Thermoplasticization of zein and kafirin

IMCB-CNR

November 2004

Processing condition for extrusion

I. Increase of viscosity due to plasticization

II. Decrease of viscosity due to the increase of T

III. Increase of viscosity due to further plasticization and/or chemical reactions

IV. Decrease of viscosity due to the increase of T and degradation0

200

400

600

800

1000

1200

40 60 80 100 120 140 160

Tq

(N

cm)

T (°C)

III

III

IV

zein-25%PEG400, 50rpmHeating rate: 10°C/5min

The second peak does not depend on rpm

Extrusion of zein

Materials and procedures

Zein/PEG 400 or zein/stearic acid were mixed before feeding

The following T profiles were utilizedT1=30°C, T2=60°C, T3=T4=65°C, 70°C, 75°C, 80°C, 85°C.

For each profile the rotational speed of the screws were: 20, 40, 80 e 120 rpm.

T1 T2 T3 T4Profile

Zein, 25%PEG400

Extrusion process

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0 5 10 15 20 25

Tq (Nm)

rpm

T (°C)

Time (min)

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0 400 800 1200 1600 2000 2400 2800 3200

TQ (Nm)

rpm

T (°C)

Time (sec)

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0 1000 2000 3000 4000 5000

TQ (Nm)

rpm

T (°C)

Time (sec)

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0 500 1000 1500 2000 2500

TQ(Nm)

R1

T4

Time (sec)

Zein vs stearic acid

Extrusion process

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80

0 5 10 15 20 25

Tq (Nm)

rpm

T (°C)

Time (min)

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140

0 4 8 12 16

Tq (Nm)

rpm

T (°C)

Time (min)

Kafirin from batch 4 does not thermoplasticize like batch 2

Different plasticizers and experimental conditions were used

Mixing process of Kafirin

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0 2 4 6 8 10 12

Tq (Nm) B4

Tq (Nm) B2

T (°C) B4

T (°C) B2

Time (min)

Tensile properties of extruded zein films

200

400

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1400

0 20 40 60 80 100 120 140 160

70°C

75°C

80°C

screw speed (rpm)

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5

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0 20 40 60 80 100 120 140

70°C 75°C 80°C

screw speed (rpm)

Tensile properties of extruded zein films

0

0,05

0,1

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0,2

0,25

0 20 40 60 80 100 120 140

70°C75°C80°C

screw speed (rpm)

Tensile properties of extruded zein films

Plasticizer R (MPa) R (mm/mm)

E (MPa)

PEG 400 8.060.48 0.110.0015 516.8445.16

Stearic acid 17.916.33 0.0230.016 130262.285

Water permeability of extruded zein films

0.00E+00

5.00E-08

1.00E-07

1.50E-07

2.00E-07

2.50E-07

3.00E-07

0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90Water activity

Wat

er P

erm

eabilit

y

Extruded 20 rpm

Extruded 40 rpm

Extruded 80 rpm

Extruded 120 rpm

Casting - PEG

Oxigen permeability of extruded zein films

0.00E+00

2.00E-07

4.00E-07

6.00E-07

8.00E-07

1.00E-06

1.20E-06

0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90

Water activity

Oxyg

en P

erm

eabilit

y

Extruded 20 rpm

Extruded 40 rpm

Extruded 80 rpm

Extruded 120 rpm

Casting - PEG

Kafirin-mechanical properties

0

1

2

3

4

5

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8

30°C38°C45°C

Strain (mm/mm)

T R (MPa) R (mm/mm

)

E (MPa)

30°C 3.310.43 0.690.12 157.7440.14

38°C 4.770.44 0.680.13 172.3313.11

45°C 2.970.56 0.720.12 107.9612.02

Kafirin-mechanical properties

0

0,5

1

1,5

2

2,5

3

3,5

4

0 0,5 1 1,5

Acido lattico

PEG 400

Strain (mm/mm)

Plasticizer type R (MPa) R (mm/mm) E (MPa)

PEG 400 2.970.56 0.720.12 107.9612.02

Lactic acid 1.480.11 1.170.25 38.546.37

Film blowing process

Film blowing process

Film blowing process

The protepack…edible??

Fiber spinning

Foams with CO2

Conclusions on zein

• Zein (from Aldrich) can be thermoplasticized directly in the extruder

• Extrusion parameters are correlated to mixing process parameters

• The mechanical properties of extruded zein varied with the extrusion conditions. The variation in oxigen and water permeability was not relevant.

• Residence time and T must be optimized to get melt with good rheological properties

• Preliminary results showed that, in certain conditions, the elongational properties of zein are suitable for film blowing and fiber spinning.

Conclusions on kafirin

• From FTIR (Peter) analysis batch 2 and batch 4 contained different amount and alfa-helix and beta-sheets.

• When compated to batch 2, the termoplasticization of batch 4 required a higher amount of plasticizer (30% instead of 25%) and lower T (45°C instead of 60°C)

• The higher amount of plasticizer required leaded to melt with poor rheological properties, not suitable for film blowing. However, the amount of kafirin available was not enough to optimize process parameters.

• We believe kafirin films can be obtained but need a lot….sorry!!!