Colloids in Food Industry

1. Food Colloids
Dimitra Founta
Supervisor : Prof. George Petekidis
Course: Colloidal Dispersions | Department of Materials Science and Technology
UNIVERSITY OF CRETE
21/02/2019

2. 2
1. Introduction
2. Experimental Measurements with Mayonnaise
OUTLINE
Studies in the LVE region
Studies in the NLVE region – yielding
3. Conclusions
Temperature effect ???

3. The term “colloid”—from the Greek words kolla, meaning “glue,” and eidos, meaning “like” —was first used in 1861 by
Thomas Graham
3
1.Colloids????
• Uniform mixtures that don't separate or settle out.
• Homogenous (but can appear as heterogeneous in microscopic scales)
• There are two parts to every colloid mixture: the particles and the dispersing medium.
Particles: Bigger than solutions , smaller than suspensions (~1nm-10μm)
size
1nm 10μm

4. Mixture Types
• Suspensions (>1 μm)
-Insoluble particles suspended in liquid or gas
-Separation after letting sit (exp. Sedimentation)
-Light can’t pass through completely
• Solutions(<1 nm)
-No separation of the particles and the solvent
-Light can pass through completely
4
Shake well
before useSand , Snow Ball , etc
Sugar in Water , Salt in Water, etc
Sugar-Technobyte-SEM

5. Is it colloidal?
Semipermeable membrane test
5
Tyndall effect test
Timberlake,Chemistry: An Introduction to General, Organic, and Biological
Chemistry, 7th Edition,1999,Pearson, Los Angeles Valley College
https://www.shutterstock.com/image-vector/tyndall-effect-436536265

6. 1.Colloidal Dispersions in Foods
Emulsions
Liquid
Foams
6
Dispersed Phase-in-Dispersed Medium
Gas-in-Solid
Liquid-in-Liquid
Solid-in-Liquid
Gas-in-Liquid
Solid
Foams
Sols
Liquid-in-Solid
Solid
Emulsions

7. 1.Interactions in Emulsions
7
DLVO theory
Repulsive
Attractive
r
V (r)
DLVO
Vtot = Vatt + Vrep
Secondary minimum
Binary minimum >>kBT
Energy Barrier

8. 1.Typical instabilities of Emulsions
8
Creaming Sedimentation Flocculation Coalescence
Stable
Emulsion
Too strong repulsions Too strong attractions
Phase
separation
With medium Between particles

9. 1.Emulsions Emulsifiers
9
Molecules that encourage the suspension of one immiscible phase to another
Lecithin (Soy, Egg Yolk)
B-Casein (Milk)
Poly-Glycerol Ester (PGE)
…
Hydrophilic
Lyophilic
O/W W/O
Reduction of interfacial tension
between two phases

10. • Microscopy (distribution and dimensions of droplets)
• Rheology
• Texture tests
• Odor, Color , pH
• …
1.Food Analysis Tests – Emulsion stability
10Source: Anton Paar

11. Why Rheology?
11
– Deformation or movement that occurs in a material (-)
How much did the sample move?
– Force applied to a sample (Force/unit area)
How hard did I push /twist the sample?
- A sliding deformation that occurs when there is
movement between layers in a sample
– Shear stress/shear strain rate
How resistance is it to flow?
– Stress/Strain
How “strong” is it ?
Rheology is the science of the
flow and deformation behavior of
substances. When matter flows or
is deformed there are three factors
which must be considered: the
internal structure, the external
forces which act on the substance,
and the environmental conditions,
for example temperature.
Source: Anton Paar

12. 1.Rheometer : The set up used
12
kinexus Pro +
PL20mm -
Serrated
Tools
used

13. 1.Dynamic Strain Sweep (DSS)
13
Define the linear regionG’G”(Pa)
LVE NLVE
γ (%)
𝛾 =
𝐷𝑖𝑠𝑝𝑙𝑎𝑐𝑒𝑚𝑒𝑛𝑡
𝐻𝑒𝑖𝑔ℎ𝑡

14. 1.Dynamic Frequency Sweep (DFS)
14
Time-dependent behavior of a sample in the non-destructive deformation range(LVE)G’G”(Pa)
ω (rad/s)
G″
G′
G′>G″ Solid-like
G″>G′ Liquid-like
G″ = viscous response
G′ = elastic response
Sol-Gel Transition

15. 1.Flow Curve
15
Graphical description of the flow behavior
Shearstressσ(F/A)
Shear Rate γ (s-1)
Viscosityη(Pa*s)
Shear Rate γ (s-1)
Newtonian
Pseudoplastic
Dilatant
Newtonian Fluids- Time independent

16. 2.Sample of study
Regular Mayonnaise
Oil phase 65%
16

17. 2.DSS test : System rejuvenation
17
0.01 0.1 1 10
101
102
103
104
1 rad/s
1 rad/s
10 rad/s
10 rad/s
100 rad/s
100 rad/s
G',G''(Pa)
Strain (%)
Define
the LVE

18. DFS test: Linear Regime
18
G′>G″
Solid-like
10-2
10-1
100
101
102
101
102
103
104
0.5%-Load1
0.5%-Load1
0.1%-Load2
0.1%-Load2
0.05%-Load3
0.05%-Load3
G'G"(Pa)
Frequency (rad/s)

19. 19
50 100 150 200 250 300
10-1
100
101
102
103
104
105
106
107
1
2
Viscosity(Pa*s)
Stress (Pa)
Slip effect
Regular Plate
Serrated Plate

20. 2.Flow Curves
20
10-5
10-4
10-3
10-2
10-1
100
101
102
103
10-1
100
101
102
103
104
105
106
107 Load 1
Load 2
Load 3
n(Pa*s)
𝜸 η
Shear Thinning
10-5
10-4
10-3
10-2
10-1
100
101
102
103
100
101
102
103
104 Load 1
Load 2
Load 3
stress(Pa)
Yield Stress Fluid
Apparent yield stress

21. 21
10-5
10-4
10-3
10-2
10-1
100
101
102
103
10-1
100
101
102
103
104
105
106
107
1rad/s
1rad/s
10rad/s
10rad/s
100rad/s
100rad/s
n(Pa*s)
shear strain (s-1
)
Thixotropy?
No hysteresis
Not thixotropic

22. 22
10-2
10-1
100
101
101
102
103
104
G'(Pa)G"(Pa)
Strain (%)
G' -Rejuv1
G"-Rejuv1
G' -Rejuv2
G"-Rejuv2
DSS-MAYO T=15o
C , w = 1rad/s
10-2
10-1
100
101
102
103
104
G'(Pa)G"(Pa)
Strain (%)
G'- Rejuv1
G"-Rejuv1
G'- Rejuv2
G"-Rejuv2
G'- Rejuv3
G"-Rejuv3
DSS-MAYO T=15o
C , w = 10rad/s
10-2
10-1
101
102
103
104
G'(Pa)G"(Pa)
Strain (%)
G'-Rejuv1
G"-Rejuv1
G'-Rejuv2
G"-Rejuv2
DSS-MAYO T=15o
C , w = 100rad/s
2.DSS – Reproducibility Tests
Frequency Independent Strain Sweep Tests (Minor hysteresis)

23. 23
2.DFS – Reproducibility Tests
γ = 0,5% γ = 0,1% γ = 0,05%
Solid like behavior observed in every load (in LVE)
10-2
10-1
100
101
102
100
101
102
103
104
Frequency (rad/s)
G'-Rejuv1
G"-Rejuv1
G'-Rejuv2
G"-Rejuv2
DFS-MAYO T=15o
C
10-2
10-1
100
101
102
101
102
103
104
Frequency (rad/s)
G'- Rejuv1
G"-Rejuv1
G'-Rejuv2
G"-Rejuv2
G'-Rejuv3
G"-Rejuv3
DFS-MAYO T=15o
C
10-2
10-1
100
101
102
101
102
103
104
G'(Pa)G"(Pa)
Frequency (rad/s)
G'-Rejuv1
G"-Rejuv1
G'-Rejuv2
G"-Rejuv2
DFS-MAYO T=15o
C

24. 10-2
10-1
100
101
102
103
104
Steadyviscosity(Pa*s)
Shear rate (s-1
) 24
2.Step rate tests : Steady state viscosity
𝜸 ηs
Shear Thinning
0.1 1 10 100
101
102
103
104
γ=s-1
0.01
0.03
0.05
0.1
0.2
0.3
0.5
1.0
2.0
3.0
n(Pa*S)
t(s)
MAYO - T=15o
C
.

25. Viscoelastic behavior
25
0.01 0.1 1
80
100
120
140
Stress(Pa)
Shear rate (s-1
)
n = 0,21<1
Herschel-Buckley model
σ = σο + Κ* 𝛾n
Shear thinning behavior
σο=41,86 Pa

26. 26
10-3
10-2
10-1
100
101
102
103
104
5
10
15
20
25
30
35
40
viscosity(Pa*s)
shear strain (s-1
)
Τ (οC)
2.Temperature effect on viscosity

27. 3.Conclusions • Non-Newtonian fluid
• Yield Stress Fluid – Thixotropic X
• Solid-like behavior
• Shear thinning is observed
• No strong effect of Temperature
27
Mayonnaise Characterization

28. Thank You!
28