Impact of melt rheology on zein foam properties |
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Authors: | Thomas Gillgren Tommy Alvén Mats Stading |
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Affiliation: | (1) SIK—The Swedish Institute for Food and Biotechnology, Box 5401, 402 29 Gothenburg, Sweden;(2) Department of Materials and Manufacturing Technology, Chalmers University of Technology, 402 29 Gothenburg, Sweden; |
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Abstract: | Zein, the main protein fraction in maize, is left as a by-product from bio-ethanol production. The protein has been investigated
as a material for a long time, but mainly in the form of films. In contrast, foamed zein is presented in this article. Zein
foams may perhaps be used, e.g. as trays for biodegradable food packages or as scaffolds for tissue engineering. A batch method
for manufacturing solid foams was successfully developed, the foams being manufactured by evaporation of solvent from zein
resins. In order to be suitable for foam formation, a resin must possess gas-retaining properties, which can be predicted
by extensional rheology. The presence of plasticizer in some of the resins decreased their extensional viscosity, and this
in turn affected the foaming process. Although all the resins displayed strain-hardening behaviour, there was coalescence
of pores in all the foams. Insufficient extensional viscosity resulted in the collapse of pore walls during foam expansion.
Structure analysis showed, e.g. that most pores were elongated along the main axis of the mould in which the foams were manufactured.
The plasticizer content in the resins had no significant effect on the mechanical properties of the foams. |
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