Institute for Technical and Macromolecular Chemistry – University of Hamburg1
Olayide S. Lawal 1,3, Jörg Storz 1, Manfred D. Lechner 2
and Werner -M. Kulicke 1
1Institute of Technical and Macromolecular Chemistry, University of Hamburg, 20146 Hamburg, Germany
2Institute of Physical Chemistry, University of Osnabruck,Osnabruck, Germany
3 Department of Chemical Sciences, Olabisi Onabanjo University,Ago-Iwoye, Nigeria
Synthesis and applications of technically relevant starch derivatives using new and underutilized starch resources
Institute for Technical and Macromolecular Chemistry – University of Hamburg2
Content
Distribution and economics of cocoyam and cassava
Overview of the synthetic procedure of carboxymethyl starchPossible application of carboxymethyl starch in the inhibition of retrogradation
Synthesis of cross-linked carboxymethyl starch hydrogel and thepossible application as super slurper (absorbent) and ultrasonichydrogel
Conclusion.
Institute for Technical and Macromolecular Chemistry – University of Hamburg3
439.99578.1407.38303.83162.63Price ($)
PotatoRiceMaizeCassavaCocoyamCommodity
Source: FAOSTAT United Nations Dec. 2006.
FAOSTAT: Price of cocoyam and cassava/tonne
• Cocoyam and cassava are root crops with wide distribution in the tropical countries
• Average yields of starch from cocoyam and cassava roots are 62% and 66% on dry weight basis
Institute for Technical and Macromolecular Chemistry – University of Hamburg4
O
OH O
O
HO
Na
Overview of synthetic procedure of carboxymethyl starch
(1)+ NaOH
starch
+ H2O
+
O
OH O
OH
HO
O
OH O
O
HO
Na
C
O
OCH2
Cl Na a O
OH O
O
HO
C
O
OH2C Na
+ NaCl
NaOH C
O
OCH2
Cl Na+ C
O
OCH2
HO Naa + NaCl
(2)
(3)
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The Degree of Substitution (DS)
The DSt is defined as:
if nNaOH,0 ≥ nSMCA,0
if nNaOH,0 < nSMCA,0
nSMCA = Numbers of moles of sodium monochloroacetate
nAGU = Numbers of moles of anhydro glucose unit
nNaOH = Numbers of moles of sodium hydroxide
The RE is the reaction efficiency and it is a measure of the amount of carboxymethylgroup bonded to the starch. The RE is defined as:
⋅
t
DS 100RE =
DS
0,
0,
AGU
SMCAt n
nDS =
0,
0,
AGU
NaOHt n
nDS =
Institute for Technical and Macromolecular Chemistry – University of Hamburg6
0,0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0102030405060708090100
DS
DS
nNaOH
0.8 1.0 1.2 1.4 1.6 1.8 2.0/ nAGU
RE
RE
(%)
DS, Degree of substitution based on sodium elemental analysis., RE, Reaction efficiency., nNaOH,
moles of sodium hydroxide., nAGU, moles of anhydroglucose unit.
Effect of NaOH and SMCA concentration on DS and RE
0,00,10,20,30,40,50,60,70,80,91,0
0102030405060708090100
DS
DS
0.6 0.8 1.0 1.2 1.4 1.6 1.8nSMCA/nAGU
RE
(%)
RE
DS, Degree of substitution based on sodium elemental analysis., RE, Reaction efficiency.,nSMCA, moles of sodium monochloroacetate.,
nAGU, moles of anhydroglucose unit.
sodium monochloroacetate (SMCA)sodium hydroxide (NaOH)
Institute for Technical and Macromolecular Chemistry – University of Hamburg7
0,00,2
0,40,6
0,81,0
1,21,41,61,8
DS
DS
0.08 0.10 0.12 0.14 0.16 0.18 0.2H2O/IPA
0102030405060708090100
RE
RE
(%)
DS, Degree of substitution based on sodiumelemental analysis., RE, Reaction efficiency,
IPA, Isopropyl alcohol.
Effect of water content and temperature on DS and RE
0,00,10,20,30,40,50,60,70,80,91,0
DS
30 35 40 45 50 55 60
DS
0102030405060708090100
RE
RE
(%)
Temperature (OC)
DS, Degree of substitution based on sodium elemental analysis., RE, Reaction efficiency.
water content temperature
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0 1 2 3 4 50,000,050,100,150,200,250,300,350,400,450,500,550,600,650,700,75
DS
Time (Hr)
DS
0
10
20
30
40
50
60
70
80
90
100
RE
RE
(%)
DS, Degree of substitution based on sodium elemental analysis.,RE, Reaction efficiency.
Effect of duration of reaction on DS and RE
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0,0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
DS RE
Methanol Ethanol t-Butanol Isopropanol
DS, Degree of substitution based on sodium elemental analysis., RE, Reaction efficiency.,
Effect of organic solvent media on DS and RE
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Compilation of reaction conditions used for the experiments
DSNa, Degree of substitution based on elemental analysis., DSTr, Degree of substitution based on titration., RE, Reaction efficiency.* Calculated after correction for the sodium content of the unmodified starch.
Experiment No
Organic Solvent
Time (Hr)
Temperature (OC)
nNaOH/nAGU nSMCA/nAGU H2O/ Solvent
*DSNa DSTr RE (%)
1 Isopropanol 3 60 1.62 1.39 0.08 0.89 1.10 64 2 Isopropanol 3 50 1.62 1.39 0.08 0.90 1.02 60 3 Isopropanol 3 30 1.62 1.39 0.08 0.20 0.25 14 4 Isopropanol 3 40 1.62 1.74 0.08 0.94 1.18 58 5 Isopropanol 3 40 1.62 1.39 0.08 0.67 0.73 48 6 Isopropanol 3 40 1.62 1.39 0.12 0.69 0.70 50 7 Isopropanol 3 40 1.62 1.39 0.16 1.33 0.84 96 8 Isopropanol 3 40 1.21 1.39 0.08 0.6 0.54 50 9 Isopropanol 3 40 0.81 1.39 0.08 0.28 0.35 34 10 Isopropanol 3 40 1.62 1.04 0.08 0.55 0.51 52 11 Isopropanol 3 40 1.62 0.69 0.08 0.46 0.48 66 12 Isopropanol 3 40 1.62 1.39 0.20 0.47 0.55 34 13 Methanol 3 40 1.62 1.39 0.08 0.27 0.27 19 14 Ethanol 3 40 1.62 1.39 0.08 0.44 0.45 31 15 t-Butanol 3 40 1.62 1.39 0.08 0.61 0.75 44 16 Isopropanol 3 40 1.82 1.39 0.08 0.40 0.42 29 17 Isopropanol 3 40 2.02 1.39 0.08 0.36 0.38 26 18 Isopropanol 2 40 1.62 1.39 0.08 0.59 0.65 42 19 Isopropanol 1 40 1.62 1.39 0.08 0.40 0.40 29 20 Isopropanol 4 40 1.62 1.39 0.08 0.69 0.73 50
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5 10 15 20 25 30 35 40 45Diffraction angle
unmodified starch
Carboxymethyl starch
(2θ)
Inte
nsity
Diffractogram of only one carboxymethyl starch (CM-7, DSNa, 1.33) is shown here because all the 20 cm-starches showed the same pattern
Wide angle X-ray diffraction pattern of unmodified and carboxymethyl starch.
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T e m p e ra tu re (O C )
Endo
ther
mic
hea
t flo
w
T O
T PT C∆ H = 9 .1 2 J /g
N a tiv eS ta rc h
C M P -1
7 0 7 5 8 0 8 5 9 0 9 5
The differential scanning calorimetry thermograms of native cocoyam starch and a carboxymethylated cocoyam starch
(CM‐7, DSNa, 1.33)
The differential scanning calorimetry of unmodified and carboxymethyl starch.
Institute for Technical and Macromolecular Chemistry – University of Hamburg13
4000 3500 3000 2500 2000 1500 1000 5000
5
10
15
20
25
30
35
40
W avenum ber (cm -1)1600
14261324 1017
1643
2931
Tran
smitt
ance
(%)
N a tive s tarch
C M P -1
Infrared spectra of a representative carboxymethyl cocoyam starch (CM‐7, DSNa, 1.33) and native cocoyam starch
Infrared spectra of unmodified and a carboxymethyl starch.
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13C-NMR spectrum and peak assignments of CM-7 (DSNa),full spectrum range. U, unsubstituted carbon., S,
substituted carbon.
13C-NMR spectrum and peak assignments of CM-7 (DSNa),
part is enlarged range 86-69 ppm.
13C-NMR spectra and peak assignments of Carboxymethylstarch
R = - CH2-COONa or HDepending on DS
86 84 82 80 78 76 74 72 70ppm
C4 C2S ,C3S
C2,C3U
CH2
C6s
C5
R = - CH2 - COONa or HDepending on DS
enlargedO
R O
R O O C H 2 C O O N a
O
12
3
45
6
200 180 160 140 120 100 80 60ppm
CO
C1
C6U
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O
O C H 2C O O N a
OR O
R O7 8
5
1
23
4 6
1 8 0 1 6 0 1 4 0 1 2 0 1 0 0 8 0 6 0
7 3 7 2 7 1
p p m
C - 6 u
C - 7
C - 6 s
The DEPT 135 NMR (D2O, 5000 scans) spectrum of ultrasonically degraded carboxymethylated pigeon pea starch (CMP‐1, DS 0.72). Inset,
the enlarged range of 71 – 73 ppm.
DEPT 135-NMR spectra and peak assignments of carboxymethyl starch
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DS(Na) D1 D2 D3 D4 D5 D6 D7 D30 ∆ T Unmodified 0.00 219 797 1707 2480 3065 3066 3670 4876 4657 CM-1 0.89 14.2 14.4 14.4 14.6 14.7 14.7 14.7 14.7 0.5 CM-2 0.90 14.4 14.0 14.2 14.2 14.2 14.9 14.7 14.7 0.3 CM-3 0.20 31.3 39.1 44.0 46.4 46.4 52.9 58.1 58.2 26.9 CM-4 0.94 30.6 25.1 25.3 26.8 26.8 21.3 21.3 21.6 -9.0 CM-5 0.67 12.7 13.9 13.5 13.9 14.0 14.2 13.2 13.5 0.8 CM-6 0.69 19.2 16.2 15.3 16.5 16.5 15.8 16.1 16.4 -2.8 CM-7 1.33 20.9 19.6 19.6 19.9 20.0 20.0 20.6 20.5 -0.4 CM-8 0.6 12.7 12.8 13.4 13.6 13.7 13.7 13.7 13.6 0.9 CM-9 0.28 12.3 12.6 12.7 12.7 12.8 12.8 12.8 12.8 0.5 CM-10 0.55 23.4 23.4 22.7 23.0 22.6 22.6 22.6 22.6 -0.8 CM-11 0.46 14.8 13.9 13.6 13.6 13.6 13.3 16.4 16.5 1.7 CM-12 0.47 11.1 12.1 12.2 12.2 12.2 12.0 12.1 12.2 1.1 CM-13 0.27 30.0 32.4 40.5 40.6 40.7 40.8 42.2 42.8 12.8 CM-14 0.44 46.0 45.9 44.3 45.8 45.8 47.2 47.0 48.1 2.1 CM-15 0.61 10.5 13.6 11.9 11.9 11.9 11.3 11.9 11.9 1.4 CM-16 0.40 14.2 14.3 14.7 14.8 15.1 15.7 15.7 16.1 1.9 CM-17 0.36 13.1 13.2 13.6 13.7 13.8 13.9 14.2 15.2 2.1 CM-18 0.59 10.3 10.6 10.7 10.8 10.8 10.9 10.9 10.9 0.6 CM-19 0.40 11.3 11.4 11.6 11.8 11.7 11.7 11.7 11.8 0.5 CM-20 0.69 12.6 12.6 12.4 12.4 12.4 12.3 12.2 12.4 -0.2
Sample
Effect of days of storage on paste clarity of unmodified and carboxymethylated starches
DSNa, Degree of substitution based on elemental analysis., ∆ T, Change in turbidity∆ T= D30-D1
Possible application of carboxymethyl starch in the inhibition of starch retrogradation
Storage days of starch paste
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Application of carboxymethyl starch in the preparation of super absorbent
Super absorbents are materials which exhibit outstanding absorption power for liquids but do not release the liquid on mechanical stressMost absorbents used for several applications are based on neutralized cross linked poly(acrylic acid) (PANC).Two limitations are identified: (a) The PANC products are not completely biodegradable (b) The PANC products are not from renewable resources (CO2-neutrality)Cross-linked carboxymethyl starches could be used as alternatives to the PANC productsIn addition to addressing the two aforementioned problems associated with PANC products, carboxymethyl starches have the advantage of cheaper price.Conventional super absorbent based on PANC costs 2 to 2.5 $ per kilogram while starch from cocoyam and cassava cost 0.16 and 0.3$ per kilogram.
Institute for Technical and Macromolecular Chemistry – University of Hamburg18
Synthesis of super absorbent hydrogel based on cross-linked carboxymethyl starch with a dicarboxylic acid
O
ORRO
O
O
OH
O
HO+
O
O
O
O
O
RO
OO
O
O
RO
OO
-2H2O 130 oC
Carboxymethyl starch Suberic acid
Cross-linked carboxymethyl starch
Scheme 1. Diagram showing cross linking of carboxymethyl starch with suberic acid
Na+
O
O-
Na+
O
O-
Na+
O
O-
R = H or CH2COONa
Depending on the DS
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Swelling of a super slurper
Cross‐linkingNetwork Prevent the loss of liquid
under stress
Cross‐linkingnetwork
prevents the loss of
liquid under stress
+ Liquid
Unswollen gel
Swollen gel
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H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
Na
Na
Na
Na
Na
NaNa
Na
Na
Na
+
+
++
+
+
+
+
+
+
+
+
+
+
+
+
+
‐
‐
‐
‐
‐
‐
‐
‐
‐
‐
‐
‐
‐
H2O
Cl
Cl
Cl
ClCl
Cl
Cl
Cl
Cl Cl
H2O
Na
Na
Na
Na
Na
Na
Na
NaNa
Na
+
+
+
+
+
Na
Na
Swollen gel with outside NaCl solution and Na+ and Cl- ions penetrated into the gel
‐
‐
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Cross section diagram of the apparatus for measuringabsorption under load
6
1
2
3
4567 8
9
1 = Weight2 = Cylinder3 = Teflon disc
4
4 = Absorbent
5
5 = Metal mesh
7 = Filter plate
76666
6 = Test solution
88
8 = Filter paper9 = Base
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Absorption under load and free swelling capacities of cross-linked carboxymethyl starches compared with neutralized cross-linked poly(acrylic acid) (PANC)
1939CASXBTC
1968CASXPIM
1658CASXSUB
1460CASXGLU
20-3040-54PANC
*AUL (g/g)*FSC (g/g)Absorbent
FSC: Free swelling capacity (after 1 h)
AUL: Absorption under load (after 1h)
*Measurements in NaCl solution (9 g/L)
CASXGLU: Carboxymethyl starch cross-linked glutaric acidCASXSUB: Carboxymethyl starch cross-linked with suberic acidCASXPIM: Carboxymethyl starch cross-linked pimelic acidCASXBTC: Carboxymethyl starch cross-linked with butanetetracarboxylic acid
AUL is measured under load of 460kg/m2
equivalent of 4500 Pa
Degree of substitution of carboxymethyl starch is 0.86
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Rheological Characterisation of the hydrogels indicating the storage (G’) and the loss modulus (G’’)
0,01 0,1 1 10 100100
101
102
103
104
105
100
101
102
103
104
105
CAS-X-GLUCAS-X-SUBCAS-X-PIMCAS-X-BTC
G´,
G´´
[Pa]
ω [rad·s-1]
|η∗ | [
Pa·s
]
Institute for Technical and Macromolecular Chemistry – University of Hamburg24
Network parameters of sythesized hydrogels calculatedfrom the G´p Values at ω=0,01 rad·s-1
5162.58E-085.83E+22240CAS-X-BTC3542.27E-088.50E+22350CAS-X-PIM2872.12E-081.05E+23432CAS-X-SUB2522.03E-081.19E+23491CAS-X-GLU
Molar Mass between two entanglement
points M*e
[g·mol-1]
Distance between two entanglement points ξ [m]
Cross-link densityνe [m-3]
Plateau modulus G’P [Pa]
Sample
2 Kulicke et al. Starch/Stärke 56 (2004)
Network parameters were calculated on basis of theory of rubber elasticity2
νeP AG NR T
=⋅⋅
'
( )ξ ν=−
e3
1M R T
Gep
* =⋅ ⋅
′ρ
Institute for Technical and Macromolecular Chemistry – University of Hamburg25
0,01 0,1 1 10 100100
101
102
103
104
105
100
101
102
103
104
105
Ultrasonic gel 1 (Kawasson)Ultrasonic gel 1 (NRF 13.2)CAS-X-GLUCAS-X-SUBCAS-X-PIMCAS-X-BTC
G´,
G´´
[Pa]
ω [rad·s-1]
|η∗ | [
Pa·s
]
Possible Application: Rheological behavior of carboxymethyl starches compared to synthetic ultrasonic gels
hydrogels prepared from cross-linked Carboxymethylstarch have similar rheological properties with synthetic ultrasonic gels2
2 Kulicke et al. Starch/Stärke 56 (2004)
Institute for Technical and Macromolecular Chemistry – University of Hamburg26
Conclusion
• Preparation and possible technical applications of starch derivatives based on lesser known and underutilized starch resources are reported.
• Emphasis is placed on cocoyam and cassava starches which are cheaper than conventional potato or maize starches, thus indicating lower cost of production in the industries for technical applications.
• Carboxymethyl starches inhibited turbidity of the stored starch gel, thereby making it relevant in paste clarity and inhibition of retrogradation particularly in food applications at controlled levels approved by relevant food regulation agencies.
• Environmentally friendly and less expensive super slurpers or ultrasonic gels can be prepared with cross-linked carboxymethyl derivatives of the starches.
Institute for Technical and Macromolecular Chemistry – University of Hamburg27
Acknowledgement
We acknowledge with thanks, the support of Alexander von Humboldt foundation of Germany for the award of postdoctoral fellowship withProf. Dr. W.-M. Kulicke
We thank Institute of Technical and Macromolecular Chemistry University of Hamburg and Institute of Physical Chemistry, University of Osnabruck for the provision of facilities.