synthesis and applications of technically relevant starch

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


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.


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


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)


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 =


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)


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


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


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


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


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.


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.


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.


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


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


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


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.


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


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


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

‐

‐


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


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


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

]


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


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)


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.


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.

synthesis and applications of technically relevant starch

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