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John Mitchell
Structuring Foods with
Polysaccharides
John.Mitchell@Nottingham.ac.uk
Countries with most Carbohydrate Polymers
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Usage % Usage % Usage %
Country 2008 2009 2010
China 151306 19.7 184154 19.1 250159 20.7 United States 77093 10 89134 9.2 143788 11.9 Thailand 55054 7.2 64774 6.7 80644 6.7
Malaysia 29680 3.9 43903 4.5 49424 4.1
Iran, Islamic Republic
22196 2.9 34960 3.6 46067 3.8
Brazil 31737 4.1 39165 4.1 41952 3.5 Taiwan 23361 3 33118 3.4 41783 3.5 Korea, Republic 30939 4 36080 3.7 40361 3.3
France 28818 3.8 36407 3.8 38983 3.2 United Kingdom 29733 3.9 32941 3.4 36445 3 Japan 26762 3.5 31524 3.3 35318 2.9
Total 767416 100 965851 100 1210621 100
- Gelling
• Pectin
• Alginate
• Starch
• Agar
• Carrageenan
• Gellan
• Curdlan
• Celluosics
• Mixtures
- Thickening
• Pectin
• Alginate
• Starch
• Guar Gum
• Xanthan
• Konjak Glucomannan
• Xanthan
• Lamda Carrageenan
- Emulsification
• Gum Arabic
• Propylene Glycol Alginate
• Sugar Beet Pectin
• OSA starch
Hydrocolloid Materials & Function
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
Department of Food Science and Technology
Kasetsart University, Chatuchak
Parinda Penroj
Wunwiboon Ganjanagoonchorn
John Mitchell and Sandra Hill Division of Food Sciences, University of Nottingham, England
Konjak:Carrageenan Mixed Gels
The Influence of Alkaline pH
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
1.00E+00
1.00E+01
1.00E+02
1.00E+03
1.00E+04
1.00E+05
1.00E+00
1.00E+01
1.00E+02
1.00E+03
1.00E+04
1.00E+05
Sto
rag
e m
od
ulu
s (
Pa
)
1.00E+00
1.00E+01
1.00E+02
1.00E+03
1.00E+04
1.00E+05
10 20 30 40 50 60 70 80 90
Temperature (C)
10 20 30 40 50 60 70 80 90
Temperature (C)
pH10
before holding after holding
10 20 30 40 50 60 70 80 90 Temperature (C)
Heating Curves in Oscillation for 0.3%/0.3% Carr +
KM before and after two hours holding at 90OC
pH 6
pH 8
pH 10
Before holding
After holding
Protocol:Cool>
Heat>Hold
>Cool> Reheat
1OC /min
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
O
OOO
O
O
O
OO
HO
O
O
HOH2C
HOOH
HOH2C
OH
AcOH2C
HOHO
+M
-OOC
OH
HO
H3C
COO-M
+
OH M+=Na
+, K
+, ½Ca
2+
Mw ~ 4.106 D
“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
sato slide.pdf
Isotropic
Anisotropic
Biphasic
Xanthan
concentration
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
Xanthan concentration %
Viscosity
(Poise)
Lee H-C and Brant D.A. (2002) Macromolecules 35, 2223
Why should phase changes at xanthan
concentrations > 1% be relevant for food
applications?
0
10
20
30
40
0 1 2 3 4 5
% (w/w) added alginate
G', G
" at
1.0
2 H
z (
Pa)
0
0.5
1
1.5
2
Tan
Delta
G'
G"
Tan Delta
Xanthan 1%
Effect of adding Alginate Viscoelasticity at 1.02 Hz
Phase separation visible
(Mean ± SD, n=3)
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
0
1000
2000
3000
4000
5000
6000
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
Hydrocolloid concentration / %
Fin
al vis
co
sity /
cP
Viscosity of 10% starch in the presence of varying hydrocolloid concentration
10% starch plus 2% Xanthan
80 um
10% starch only
Guar
xanthan
low viscosity
anisotropic
xanthan phase
been swollen
starch granules?
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. Wills, Physics Laboratory, University of Bristol, UK
2 Food Structure Group, Universidad de Santiago de Chile
3 Division of Food Sciences, University of Nottingham, UK
Thermalisation and diffusion of e+
e+ + e- → Positronium (Ps)
22Na decay e+ production prompt emission of 1.28 MeV γ ray
o-Ps decay Two 511 keV γ rays
↑↓ p-Ps 0.12 - 0.2 ns Free e+ 0.35 - 0.5 ns ↑↑ o-Ps 1 - 4 ns (“pick-off”) ↓↓ (environment dependent)
Positron Annihilation Lifetime Spectroscopy (PALS)
4
T (K)
200 250 300 350 400 450
vh (
Å3)
70
80
90
100
110
120
130a
w = 0.11
aw = 0.22
aw = 0.33
aw = 0.44
aw = 0.68
Tg
Qw
0.0 0.1 0.2 1.0
vh (
Å3)
60
70
80
90
100
?
Glassystate
Rubbery/ Gel state
T = 298 K
T (K)
270 280 290 300 310 320 330 340 350 360 370
Endoth
erm
al heat flow
(m
Wg
-1)
25
30
35
40
45
50
321.2 K321.4 K
365.9 K365.7 K
Tg,DSC
(K)
260 280 300 320 340 360 380
Tg
, P
AL
S
(K
)
260
280
300
320
340
360
380
a b
T (K)
280 320 360 400 440
vh (
Å3)
75
80
85
90
95
100
Tm
Tg
Effect of water on molecular packing of gelatin matrices
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
Mean free
volume hole
size (Å3)
Weight fraction of water
0
20
40
60
80
100
120
0 0.05 0.1 0.15 0.2
gelatin
maltodextrin
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.
Sereno, N., Hill, S.E and Mitchell,J.R.
Impact of the extrusion process on xanthan gum
behaviour.
Carbohydrate Research (2007), 342: 1333
Reference
Producing Particulate Xanthan By
Extrusion
H2O
Xanthan gum
Heaters
Sample
Die
Screw
Twin Screw Clextral BC21 Extruder
Drying and milling
Milling to particle size
125 to 250 µm
Fan assisted oven (90°C)
Vacuum oven (65°C) Freeze dryer (<0°C)
Dispersibility of xanthan gums
9
Non-processed xanthan gum
Processed xanthan gum
Solutions were briefly mixed with a spoon
Control
Processed
0
20
40
60
80
100
120
0
500
1000
1500
2000
2500
3000
3500
0 2 4 6 8 10 12 14 16 18 20
Tem
pera
ture
( C
)
Vis
co
sit
y (
Cp
)
Time (min)
Hydraxan Trial 1
Hydraxan Trial 2
Keltrol-T Control
Temp( C)
Solvent: 0.2%NaCl 2% xanthan
CoVA prTemperature dependence of viscosity of processed (Hydraxan ) and control (Keltrol T)
xanthan
Microscopy of xanthan particles on
water addition
0.16 mm 1.2 mm
0 seconds 1 minute 5 minutes 10 minutes
Non-processed xanthan gum
Extruded xanthan gum
0 seconds 1 minute 5 minutes 10 minutes
0.25 mm 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
-500
0
500
1000
1500
2000
2500
3000
3500
4000
20 25 30 35 40 45 50 55 60 65 70 75 80 85 90Temperature (°C)
Vis
co
sit
y (
Cp
)
no NaCl
0.005%
0.01%
0.02%
0.03%
0.04%
0.05%
0.10%
0.50%
1.00%
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
Starch (1989) 41 467-471
“Now it has been shown that cooperative linkage of
β-1,4 –D glucan chains of xanthan with α-1,4 D-
glucan chains of starch take also place under the
conditions of cooking extrusion
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?
0
20
40
60
80
100
120
0
500
1000
1500
2000
2500
3000
3500
0 2 4 6 8 10 12 14 16 18 20
Tem
pera
ture
( C
)
Vis
co
sit
y (
Cp
)
Time (min)
Hydraxan Trial 1
Hydraxan Trial 2
Keltrol-T Control
Temp( C)
Solvent: 0.2%NaCl 2% xanthan
CoVA prTemperature dependence of viscosity of processed (Hydraxan ) and control (Keltrol T)
xanthan
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
Die
Feed Port
Water
Heating Blocks
Screw length (cm)
79.52.515.57
Zones 2-7 (30°C)Zone 8 (50°C)Heating Blocks
Zone 9-10 (80°C)Die (90°C)
MotorShaft
Screw
Screw profile
Conveying elements
Half helix
elements
Reverse elements Conveying
elements
End extrusion
elements
Inside an extruder barrel
Zone 2 Zone 4
Zone 8 Zone 10
Zone 5 Zone 7
0
20
40
60
80
100
120
0
50
100
150
200
250
300
350
400
450
0 5 10 15 20
Tem
pe
ratu
re(°
C)
vis
cosi
ty (
cP)
Time (min)
Zone 2 Zone 5Zone 6 Zone 7Zone 8 Zone 9Zone 10 Before exit dieTemp(°C)
Zone 2
Zone 9
Zone 10
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 Semi-
skimmed 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
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