title: Alginate/sodium caseinate aqueous-core capsules: a pH-responsive matrix.
abstract: OBJECTIVE
  Alginate capsules have several applications. Their functionality depends considerably on their permeability, chemical and mechanical stability. Consequently, the creation of composite system by addition of further components is expected to control mechanical and release properties of alginate capsules.
  
  
  METHODS
  Alginate and alginate-sodium caseinate composite liquid-core capsules were prepared by a simple extrusion. The influence of the preparation pH and sodium caseinate concentration on capsules physico-chemical properties was investigated.
  
  
  RESULTS
  Results showed that sodium caseinate influenced significantly capsules properties. As regards to the membrane mechanical stability, composite capsules prepared at pH below the isoelectric point of sodium caseinate exhibited the highest surface Young's modulus, increasing with protein content, explained by potential electrostatic interactions between sodium caseinate amino-groups and alginate carboxylic group. The kinetic of cochineal red A release changed significantly for composite capsules and showed a pH-responsive release. Sodium caseinate-dye mixture studied by absorbance and fluorescence spectroscopy confirmed complex formation at pH 2 by electrostatic interactions between sodium caseinate tryptophan residues and cochineal red sulfonate-groups. Consequently, the release mechanism was explained by membrane adsorption process. This global approach is useful to control release mechanism from macro and micro-capsules by incorporating guest molecules which can interact with the entrapped molecule under specific conditions.
authors.affiliation: Laboratoire d'Ingénierie des Biomolécules (LIBio), ENSAIA-UniversitédeLorraine, 2 avenue de la forêt de Haye, TSA 40602, 54518 Vandœuvre-lès-Nancy Cedex, France.
authors.forename: Ghazi
authors.initials: G
authors.lastname: Ben Messaoud
authors.affiliation: Laboratoire d'Ingénierie des Biomolécules (LIBio), ENSAIA-UniversitédeLorraine, 2 avenue de la forêt de Haye, TSA 40602, 54518 Vandœuvre-lès-Nancy Cedex, France. Electronic address: laura.sanchez-gonzalez@univ-lorraine.fr.
authors.forename: Laura
authors.initials: L
authors.lastname: Sánchez-González
authors.affiliation: Laboratoire d'Ingénierie des Biomolécules (LIBio), ENSAIA-UniversitédeLorraine, 2 avenue de la forêt de Haye, TSA 40602, 54518 Vandœuvre-lès-Nancy Cedex, France.
authors.forename: Adrien
authors.initials: A
authors.lastname: Jacquot
authors.affiliation: Cookal Company, 21 avenue de la Meurthe, 54320 Maxéville, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Probst
authors.affiliation: Laboratoire d'Ingénierie des Biomolécules (LIBio), ENSAIA-UniversitédeLorraine, 2 avenue de la forêt de Haye, TSA 40602, 54518 Vandœuvre-lès-Nancy Cedex, France.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Desobry
mesh_terms: D000464:Alginates / Q000737:chemistry*; D002364:Caseins / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet
chemical_list: D000464:Alginates; D002364:Caseins
keywords: Composite capsules; Electrostatic interactions; Membrane adsorption; Surface Young’s modulus; pH-responsive release