Study on Alginate–Chitosan Complex Formed with Different Polymers Ratio

Biomaterials based on polyelectrolyte complexation are an innovative concept of coatings and packaging production to be applied in a wide range of food products. The aim of this study was to obtain and characterize a sodium alginate⁻chitosan complex material with variable degree of polyion interactions by complexation of oppositely charged polysaccharides. In order to characterize polyelectrolyte complexes, theromogravimetric analysis (TGA), dynamic mechanical thermal analysis (DMTA), nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), matrix-assisted laser desorption/ionization technique with time of flight analyzer (MALDI-TOF), and scanning electron microscopy (SEM) were performed. TGA analysis showed that thermal decomposition temperature depends on the polymer ratio (R) and thermal resistance of samples was improved by increasing chitosan dosage. Accordingly to DMTA results, polyelectrolyte complexation led to obtain more flexible and resistant to mechanical deformation materials. Comparative analysis of the FTIR spectra of single polyelectrolytes, chitosan and alginate, and their mixtures indicated the formation of the polyelectrolyte complex without addition of reinforcing substances. MALDI-TOF analysis confirms the creation of polyelectrolyte aggregates (~197 Da) in samples with R ≥ 0.8; and their chemical stability and safety were proven by NMR analysis. The higher R the greater the number of polyanion⁻polycation aggregates seen in SEM as film morphology roughness.