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Influence of temperature and mechanical energy input on the structure of wheat gluten bioplastics.
M.-H. Morel, A. Redl, and S. GUILBERT. Unit of Cereal Technology and Agropolymers, ENSA.M-INRA, 2
Place Viala, 34060 Montpellier cedex 1, France.
The work was devoted to the analysis of the biochemical and
rheological changes that may occured during thermo-plastic processing of plasticized wheat gluten (100/54,
gluten/glycerol). Glycerol-gluten blends were mixed at 100 rpm at various temperatures of regulation of the
mixer vessel (40, 60 and 80°C) in order to obtain samples with different thermal and mechanical energy
history. Rheological properties of samples were investigated in oscillatory shear mode and the obtained
mechanical spectra were quantified using Cole Cole distributions. Changes in the size distribution of the
total gluten protein were sudied by SE-HPLC. Thiol/disulfide status was measured using Ellman's reagent.
All rheological and biochemical data appeared more related to thermal energy than to the mechanical
energy input. Change of gluten structure during mixing was assessed by increase of the plateau modulus G
and decrease of protein solubility in SDS solution, with mixing time and temperature. The results revealed
the formation of an increasing number of disulfide bonds between wheat proteins during mixing wich
enhanced the elastomeric behavior of gluten material. Increase in G and decrease in protein extractability
followed an Arrhenius-type law, with activation energy (Ea) of 29 kJ/mol. Compared with
Ea of thermal denaturation of wet gluten (145 kJ/mol) this low value suggests that mechanical
energy enhances the denaturation process.
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