Complexation of chitosan with gum Arabic, sodium alginate and κ-carrageenan: Effects of pH, polymer ratio and salt concentration

• Published in: Carbohydrate polymers Vol. 223; p. 115120
• Main Authors: Rabelo, Renata S., Tavares, Guilherme M., Prata, Ana S., Hubinger, Miriam D.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.11.2019
• Subjects: Associative phase separation; Complex coacervation; Electrostatic complexes; Isothermal titration calorimetry; Electrostatic complexes; Associative phase separation; Complex coacervation; Isothermal titration calorimetry
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2019.115120

[Display omitted] •The complexation of chitosan with anionic polysaccharides presented ΔH<0 and ΔG<0.•Sulfated polymer interacted more strongly with chitosan than with carboxylated polymers.•The phase separation of the complex of chitosan with gum Arabic was reversible.•The complex of chitosan with alginate was the least sensitive to the presence of NaCl. The effects of pH, ionic strength and polymer ratio in the complexation of chitosan (CHI) with different anionic polysaccharides, namely gum Arabic (GA), sodium alginate (ALG) and κ-carrageenan (CRG), were investigated. This was made using titration techniques, which allowed the determination of stoichiometry and binding constant of complexes. The sulfated polysaccharide interacted more strongly with CHI than carboxylated polysaccharides. The increase of ionic strength (0–100 mM NaCl) in the polysaccharides complexation resulted in a significant reduction in the binding constant of GA:CHI and CRG:CHI, but did not influence the complexation of ALG with CHI. The pH and polymer ratio affected the formation and solubility of complexes GA:CHI, while for ALG:CHI and CRG:CHI, insoluble complexes were observed in all pH and polymer ratio evaluated. A phase transition of coacervate to gel was proposed to ALG:CHI and CRG:CHI, which can be related to the self-association of anionic polymers, when these are in excess.