Major advisorDr. B. B. NayakPrincipal Scientist, POST HARVEST TECHNOLOGY, CIFE, MUMABI
Presented byNaresh Kumar [email protected](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