www.anton

paar.com
Rheology
of food materials
2
Food products: life cycle
Food
products
Rheological characterization
Formulation

Composition,
additives and
stabilizers
Viscosity and flow behavior of
formulation
Production
Flow behavior, viscosity, elasticity
Storage
Sedimentation stability, thermal
stability
Application (usage)
Flow behavior under shear
conditions,
Thixotropy
3
Rheology road
Rheology road and measuring system
4

Measuring systems for rotational and oscillatory rheometers

Flow and viscosity curves in a wide shear rate range
Examples: Water; Polymer solutions (polysaccharide); Emulsions; Binder solutions

Special measuring systems: measuring with the ball measuring system
Examples: Marmalade, Bolognese sauce with meat chunks

Yield point in flow curves (via rotational tests)
Examples: Creams; Ketchups

Yield point as the limiting value of the linear

elastic deformation range (via rotational tests)
Example: Ketchup

Structure at rest as G’ value (via oscillatory tests: amplitude and frequency sweeps)
Examples: 1) Butter; 2) Starch gels; 3) Pudding; 4) Milk drinks; 5) Emulsions

Structure regeneration of coatings, leveling, sagging behavior and layer thickness

Step tests (oscillatory and rotational tests)
Example: Ketchup

Temperature

dependent behavior during heating, softening, melting, cooling, solidification,
crystallization (using rotational and oscillatory tests)
Examples: Chocolate; Ice creams; Spreading cheese and melting cheese

Gel formation (using time

dependent and temperature

dependent rotational and oscillatory tests)
Examples: Corn starch; Gelatin
Overview
5
Typical shear rates
Process
Shear rate range [s

1
]
Examples of application
Sedimentation
(fine particles in
a suspension)
10

6
to 10

4
Salad dressing, fruit juice
Leveling

due to surface tension
10

2
to 10

1
Coatings, printing inks,
lacquers, chocolate
Dip coating
1 to 10
0
Chewing
,
swallowing
Pouring from a bottle
10 to 100
Cheese, yogurt, chocolate
Transport in tubes, pipe flow,
pumping, filling into
containers
1 to 10
4
Blood, crude oils, paints, juices
Mixing
,
stirring
10 to 10
4
Emulsion,
plastisol
, polymer
blends
Brushing
,
painting
,
spraying
,
blade coating
100 to 10
4
Brush coating, tooth paste,
butter
6
Materials
Shear viscosity
Gases / air
0.01 to 0.02 / 0.018
mPas
Water at 20
°
C
(at 0 / 40 / 60 / 80 / 100
°
C)
1.0
mPas
(1.8 / 0.65 / 0.47 / 0.35 / 0.28
mPas
)
Milk,
coffee
creams
2 to 10 mPas
Olive oil
approx. 100
mPas
Glycerin
1480
mPas
Polymer melts (T=+100 to +200
°
C
and at shear rates of 10 to 1000 1/s)
10 to 10 000 Pas
Polymer melts (zero

shear viscosity)
1
kPas
to 1MPas
Bitumen (T = +80 / +60 / +40 /
+20 / +0
°
C)
200 Pas / 1
kPas
/ 20
kPas
/
0.5
MPas
/ 1
MPas
Viscosity values
7
Typically used measuring systems
Cone

plate and plate

plate systems
Use
sandblasted
or
profiled
measuring
systems
for
oily
and
fatty
substances
!
Viscoelastic, high
viscous
, caution to particles and
structures sizes
Paste like, sticky and almost not flowing
Viscoelastic, medium
viscosity
(f
ree
flowing and
significantly above 100
mPas
(1000mPas)
(larger
particles
or
super
structures
)
Low
viscosity
CP75

0,5
CP50

1
PP50
CP25

1, CP25

2,
CP25

2
PP25
Gel

like
samples
G
‘ > G‘‘
and
temperature
tests
Profiled geometries for
mozarrella
type of cheeses,
sandblasted for cream cheese
Viscoelastic, medium
viscosity
(f
ree
flowing and
significantly above 100
mPas
(1000mPas)
Flowing liquid but larger super

structures (CP50

2)
8
Cone with truncation:
CPxx
: Cone & Plate
Cone truncation
+ Shear rate and shear strain constant
+ Easy to clean

Measurement of friction if particles are below the tip of the cone
Standards: ISO 3219, DIN53019, DIN53018
Crash!!
Name
Cone
Truncation

[µm]
CP25

1
50
CP25

2
105
CP25

3
170
CP35

3
240
CP50

0.5
50
CP50

1
100
CP50

2
210
CP50

3
345
CP60

0.5
60
CP60

1
120
CP60

2
250
CP75

1
150
CP75

2
315
cone truncation
=
measuring gap
9
Double Cone BI

C60

1
°
Applications: Food, Cosmetics,
Pharma
modular
Bi

cone
for inset

Peltier
precise determination of melting and crystallization temperature
homogenous heating and cooling
low temperature measurements without condensation (inert, dry)
no evaporation of water or solvents
Peltier basis

c
ontrol by conduction
Peltier

hood
heating & cooling
by convection
and radiation
N
2
10
PTD
–
Peltier Temperature Device
Excellent temperature control from the bottom to the top
unique
combination of
radiation
,
convection
(frost protection) &
conductive heating & cooling
homogenous
heating and cooling
low
temperature measurement without having
condensation (inert, dry)
frost formation
Peltier

Hood
Heating
/
Cooling
by
Convection
and
Radiation
Peltier Basis
Temp.

Control
by
Conduction
optional
evaporation
blocker
11
Sealing the Gap: PP & CP
Applications: Food, cosmetics, coatings
2

guard ring
oil
(10 mPas Si

Oil
)
evaporation of solvent / water ?
skin formation ?
12
Sealing the Gap: PP & CP
Applications: Food, cosmetics, coatings
evaporation of solvent / water ?
skin formation ?
1a

solvent trap
sample
solvent
13
Typically used measuring systems
Concentric cylinders systems
Standards: ISO 3219, DIN53019, DIN53018
Easy to prevent sample from drying

out (oil film on top of sample)
No trimming
Good solution for all kind of liquids in rotational mode
CC: not recommended for oscillation; DG: also recommended for oscillation
CC: Helical groove if phase separation or vertical profiling to prevent slippage
Above 10mPas and below 100mPas with super

structures
DG27 (same dimensions like CC27), gap size = 1mm
Above 1000mPas (100mPas)
CC27
Above 10mPas and below 1000mPas
CC39
Below 10mPas und homogenous, small structure
DG26.7, gap size = 0.4mm
14
0.1
1
10
mPas
0.01
0.1
1
10
1000
mPa
1
10
100
s

1
DG 42
(double gap MS)
T = +20
°
C
Double

gap
measuring
systems
are
special
systems
designed
for
low

viscosity
liquids
.
constant viscosity
water
lg
lg
t
lg
Flow
Behavior
:
ideally
viscous
behavior
15
A special measuring system
for:
E.g. natural yoghurt
Natural Food Products
Measure natural product without destroying the initial structure
by cutting into the sample structure
Advantages:
allows
measurement of
brittle, natural materials
excellent penetration characteristics
dimensions similar to standard CC27
alternative: combination with flexible cup holder

>
ST22

4V

40 measuring system
aluminum cup
or stainless steel cup
16
Coarse disperse materials
Building materials
Slurries
Food (Yoghurt)
Special Geometries
CC
with
Surface
Treatment
or
Vanes
,
Stirrers
, Propellers
Better grip
No slip
More Stirrers on request:

User defined

Brookfield Spindels

Krebs Stormer
Spindels

...
17
All these stirrers are
relative
measuring systems
Special
Geometries (Relative
Values)
Helix 1
Helix 2
Stirrer for
Building Materials
Starch
Stirrer
Blade
Anchor
Ball Measuring System
18
Rheometry with special Geometries
Ball Measuring System (BMS)
for dispersions containing
coarse

grained particles
(showing a diameter up to 10mm)
Example: Marmalade
containing fruit pieces
19
Rheometry
with
special
Geometries
Ball
Measuring
System (BMS)
1
10
100
1,000
Pa
1
10
100
1,000
Pa·s
0.1
1
10
100
1/s
Shear Rate
.
Flow and Viscosity Curves of Jams at 23 °C
Measured with the Ball Measuring System
Anton Paar GmbH
blueberry
KMS3 /Q1; d=0 mm
Shear Stress
Viscosity
lemon
KMS3 /Q1; d=0 mm
Shear Stress
Viscosity
Flow and Viscosity Curves of two
Marmalade
Preparations
20
Rheometry
with
special
Geometries
Ball
Measuring
System (BMS)
Flow and Viscosity Curves of a
Sauce Bolognese
10
0
10
1
10
2
10
3
Pa
t
10
0
10
1
10
2
10
3
10
4
Pa∙s
10

4
10

3
10

2
10

1
10
0
10
1
10
2
1/s
Shear rate
.
Copyright (C) 1999 Physica Meßtechnik GmbH
meat sauce
KMS

1M
t
shear stress
viscosity
meat sauce (new sample)
KMS

1M
t
shear stress
viscosity
Spaghetti Sauce
containing meat pieces
(testing reproducibility)
21
Further measuring systems/ temperature
control systems
Starch (pressure) measuring cell
Tribology
cell
Penetration measurements
Interfacial rheology (IRS)
Sentmanat
extensional rheology(SER)
Flexible
Toolholder
Rheo

Microscopy
22
Flow
Behavior
Rheo

Microscopy
Size and shape
of the droplets
are depending
on shear rate
and
“shear history”.
water / oil emulsion
dispersions
lg
23
Shear

Thinning flow
B
ehavior
Suspension 1:
Orientation of particles
(needle shaped)
Suspension 2:
Agglomerated particles
Break

up of agglomerates
Emulsion:
Deformation and break

up of
droplets
high
viscosity
low viscosity
rest
high shear rates
24
Shear

Thickening flow
B
ehavior
At low shear load:
The rod inclines slowly.
Low viscosity
At high shear load:
Solidification of the liquid
due to shear thickening.
High viscosity
25
Suspensions
shear

thickening
of suspensions at

high solid concentrations

high shear loads
Flow
Behavior
Shear

thickening
Behavior
1
f
... volume fraction of solid particles
dispersions
26
Flow Curves on a
linear
scale
Yield
Point
as
a
limiting
value
of
the
shear
stress
1
without
a yield point
2
having
a yield point
t
y
2
1
t
y
Flow
Behavior
Yield
Point
Break
of
the
structure

at

rest
.
Super

structure
by
a
chemical

physical
network
via
interactive
forces
.
t
The applied force is
higher than the
structural force
Low stress
…no movement
High stress
…sample starts moving
t
1
t
2
Examples
: Pastes, concentrated dispersions, suspensions, ketchups, mayonnaises, chocolate
melts, butter, gels
27
0
500
1000
1500
2000
2500
Pa
t
0
200
400
600
1000
s

1
shear rate
Ketchup
t
shear stress
Yield point can hardly be
read

off
Flow curve
showing a
yield point
(on a
linear scale
)
Flow behavior: yield point
28
10
100
1000
10
4
Pa
1
10
100
1000
s

1
Ketchup
Flowcurve
showing
a
Yield
Point
(on a
logarithmic
scale
)
yield point
t
y
= 48 Pa
food
Flow
Behavior
Yield
Point,
comparison
lin
/ log
diagrams
(2)
lg
t
lg
29
Flow curves on a
logarithmic scale
t
y
Flow behavior: yield point
Yield point analysis
in the low

shear range,
e.g.
read off
at = 0.01 s

1
t
y
Yield point analysis
in the low

shear range,
e.g.
read off
on the
t

=
慸楳
30
Mathematical curve fitting
for flow curves on a
linear scale
(approximation, "regression")
other often used models:

Casson
blood,
food

Herschel /
Bulkley
materials with a yield
stress and shear thinning or shear
thickening behavior
Flow behavior: yield point
Bingham
:
flow curve of a
material with a yield stress
and a constant viscosity
(
food
or cosmetics
)
t
B

“
y
ield point
acc. to
Bingham“
B

“Bingham viscosity“
Windhab
:
chocolate
and
other cocoa products
t
0

y
ield point
t
1

linear
y
ield point

“high

shear
viscosity“
examples:
models
according to
31
0
200
400
600
800
1,200
Pa
t
0
50
100
1/s
Cream 1
t
Shear Stress
Cream 2
t
Shear Stress
Cream 1 Herschel Bul kl ey
tau0 = 705.01 Pa; b = 11.503; p = 0.84742
t
Shear Stress
Cream 2 Herschel Bul kl ey
tau0 = 31.224 Pa; b = 4.7648; p = 0.94538
t
Shear Stress
Analysis
using
Approximation
Functions
for
Flow
Curves
here
:
according
to
Casson
(OICC 1973),
and
Windhab
(IOCCC 2001 / ICA)
0
50
100
150
200
250
300
Pa
0
10
20
30
40
50
1/s
Scherrate
.
Anton Paar GmbH
Zartbitter 2
Schubspannung
Weiße 1
;
A4...A4
Schubspannung
Vollmilch
;
A4...A4
Schubspannung
Chocolate
Melts
(T = +40
°
C)
Bitter
White
Whole Milk
Analysis
Casson
Windhab
t
0
(
Pa
)
t
0
(
Pa
)
Bitter
15
18
White
19
25
Whole
Milk
21
23
shear
rate
food
Summary
:
Yield
Points
are
not
material
constants
,
since
they
are
depending
on
the
measuring
method
and
on
the
analysis
method
.
t
Flow
Behavior
Yield
Point
32
Viscoelastic
Behavior
Yield
Point (
using
a
/
t

Diagram
)
Testing
with
controlled
shear
stress
Yield
point
as
the
limiting
value
of
the
shear
stress
:
The sample
starts
to
flow
not
before
the
external
forces
are
exceeding
the
network

of

forces
of
the
internal
structure
.
Below
the
yield
point
there
is
elastic
deformation
.
yield
point
t
y
using
the
best
fit
straight
line
(
“
tangent
“
)
in
the
linear

elastic
deformation
range
yield
point
t
y
using
the
„
tangent
crossover
“
method
lg
t
lg
lg
lg
t
33
10

2
10
0
10
2
10
4
10
6
%
lg
0.1
1
10
100
1000
Pa
shear
stress
lg
t
without binder
yield point 13.5 Pa
with binder
yield point 114 Pa
Comparison
of
two
Ketchups
deformation
food
Viscoelastic
Behavior
Yield
Point (
using
a
/
t

Diagram
)
34
Introduction
Viscoelastic
Behavior
liquid

like
structure
„at the gel
point“
gel

like
structure
G
''
>> G
'
G
''
> G
'
G'' = G'
G' > G''
G
'
>> G
''
tan
d
㸾=1
=
=
tan
d
㸠1
=
tan
d
=
1
tan
d
㰠1
=
瑡t
d
㰼=1
=
0
with
tan
d
=
G'' / G'
viscous
viscoelastic
elastic
35
Application
Shear
Modulus
Material
Stiffness
and
Shear
Moduli
Example
:
different
types
of
cheese
cheese
type
example
shear modulus
(around)
1
cream
Philadelphia
1
kPa
2 soft
French
Camembert
10
kPa
3 semi

hard
Holland Gouda
(young)
0.1
MPa
4 hard
Swiss
Emmentaler
0.5
MPa
5 extra hard
Italian
Parmigiano
1
MPa
5
1
2
4
36
100
1000
10,000
Pa
1
0.1
1
10
100
%
Gel Strength
, Dependence on the Binder

Concentration
15 w

%
10 w

%
7.5 w

%
5% w

%
0.1
10
Viscoelastic
Behavior
Amplitude
Sweeps
ω = 10 rad/s
T = +23
°
C
loss factor
tan
d
= G‘‘ / G‘
Starch Gel
(in water)
Summary:
Gel strength
is dependent
on the binder
concentration
First check in the LVE range:
tan
d
< 1
for all samples
( = gel structure) ?
Yes !
food
lg tan
d
lg
G'
strain lg
37
0.01
0.1
1
10
MPa
0.01
0.1
1
10
%
ω = 10 rad/s
Temperature
Dependence
of
Butter
Viscoelastic
Behavior
Amplitude
Sweeps
Summary:
cold butter shows
brittle break
,
hence
poor spreadability
T = +10
°
C
T = +23
°
C
food
lg
G'
lg G''
strain lg
38
10
2
10
3
10
4
10
5
Pa
G'
G''
10
0
10
1
10
2
10
3
Pa
0,001
0,01
0,1
1
10
100
%
Deformation
am03014
Margarine css
CP 502; d=0,05 mm
G'
Speichermodul
G''
Verlustmodul
Schubspannung
10
2
10
3
10
4
10
5
Pa
G'
G''
10
1
10
0
10
1
10
3
Pa
0,001
0,01
0,1
1
10
100
%
Deformation
am03014
Margarine CSD
CP 502; d=0,05 mm
G'
Speichermodul
G''
Verlustmodul
Schubspannung
Amplitude
Sweep
/CSD /CSS
Margarine
as
semi

solid material
with
flow
point
CSD
CSS
39
Application
Sedimentation, Long

term
Storage
Stability
in the beginning
Stability of Dispersions
Example:
Salad Dressings
after 15min
Behavior in the low

shear range or at rest, respectively
dispersions
40
Frequency
Sweep
Stability
of
suspensions
t = 1 /
omega
Time
dependent
structural
strength
G’
decreasing

Long
term
behavior
=
Fluid

like

Strength
of
the
structure
G’
decreases

Good
flow
characteristics

Low
stability
G’
constant
,
light
decreasing

Long time
structural
strength
G‘

Bad
flow
characteristics

High
stability
1
1
2
w
=1/
Time
G‘‘
2
G‘
1
2
41
Milk:
Geometry
DG26.7*
Pure milk
Chocolate Milk
Plus
Chocolate Milk
Budget
Ca
enriched
Mill
Mechanical
storage
stability
Amplitude
Sweep
Sedimentation

Stability
42
Amplitude
Sweep
Structural
strength
G
´
as
function
of
stress
TAU
LVE
=
Yield
stress =
External
force
to
overcome
the
structure
at
rest
Shear
stress
t
=
*)
Strain

Test
,
plottet
as
function
of
strain
10

4
10

3
10

2
10

1
Pa
G'
0,0001
0,001
0,01
0,1
Pa
Pure Milk (
no
G‘ )
t
LVE
t
LVE
t
LVE
CA Milk
CHOC
budget
CHOC plus
43
Measurement
of
structural
strength
at
rest
or
mechanical
stability
of
milk
Frequency
Sweep
Sedimentation
Stability
10

4
10

3
10

2
10

1
10
0
Pa
G'
0,1
1
10
100
1/s
w
Pure milk
DG 26.7
G'
Choc milk,
plus
DG 26.7
G'
Choc
milk,
Std.
DG 26.7
G'
CA

Milk
DG 26.7
G'
44
Spread
cheese
Temperature
behavior
Flow
point
=
Spreadability
as
crossover
point
at
G‘ = G“
Spread
cheese
5
°
C
G'
G''
Spread
cheese
20
°
C
G'
G''
Spread
cheese
36
°
C
G'
G''
10
3
10
4
10
5
Pa
G'
G''
10
2
10
3
10
4
Pa
t
=
5
°
C
20
°
C
36
°
C
Amplitude
Sweep
Representation
as
function
of
stress
to
determine
the
flow
points
45
Penetration measurements
Soft cheese
Presetting
0.3N
contact
pressure
Temperature
60
°
C
Temperature
of
cheese
before
test
ca
. 25
°
C
0
2
4
6
10
mm
d
0
10
20
30
40
60
°C
T
0
2
4
6
8
10
12
14
min
Zeit
t
Penetration Test
Anton Paar GmbH
Start
End
Depth
Time
46
1
0,5
0
0,5
1
2
N
F
N
2.000
1.500
1.000
500
0
500
1.000
2.000
µm/s
v
0
5
10
15
20
25
s
Zeit
t
Penetration
measurement
Margarine
Presetting
: Penetration
velocity
down/
up
= 2000µm/s
Alternatively
: Normal
force
controlled
testing
stop
up
down
Time
47
Flow
Behavior
Temperature

dependent
Behavior
softening
and
melting
,
or
solidification
and
crystallization
preset
:
constant
shear
conditions
(
shear
rate
or
shear
stress)
result
:
viscosity
/
temperature
curve
with
steadily
decreasing
or
increasing
viscosity
values
,
respectively
gel
formation
and
curing
preset
:
constant
shear
conditions
(
shear
rate
or
shear
stress)
result
:
viscosity
/
temperature
curve
showing
a
viscosity
minimum
T
T
min
48
0
2
4
6
8
10
Pas
20
25
30
35
40
°
C
temperature
T
Chocolate
Melt
Flow
Behavior
Temperature

dependent
Behavior
Cooling
process
:
Crystallization
Temperature
of
Cocoa
Butter
food
crystallization
49
Starch gelling
Electrical heated cell
Watercooling
Fast heating and cooling
rate
Stirrer acts against
sedimentation of particles
50
melting
or
crystallization
process
preset
:
constant
shear
conditions
(
amplitude
and
frequency
)
(
with
an
amplitude
in
the
LVE

range
,
and
mostly
with
ω = 10 rad/s)
T
k
... crystallization temperature
result
:
steep decrease or increase, resp.,
in a
narrow
temperature range
Viscoelastic
Behavior
Temperature

dependent
Behavior
51
preset:
= 0
.
02 %
ω = 10 rad/s
T = T(t)
Viscoelastic
Behavior
Temperature

dependent
Behavior
food
melting
10
2
10
3
10
4
10
5
10
6
10
8
Pa

20

15

10

5
0
5
10
°
C
temperature
T
Advantages of icecream 2:
1) better separable at
–
20
°
C
2) less cold

feel when melting
3) creamier feel at molten state
lg G'
lg G''
1
2
Comparison of two Ice Creams
1 Old Freezer
2 New Freezer
52
10
1
10
0
10
1
10
2
Pa
G'
G''
30
35
40
45
50
55
60
65
70
75
°C
T
0
20
40
60
80
100
min
Time
t
Anton Paar GmbH
Vegetable Fat 10%
G'
Storage Modulus
G''
Loss Modulus
T
Temperature
=1 %
w
=10 1/s
Crystallization of a Vegetable Fat
Rheo

Microscopy
53
Different Behavior of two Ketchup Samples
fast
structure recovery
slow
structure recovery
Viscoelastic
Behavior
Time

dependent
Structure
Recovery
for coatings:
high wet

layer thickness,
good film stability
for coatings:
small wet

layer thickness,
good levelling
54
Viscoelastic
Behavior
Time

dependent
Structure
Recovery
preset:
1 low

shear conditions
(strain in the LVE

range, oscillation)
2 high

shear conditions (rotation)
3 low

shear conditions
(strain in the LVE

range, oscillation)
measuring result:
1 state of rest
2 structure decomposition
3 structure regeneration
Step test with 3 intervals, as oscillation / rotation / oscillation
(measuring „thixotropic behavior“)
2
nd
test interval:
liquid, at high shear rates
1
st
& 3
rd
test interval:
G‘ > G‘‘ („gel

like structure“ at rest)
www.anton

paar.com
10
100
1000
Pa
G'
G''
0.4
0.6
0.8
1.0
Pas
=
0
50
100
150
200
250
s
time
t
Ketchup
G'
G''
1
=
3
= 0.3 %
ω = 10 rad/s
=
〠s

1
T = +23
°
C
Step test: oscillation / rotation / oscillation
Viscoelastic behavior: time

dependent
structure recovery
56
Interfacial
Rheology System (IRS)
MCR Rheometer +
Interfacial
Rheology System (IRS)
H
1
= 22,5
mm
H
2
= 45
mm
R = 40
mm
R
2
= 34,14
mm
2
= 10
°
P. Erni et. al.
J.Rev.Sci.Instr.
,
74(11)
, 4916

4924 (2003)
57
IRS: Film
Formation
of
a Coffee Sample
at
different
Concentrations
0.1% strain, frequency 1Hz
0.05g, 0.15g, and 0.3g coffee powder / 114ml double distilled water
10
6
10
5
10
4
10
3
10
2
10
0
Pa·m
G
i
'
G
i
''
0
200
400
600
800
min
Time
t
G
i
´
= 3*10

5
Pa
*m
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