credit seminar 1

Major advisorDr. B. B. NayakPrincipal Scientist, POST HARVEST TECHNOLOGY, CIFE, MUMABI

Presented byNaresh Kumar MehtaE-mail-nareshfishco@gmail.com(PHT-PA01-04)Ph.D. (Batch: 2011-14), POST HARVEST TECHNOLOGY, CIFE MUMBAI

Texture Profile Analysis (TPA), Rheology and

Tribology : Application in FISH PRODUCT

DEVELOPEMENT

Credit seminar (PHT-691)

Overview

• The food structure design rules for many existing products

have been well established , although not necessarily

understood.

• Current drive to produce healthy consumer acceptable foods

• Both subtle and large scale alterations to formulations can

result in significant changes in texture and mouth feel and

texture related quantities such as rheology

• India fish export comprises more or less fresh or frozen fish

but not processed fishery products.

Instrumental perspective

• Food technologists have sought for a long time to

instrumentally measure “texture,” despite the caveat that

it is a multi-modal sensory percept.

There are three key approaches:

(i) Imitative techniques (e.g., using so-called texture

analysers)

(ii) Empirical methods (puncture & extrusion test) that seek

to align any sort of measurement to a sensory perception and

(iii) Fundamental mechanical properties of the food such as

rheology and its underlying structure.

TA ,Rheomter & what next ??

• A imitative test to provide standardised values of food texture is

the so-called “Texture Profile Analysis” .

• The technique involves measuring the mechanical response

during a double compression, which attempts to mimic first and

second bite of a food sample and various parts of the

measurement are referred to as hardness, elasticity, adhesiveness,

cohesiveness, brittleness, chewiness, and gumminess.

Down Up Down Up

Forc

e

Time

Fracturability

First bite Second bite

Down Up Down Up

Forc

e

Time

FracturabilityHardness

A1A2

A2

A1

Cohesiveness =

Down Up Down Up

Forc

e

Time

FracturabilityHardness

A1A2

A3

Adhesiveness = A3

Down Up Down Up

Forc

e

Time

A1A2

A3

Springiness

Down Up Down UpF

orc

e

Time

A1A2

A3

L2

L1

Down Up Down UpF

orc

e

Time

A1A2

A3

Stringiness

Down Up Down UpF

orc

e

Time

A1A2

A5

Resilience = A5

A1

Shortcomings

• Correlations on which the sensory tests have been made are not

particularly strong or linear hence substantial potential for abuse

as the methods are often used blindly with measurements

incorrectly reported as definitive measures of “texture” .

• Like presence of pin bones, scales or any other hard particles may

completely give false measurements

• Empirical approaches (puncture & extrusion test) is quicker

and simpler than fundamental testing but having good

correlation with textural quality.

• For solid materials, the modulus and force or stress to fracture

are discussed in terms of ‘first bite’ and good correlations with

sensory at this stage are generally found.

• Some instruments are designed for a specific purpose and give

only instrument specific parameters. A gel rheology test using

this type of instrument is called an empirical test, which is of

value if a correlation with a property of interest is found.

• A fundamental test has the advantage over an empirical test in

determining true (i.e., material-characteristic and instrument-

independent) physical properties.

• Results cannot be compare with other testing methods

The puncture test

• It consists of measuring the force required

to push a plunger into a food sample, which

is thus subjected to a combination of

compression and shearing in proportion to

the area of the cross-section of the plunger.

• Different shapes of plunger have been used

(conical, cylindrical, wedge-shaped).

• The plunger penetrates either to a constant

depth or to the point of rupture. The applied

force can increase linearly or at a constant

rate.

• The parameters normally measured are

force at the point of rupture, slope and

energy of the force±deformation curve or

the depth of penetration over a constant

time.

• This method has been used to assess the changes occurring intexture during storage in ice that reflect variations in textureassociated with the onset and resolution of rigor mortis, andhas shown good correlations with sensory analysis.

• It has also been successfully used when analysing texture offish gels.

• The term rheology was coined by Eugene C. Bingham, a

professor at Lafayette College, USA, in 1920, from a

suggestion by a colleague, Markus Reiner.

• Rheology is used to develop constitutive relationships between

stress and strain rate, and foods are generally more complex

than most materials because they are also strongly dependent

on time scales of the deformation process (thixotropy,

elasticity, etc.) as well as shear and thermal history

(processing).

• While there is much research that seeks to link the triangle of

rheology– structure–processing.

• In many cases food consist of mixtures of solids and fluid.

• As rheology concerns the flow and deformation of substances and

especially their behaviour in the transient range between solids and

fluids, it is a very useful tool.

• Rheological measurements are used to physically characterize raw

materials prior to processing, intermediate products during

manufacturing, and the final food products.

• Newtonian fluid - The viscosity of such fluids will not change as the shear rate is varied. eg,.Water and thin motor oils

• Non-Newtonian fluid - The viscosity of such fluids will change as the shear rate is varied.

The most common types of non-Newtonian fluids you may encounter include:

• Pseudoplastic - This type of fluid will display a decreasing viscosity with an increasing shear rate.

• Probably the most common of the non-Newtonian fluids, pseudo-plastics include paints, emulsions and dispersions of many types. This type of flow behaviour is sometimes called "shear-thinning."

The important terms frequently used in the rheology

• Dilatant - Increasing viscosity with an increase in shear rate

characterizes the dilatant fluid.

• Although rarer than pseudoplasticity, dilatancy is frequently

observed in fluids containing high levels of deflocculated solids

such as clay slurries, candy compounds, corn starch in water and

sand/water mixtures. Dilatancy is also referred to as "shear-

thickening" flow behaviour.

• Plastic - This type of fluid will behave as a solid under static

conditions. A certain amount of force must be applied to the fluid

before any flow is induced; this force is called the "yield value."

• Tomato ketchup is a classical example of this type of fluidplastic

fluids may display Newtonian, pseudoplastic or dilatant flow

characteristics.

(Bingham Plastic)

(Casson Plastic)

Time-dependent Fluid Behaviour

The response time of the material may be longer than response time

of the measurement system, so the viscosity will change with time.

Apparent viscosity depends not only on the rate of shear but on the

“time for which fluid has been subject to shearing”.

Thixotropic : Material structure breaks down as shearing action

continues : e.g. gelatin, cream, shortening, salad dressing.

Rheopectic : Structure build up as shearing continues (not common

in food : e.g. highly concentrated starch solution over long periods

of time Thixotropic

Rheopectic

Shear stress

Shear rate

World’s Longest Running Laboratory

Experiment – The Pitch Drop Experiment

• Pitch – derivative of tar

– @room temperature feels solid and can be shattered with a blow of a hammer

– This experiment shows that in fact at room temperature pitch is a fluid!

26Dr. Aldo Acevedo - ERC

SOPS

World’s Longest Running Laboratory Experiment – The Pitch Drop

Experiment

1927 – Prof Parnell in Univ. of Queensland Australia heated a sample of pitch and poured it into a glass funnel with a sealed stem. Three years where allowed for it to settle, after which the stem was cut.

Examine the viscosity of the pitch by the speed at which it flows from a funnel into a jar.

Only eigth drops has fallen in 80 years.

The viscosity is approximated as 100 billion times that of water.

27Dr. Aldo Acevedo - ERC

SOPS

Rheological data in fish product development. Why ?

• Determining ingredients functionality in product development

• Intermediate or final quality control

• Shelf life testing

• Evaluation of food texture by correlation to sensory data

Use of Rheometer in fishery products

• Because gels are viscoelastic materials, dynamic rheological

tests to evaluate properties of gel systems are well suited for

studying the characteristics of gels as well as gelation and

melting.

• From dynamic rheological tests in the linear viscoelastic range,

• the storage modulus, G’ and

• the loss modulus G” and

• tan δ= (G” / G’ ), the loss factor

• Prior to gelation, the material shows a typical fluid-like behaviour

(G′ < G″).

• If the size of protein aggregates becomes large enough, G′ increases

rapidly, and after some time, a cross-over point (G′ = G″) is

observed. This point and the corresponding time are often referred

to as the gel point (gelation point) and the gel time (gelation time),

respectively.

Interpretation

If a gel is formed, G′ is predominant (G′ > G″) and both G′ and G″ are

relatively independent of frequency. If ideal cross-links are formed by

permanent covalent bonding, the moduli are completely independent of

frequency.

• The lost factor (damping factor) reveals the ratio of viscous to the elastic

portion of the deformation behavior.

• If tan δ= 0° equals to elastic response

• δ= 90° or tan δ= infinite response will be viscous and

• if 0< δ < 90 ° =viscoelastic nature

• A protein gel, however, usually shows a slight frequency dependence and is

called a physical gel. When log(G′) is plotted against log(f), the slope is

slightly greater than zero and is typically less than 0.1. More elastic gels

have lower slope values, whereas more viscous gels have higher slope

values

• Tribology is the study of friction and lubrication betweeninteracting surfaces in relative motion, and the number ofinteracting surfaces in the mouth during food consumption isplentiful: teeth–teeth, tongue– palate, tongue–teeth, teeth–food, tongue–food, tongue–bolus, lips, lips–food, bolus–palate, food particles–oral surfaces, etc.

Tribology in food science

• Qin Liu, Hairong Bao , Chunrui Xi, Hanlin Miao J.R., (2014). Rheological

characterization of tuna myofibrillar protein in linear and nonlinear viscoelastic

regions. Journal of Food Engineering. 121, 58–63.

• Stokes et al. (2013). Oral processing, texture and mouthfeel: From rheology to

tribology and beyond. Current Opinion in Colloid & Interface Science. 18 349–

359 .

• Carlos Cardoso, Bernardo Ribeiro , Rogério Mendes, (2012) . Effects of dietary

fibre and microbial transglutaminase addition on the rheological and textural

properties of protein gels from different fish species. Journal of Food

Engineering 113, 520–526.

• R. Liu, S.-M. Zhao, S.-B. Xiong, B.-J. Xie, and H.-M. Liu . (2007). Studies on

Fish and Pork Paste Gelation by Dynamic Rheology and Circular Dichroism.

Journal Of Food Science. Vol. 72, Nr. 7, E399-E403.

• M. Barroso, M. Careche* and A.J. BorderõÂas, (1998) . Quality control of

frozen fish using rheological Techniques. Trends in Food Science &

Technology. 9, 223-229

References

•Thank u