Structuring Foods with
Polysaccharides
John Mitchell
[email protected]
Countries with most Carbohydrate Polymers
downloads
Country
China
United States
Thailand
Malaysia
Iran, Islamic
Republic
Brazil
Taiwan
Korea, Republic
France
United Kingdom
Japan
Total
Usage
2008
151306
77093
55054
29680
22196
31737
23361
30939
28818
29733
26762
767416
%
19.7
10
7.2
3.9
2.9
Usage
2009
184154
89134
64774
43903
34960
4.1
3
4
3.8
3.9
3.5
100
39165
33118
36080
36407
32941
31524
965851
%
19.1
9.2
6.7
4.5
3.6
Usage
2010
250159
143788
80644
49424
46067
%
20.7
11.9
6.7
4.1
3.8
4.1
3.4
3.7
3.8
3.4
3.3
100
41952
41783
40361
38983
36445
35318
1210621
3.5
3.5
3.3
3.2
3
2.9
100
Hydrocolloid Materials & Function
- Gelling
• Pectin
• Alginate
• Starch
• Agar
• Carrageenan
• Gellan
• Curdlan
• Celluosics
• Mixtures
- Thickening
- Emulsification
• Pectin
• Gum Arabic
• Alginate
• Propylene Glycol Alginate
• Starch
• Sugar Beet Pectin
• Guar Gum
• OSA starch
• Xanthan
• Konjak Glucomannan
• Xanthan
• Lamda Carrageenan
Structuring Foods with
Polysaccharides
Innovation
A Couple of Eureka Moments
Oranges
Crude
pectinaceous
gelling material
with a pectin
degree of
esterification
preferably less
than 10%
Why a pectin with a very low degree of
esterification (DE)?
Change in viscosity on
autoclaving (120OC
10mins) pectin solutions of
different DEs as a function
of pH.
Pilnik, W. and MacDonald,
R.A. (1968) Gordian,
68,531
Why did pectate work and alginate
fail?
• Pectate will gel at a lower calcium
level than alginate.
• On autoclaving slight increase in
available calcium achieved calcium
level not enough to gel alginate
Pectate pulp process
Mitchell J. and Taylor, A (1983) pp 247-265 in Upgrading Waster for Food and Feed; edited
Ledward, DA et al, Butterworths, London
A short history of pectate pulp
• Developed and patented in 1938 (Wilson)
– Some production of material,
– Non-food applications explored
• New application discovered
in 1974 (Mitchell)
– Production restarted
• Food application patent runs out in 2000.
Some increased interest in material
• The future??
What is the gelling systems for the
whole product
Carrageenan
Plus
Cosynergist e.g. locust bean gum,
konjak glucomannan
Cosynergist does not normally gel on its own but
makes the carrageenan gel stronger and more
elastic
Konjak:Carrageenan Mixed Gels
The Influence of Alkaline pH
Parinda Penroj
Wunwiboon Ganjanagoonchorn
Department of Food Science and Technology
Kasetsart University, Chatuchak
John Mitchell and Sandra Hill
Division of Food Sciences, University of Nottingham, England
Konjak Glucomannan
Glucose:mannose ratio~1:1.5. 5-10% of sugar residues
acetylated
Rationale of Work
• Konjak mannan interacts synergistically
with carrageenan and xanthan in a similar
way to locust bean gum
(Morris, ER in Biopolymer Mixtures (1995) edited Harding,
S et al, Nottingham University Press)
• What happpens to this interaction when
konjak mannan deacetylates?
Series of Mars patents
claiming
thermoirreversible gels
prepared from heated
glucomannan/carrageenan
blends.
Inventors: Vernon, Cheney
and Stares
Heating Curves in Oscillation for 0.3%/0.3% Carr +
KM before and after two hours holding at 90OC
1.00E+05
1.00E+04
pH 6
1.00E+03
1.00E+02
1.00E+01
Storage modulus (Pa)
1.00E+00
10
20
30
40
50
60
Temperature (C)
70
80
90
Before holding
1.00E+05
After holding
1.00E+04
pH 8
1.00E+03
1.00E+02
Protocol:Cool>
Heat>Hold
>Cool> Reheat
1OC /min
1.00E+01
1.00E+00
10
20
30
40
50
60
Temperature (C)
70
80 90
1.00E+05
1.00E+04
1.00E+03
before holding
after holding
1.00E+01
1.00E+00
pH 10
pH10
1.00E+02
10
20
30
40
50
60
Temperature (C)
70
80 90
Critical gelling concentration (cO) for alkali gelation
of konjak mannan has been reported as 0.4% (Case
et al, 1992).
In our work we found it impossible to prepare
homogenous gels with 0.3% konjak mannan alone
under any of the conditions used yet in the presence
of carrageeenan after alkali deacetylation dynamic
rheology suggest strong gels can be prepared in the
presence of 0.3% carrageenan above the melting
point of the carrageenan helices.
WHY?
Phase Separation Model
Carrageenan
rich
Konjak
mannan rich
If modulus of konjak phase (Gk)>> modulus of carrageenan phase then
modulus of gel = Φ Gk . To achieve the observed modulus of
2x103Pa konjak phase volume has to be reduced to about 0.1
Conclusions
• On deacetylation, in the presence of carrageenan,
konjak mannan forms gels at lower concentrations
than normal.
• This may be explained on the basis of an
excluded volume effect.
• Deacetylation would be expected to occur at less
alkaline pHs on severe heat treatment (could
explain thermal irreversible gels in patent
examples)
Xanthan Gum
HOH2C
HOH2C
O
O
HO
O
O
OH
OH
COO-M+
HO
HO
H3C
O
O
HO
O
OH
+
-
M OOC
O
HO
Mw ~ 4.106 D
O
AcOH2C
O
+
+
+
M =Na , K , ½Ca
2+
O
OH
“Hydrocolloid of choice for long term
future…. Excellent opportunities both for
new products and for process improvement
on the production of existing products”
Dennis Seisun In Gums and Stabiliser for
the Food Industry 11. (2002)
Xanthan Gum Price Trend
Average price US$ per kg
year
Adapted from “Food stabilisers, thickeners and
gelling agents” ed: A Imeson, chpt 1 Introduction D.
Seisun (2010)
Stiff worm like chain
Persistence lengths
Xanthan
~120 nm
DNA
~50 nm
Alginate
5-17 nm
Chitosan
6-12 nm
Maurstad , G. et al (2003) 107, .8172
Secondary Structure
• Dihelical
• Not clear whether coaxial or side by side helices
• Denaturation temperature increases
strongly with salt content
• Because of heat treatment during recovery
process most commercial material has been
denatured and renatured .
Effect of salt concentration on xanthan
isotropic:anisotropic transition
Anisotropic
Biphasic
Xanthan
concentration
sato slide.pdf
Isotropic
Salt concentration
Sato, T and Teramoto , A (1991) Physica A 176, 72-86
Liquid Crystalline Polymers, Donald A et al Cambridge University Press
Change in viscosity across the transition (solvent 1M NaCl)
C1 C11
Viscosity
(Poise)
Xanthan concentration %
Lee H-C and Brant D.A. (2002) Macromolecules 35, 2223
Why should phase changes at xanthan
concentrations > 1% be relevant for food
applications?
Xanthan 1%
Effect of adding Alginate
Viscoelasticity at 1.02 Hz
2
G'
G"
Tan Delta
30
1.5
20
1
10
0.5
Phase separation visible
0
0
0
(Mean ± SD, n=3)
1
2
3
% (w/w) added alginate
4
5
Tan Delta
G', G" at 1.02 Hz (Pa)
40
Crossed Polarised Light Microscopy
1% Xanthan 5% Alginate
Phase Diagram
Concentrating xanthan by exclusion from
swelling starch granule
Lad, M.D. et al (2010) Gums and Stabilisers for the Food Industry 15, 126
Viscosity of 10% starch in the presence of
varying hydrocolloid concentration
6000
Final viscosity / cP
Guar
5000
4000
3000
xanthan
2000
1000
0
0
0.2 0.4 0.6 0.8
1
1.2 1.4 1.6 1.8
2
Hydrocolloid concentration / %
10% starch only
10% starch plus 2% Xanthan
low viscosity
anisotropic
xanthan phase
been swollen
starch granules?
80 um
Can positron annihilation spectroscopy provide new
insight into the role of water on polysaccharide
properties in the glassy state?
Ashraf Alam1, Javier Enrione2, Bill MacNaughtan3, John
Mitchell3 and Mina Roussenova1
1 H.H.
2 Food
3
Wills, Physics Laboratory, University of Bristol, UK
Structure Group, Universidad de Santiago de Chile
Division of Food Sciences, University of Nottingham, UK
Positron Annihilation Lifetime Spectroscopy (PALS)
22Na
decay
e+ production
prompt emission
of 1.28 MeV γ ray
4
Thermalisation and diffusion of e+
e+ + e- → Positronium (Ps)
↑↓ p-Ps
Free e+
↑↑ o-Ps
↓↓
0.12 - 0.2 ns
0.35 - 0.5 ns
1 - 4 ns (“pick-off”)
(environment dependent)
o-Ps decay
Two 511 keV γ rays
Effect of water on molecular packing of gelatin matrices
130
90
aw = 0.22
?
aw = 0.33
80
Glassy
state
70
aw = 0.44
Rubbery/ Gel
state
aw = 0.68
60
0.1
0.2
Qw
90
80
Tg
70
200
250
1.0
300
50
380
100
95
45
40
35
360
90
85
80
75
280
320
360
400
Tm
440
365.9 K
365.7 K
T (K)
30
350
400
450
321.2 K
Tg 321.4 K
340
320
300
280
a
25
270 280 290 300 310 320 330 340 350 360 370
T (K)
Tg, PALS (K)
0.0
vh (Å3)
100
Endothermal heat flow (mWg -1)
vh ( Å 3)
110
aw = 0.11
T = 298 K
3
vh ( Å )
120
100
b
260
260 280 300 320 340 360 380
T (K)
Tg,DSC (K)
Water has a complex effect on the molecular packing of the gelatin matrices.
Depending on the level of hydration it can acts as a plasticiser or an anti-plasticiser.
Dependence of free volume hole size on water
content for amorphous maltodextrin(starch) and
gelatin
120
100
gelatin
80
Mean free
volume hole
size (Å3)
60
maltodextrin
40
20
0
0
0.05
0.1
Weight fraction of water
0.15
0.2
Starch antiplasticization by water
comparison with glycerol
water
glycerol
Sala, R. and Tomka, I. (1993) pp475-482 in the Glassy State in Foods edited
Blanshard, J., and Lillford, P. Nottingham. University Press.
Reference
Sereno, N., Hill, S.E and Mitchell,J.R.
Impact of the extrusion process on xanthan gum
behaviour.
Carbohydrate Research (2007), 342: 1333
Producing Particulate Xanthan By
Extrusion
Xanthan
gum
H2 O
Heaters
Screw
Die
Sample
Twin Screw Clextral BC21 Extruder
Drying and milling
Vacuum oven (65°C) Freeze dryer (<0°C)
Fan assisted oven (90°C)
Milling to particle size
125 to 250 µm
Dispersibility of xanthan gums
Non-processed xanthan gum
Processed xanthan gum
Solutions were briefly mixed with a spoon
9
Control
Processed
CoVA prTemperature
dependence of viscosity of
processed (Hydraxan ) and control (Keltrol T)
xanthan
3500
120
Hydraxan Trial 1
3000
Hydraxan Trial 2
100
Keltrol-T Control
2500
Temp( C)
2000
60
1500
40
1000
20
500
0
0
0
2
4
6
8
10
Time (min)
Solvent: 0.2%NaCl
2% xanthan
12
14
16
18
20
Temperature( C)
Viscosity (Cp)
80
Microscopy of xanthan particles on
water addition
Non-processed xanthan gum
0 seconds
1 minute
5 minutes
0.16 mm
10 minutes
1.2 mm
Extruded xanthan gum
0 seconds
0.25 mm
1 minute
5 minutes
10 minutes
2.8 mm
Swollen Volume of Particulate Phase Obtained After Mild
Centrifugation
Typically about 10% of total
xanthan is found in the
supernatant
Effect of salt concentration and temperature on
viscosity of 0.75% physically modified xanthan
gum
4000
3500
Viscosity (Cp)
3000
2500
2000
1500
1000
500
no NaCl
0.005%
0.01%
0.02%
0.03%
0.04%
0.05%
0.10%
0.50%
1.00%
0
-500
20 25 30 35 40 45 50 55 60 65 70 75 80 85 90
Temperature (°C)
Microcalorimetry at Different Salt
Contents (0.75% xanthan)
Temperature of Viscosity Peak and
Order Disorder Transition Agree
Process Produces a Particulate Xanthan
Structure. Kinetically Trapping
Renaturation??
Xanthan “particles” result of network
formed by intermolecular helices
Molecular solution
Particle/microgel
Consequences of Particulate
Structure
• Excellent dispersibility
• Swelling of particles and hence viscosity
will be strongly salt dependent
• Above the “helix coil” transition of xanthan
particulate structure will be disrupted and
there will be a conversion to the “normal”
renatured xanthan structure.
QUESTIONS
•
•
•
•
•
Is this new?
Does the process degrade the material?
Why does the process work?
Why xanthan?
What are the applications?
The Germans (Generally) Get There First
“Now it has been shown that cooperative linkage of
β-1,4 –D glucan chains of xanthan with α-1,4 Dglucan chains of starch take also place under the
conditions of cooking extrusion
Starch (1989) 41 467-471
Effect of hydrocolloid concentration (% of maize starch) on water holding
capacity of extruded blends (Kuhn et al, Starch (1989) 41 467-471)
Typical extruder operating conditions water content ; 27% wwb;
Product temperature 140-150OC
Specific mechanical energy ~0.15 kWh/kg
Does the process degrade the
macromolecule?
CoVA prTemperature
dependence of viscosity of
processed (Hydraxan ) and control (Keltrol T)
xanthan
3500
120
Hydraxan Trial 1
3000
Hydraxan Trial 2
100
Keltrol-T Control
2500
Temp( C)
2000
60
1500
40
1000
20
500
0
0
0
2
4
6
8
10
Time (min)
Solvent: 0.2%NaCl
2% xanthan
12
14
16
18
20
Temperature( C)
Viscosity (Cp)
80
Zero shear intrinsic viscosity
Control
50.6 dl/g
Processed material
50.8 dl/g
0.2% NaCl
Temperature 25 C
No evidence for degradation
Influence of Mechanical Energy on
Molecular Weight of Wheat Starch
Meuser et al. 1992
Why does the process work?
Prism Extruder At Nottingham
Extruder layout
Water
Die (90°C)
Zone 9-10 (80°C)
Zone 8 (50°C)
Zones 2-7 (30°C)
Feed
Port
Heating Blocks
Die
Screw
Heating Blocks
7
5.5
1
2.5
79.5
Screw length (cm)
Motor
Shaft
Screw profile
Conveying elements
End extrusion
elements
Conveying
elements
Reverse elements
Half helix
elements
Inside an extruder barrel
Zone 4
Zone 7
Zone 10
Zone 2
Zone 5
Zone 8
Zone 2
Zone 6
Zone 8
Zone 10
Temp(°C)
Zone 10
400
350
120
Zone 5
Zone 7
Zone 9
Before exit die
100
80
viscosity (cP)
300
Zone 9
250
60
200
40
150
100
Zone 2
20
50
0
0
0
5
Time (min) 10
15
20
Temperature(°C)
450
Why is the extruded material fundamentally
different from xanthan modified by heating
in other ways?
Difficult to melt out xanthan ordered structure by
heating at low water contents
High ionic strength because of counter ion concentration in
limited water
Reducing solvent concentration raises a polymer melting point
Hypothesis is that as with starch extrusion high
mechanical energy (~0.5 kWh/kg in our process)
plays a major role in disrupting the ordered structure
Could explain “weak” temperature dependence of the process
Why xanthan?
Observations More Consistent with Side By Side Helices Than Coaxial
Helices
•
Some Applications
• Powder can be added to liquids containing
very low levels of salts e.g. fruit juices to
provide very rapid thickening without
mechanical stirring
• In the presence of some salt xanthan will
disperse and swell on heating giving rise to
starch type viscosity profiles.
– Dairy, sauce and soup products developed based
on this principle
Comparison of Viscosity Development
During Cooking in Product Based on Semiskimmed Milk
Conclusions
• Extruding xanthan produces a material which in
water behaves like a polyelectrolyte particle
• In comparison to the unprocessed material the
new product shows:– Excellent dispersibility
– In salt solutions thickening on heating in a
similar way to starch
• A lot still to be understood but we are getting
there
Acknowledgements
•
•
•
•
•
•
•
•
•
•
Tim Foster
Sandra Hill
Mitaben Lad
Nuno Sereno
Matt Boyd
Nuno Sereno
Val Street
Colin Melia
Sanyasi Gaddipati
Rachael Abson
Thank you for listening