Comparison of Different Methods of Crosslinking Sodium Caseinate Films

PEREDA, MARIANA; MARCOVICH, NORMA E.; ARANGUREN, MIRTA I.

Siegel

Congreso; POLYCHAR18 - World Forum on Advanced Materials; 2010

The goal of this work was to investigate different methods to crosslink sodium caseinate (NaCas) films, by analyzing and comparing the final properties of the films (potentially useful as food packaging): mechanical, water vapor sorption and permeability. The crosslinking chosen methods were: a) use of glutaraldehyde (GTA) as chemical crosslinker, b) thermal treatment, c) complexation with a polysaccharide (chitosan, Chit). The films were obtained by a casting/solvent evaporation method from dilute aqueous solutions, using glycerol (28 wt%) as plasticizer. The first method (a) was followed by measuring the total soluble material (TSM), which indicated that the level of crosslinking increases as glutaraldehyde content increases. Visual inspection of the films showed a more intense yellow coloration as glutaraldehyde content was increased, due to the crosslinking reaction, which proceeded via Schiff-base formation.1 Tensile and thermal degradation (TGA) properties, as well as water vapor permeability, were measured to characterize the films. Thermal gravimetric analysis showed an increase of about 15 ºC in the initial degradation temperature due to GTA crosslinking, indicating improved thermal stability of the films. Final properties showed not much improvement at concentrations below 10 wt.% with respect to those of the uncrosslinked film. This was explained as the result of the disruption of the strong H-bonding interactions present in neat caseinate films, which was barely compensated by the introduction of low amounts of covalent SC-GTA bonds.