Mechanical Properties of Thermo-moulded Biofilms in Relation to Proteins/Starch Interactions
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The effects of hydrophilic and hydrophobic characteristics of proteins on the interactions with corn starch were investigated in this study. The model system included corn starch and proteins, i.e. zein, gliadin, gluten, soy protein and rapeseed protein. The blend films were prepared by thermo-moulding in gentle conditions at 70 °C in order to avoid starch gelatinization, with respect to water content, and avoid protein denaturation. The effects of different kinds of proteins on structure and mechanical behaviour of blend biomaterials were characterised by scanning electron microscopy (SEM) and tensile test, respectively. The effects of different kinds of proteins on intermolecular interactions between proteins and starch were investigated by dynamical mechanical thermal analysis. Based on the solubility measurement results, almost all protein films showed the similar solubility to the natural protein powders, resulting from the weak influence of mild thermo-moulding treatment on protein inner structure. Different morphologies were observed for different proteins and corresponding blends, which are relatively loose protein architecture that appeared for hydrophobic protein and blend films, and uniform and densely packed architecture for hydrophilic ones. Moreover, different mechanical behaviours were obtained for different proteins and corresponding blends. No significantly increased strength for hydrophilic protein blends with starch added can be explained that there is weak intermolecular interaction between both components based on SEM observation. However, the addition of corn starch granules in hydrophobic protein networks was assumed that starch destroyed or weakened the protein network, resulting in the decrease of mechanical strength.
KeywordsProtein Corn starch Intermolecular interaction Solubility Zein
M. Zeng is grateful to Pays de la Loire Regional Council and China Scholarship Council (CSC) for post-doctoral fellowship, and acknowledges the SRF for ROCS, State Education Ministry, P. R. China, the Fundamental Research Funds for the Central Universities, China University of Geosciences (Wuhan) (contract grant number CUGL090223), and the major grant of the State Key Laboratory of Geological Process and Mineral Resources (contract grant number GPMR200918).
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