















Down Up Down Up

Force

Time


times to simulate chewing• plot of force vs. time


TEXTURE PROFILE ANALYSIS- Definition

- Fractuability: force required to produce firstsignificant break in the curve on the first bite.

- Popular terms: crumbly, crunchy, brittle

Fractuability

Down Up Down Up

Force

Time



- Hardness: force exhibited in first bite atmaximum compression

- Popular terms: soft, firm, hard

Fractuability

Down Up Down Up

Force

Time

Hardness



A1


- Cohesiveness: Ratio of the positive force areasunder first and second compressions (A2/A1); Usuallyuse only areas under the compression part of curve(not decompression) see Figure.

A2

Fractuability

Down Up Down Up

Force

Time

Hardness



- Adhesivenes: work to pull the plunger awayfrom the sample after the first compression (A3)

- Popular terms: sticky, tacky, gooey

A3

A1 A2

Fractuability

Down Up Down Up

Force

Time

Hardness



- Springiness: Distance over which the material recoversits height between the end of the first bite and the startof the second bite (L2)

- Popular terms: plastic, elastic

A3

A1 A2

Fractuability

Down Up Down Up

Force

Time

Hardness

L2



- Springiness: Distance over which the material recoversits height between the end of the first bite and the startof the second bite (L2)

- Springiness sometimes defined as by a ratio L2/L1

A3

A1 A2

Fractuability

Down Up Down Up

Force

Time

Hardness

L2L1



- Stringiness: the distance that the product is extended duringdecompression before separating from the probe.

A3

A1 A2

Fractuability

Down Up Down Up

Force

Time

Hardness

L2L1

Stringiness



- Resilience: A measurement of how the sample recoversfrom deformation. (A5/A1)

- Ratio of the first UP ( decompression) stroke to the firstDOWN (compression) stroke

A3

A1 A2

Fractuability

Down Up Down Up

Force

Time

Hardness

L2L1

Stringiness

A5




- Gumminess: hardness X cohesivenessPopular terms: short, mealy, pasty, gummy

- Chewiness: gumminess X springinessNote: Gumminess and chewiness are notreported for the same food!

A3

A1 A2

Fractuability

Down Up Down Up

Force

Time

Hardness

L2L1

Stringiness

A5


TEXTURE PROFILE ANALYSIS

More… read :

1. Bourne, M.C. (2002). Food Texture andViscosity: Concept and Measurement 2nd Ed.Academic Press. New York.

2. An Overview of Texture Profile Analysis (TPA)(http://texturetechnologies.com/texture-profile-analysis/texture-profile-analysis.php)

3. Texture Profile Analysis Explained & Annotated(http://128.121.92.221/texture_profile_analysis.html)

____________________________


TERIMAKASIH

phariyadi.staff.ipb.ac.id

purwiyatno_hariyadi

@phariyadi

analysis of what is texture? food...

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