Mise en place d'une approche multi-méthodologique de l'étude de la complexation et de la coacervation complexe entre protéines et polysaccharides

Abstract : A multi-methodological approach coupled with slow in situ acidification was used to determine pH-induced structural and morphological transitions during complexation and complex coacervation between j3-lactoglobulin (BLG) and Acacia gum (AG). First soluble complexes were formed at pHsc (4.9) induced by the neutralization of AG negative charges by positively charged BLG. A loss of 0;- helix structure of the protein was observed at pHpct (4.8) after first interactions between BLG and AG occur. Soluble complexes aggregated at pHca (4.7) then, evolved toward a transition pH region between BLG/AG complexation and coacervation, comprised between pHpSi (4.4) and pHps (4.2). The increase of BLG positive charges induced interactions of complexed BLG with other AG molecules, involved or not in complexes. Aggregated complexes formed clusters at pHpSi inducing an irreversible destabilisation of the system, which separated at pHps. Higher order aggregation of complexes and phase separation were controlled by charge neutralization of complexes induced by the decrease of negative charges of AG complexed or free. Destabilisation of mixed dispersion was controlled by a critical size/charge ratio parameter. This could explain that large-scale aggregation of complexes and coacervation Gan occur without the requirement of aggregate neutrality. Clusters of aggregated complexes were identified as "critical nuclei" initiating the nucleation and growth, which was identified as the dynamic mechanism of complex coacervation between BLG and AG. At microscopically level, first coacervates appeared at pHcoa (4) near the maximum of turbidity. Their size grew with coalescence phenomenon. A gain in BLG secondary structure was observed near pHcoa.
Document type :
Theses
File URL :
http://docnum.univ-lorraine.fr/prive/INPL_T_2005_MEKHLOUFI_G.pdf
Complete list of metadatas

https://hal.univ-lorraine.fr/tel-01749996
Contributor : Thèses Ul <>
Submitted on : Thursday, March 29, 2018 - 12:35:23 PM
Last modification on : Monday, April 16, 2018 - 10:41:19 AM

Identifiers

  • HAL Id : tel-01749996, version 1

Collections

Citation

Ghozlene Mekhloufi. Mise en place d'une approche multi-méthodologique de l'étude de la complexation et de la coacervation complexe entre protéines et polysaccharides. Alimentation et Nutrition. Institut National Polytechnique de Lorraine, 2005. Français. ⟨NNT : 2005INPL008N⟩. ⟨tel-01749996⟩

Share

Metrics

Record views

7