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 degradation I II III IV zein-25%PEG400, 50rpm Heating 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 utilized T1=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. T1T2T3T4Profile

Zein, 25%PEG400 Extrusion process

Zein vs stearic acid Extrusion process

Kafirin from batch 4 does not thermoplasticize like batch 2 Different plasticizers and experimental conditions were used Mixing process of Kafirin

Tensile properties of extruded zein films

Plasticizer  R (MPa)  R (mm/mm) E (MPa) PEG    Stearic acid   

Water permeability of extruded zein films

Oxigen permeability of extruded zein films

Kafirin-mechanical properties T  R (MPa)  R (mm/mm) E (MPa) 30°C 3.31    °C 4.77    °C 2.97    12.02

Kafirin-mechanical properties Plasticizer type  R (MPa)  R (mm/mm) E (MPa) PEG    Lactic acid 1.48    6.37

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!!!