Water Vapor Absorption and Permeability of Films Based on Chitosan and Sodium Caseinate

M. PEREDA; N. E. MARCOVICH; M. I. ARANGUREN

San Nicolás, Buenos Aires, Argentina

Congreso; 7º Congreso Binacional de Metalurgia y Materiales, SAM-CONAMET 07; 2007

SAM-CONAMET

The objective of this work is to manufacture and characterize edible films made from sodium caseinate and chitosan, with an envisioned application as a protective layer on foods. Glycerol was used as plasticizer, and the films were obtained by a casting/solvent evaporation method. Moisture sorption kinetics and water vapor permeability (WVP) were investigated. The effect of different glycerol concentration on WVP measurements for chitosan and caseinate films were determined at 25º C, using a relative humidity (RH) gradient (internal: external) 0:64.5. Experimental data were fitted using a two parameter exponential growth equation. WVP increased with increasing glycerol content in both films, being chitosan samples much more permeable than caseinate ones at any glycerol content. WVP of caseinate, chitosan and chitosan/sodium caseinate films with 28 % wt./wt. glycerol were also determined for two RH gradients: 0:64.5 and 100:64.5, obtaining higher WVP with increasing humidity, and, both chitosan and caseinate films showed a similar increment of WVP with respect to those obtained at 0:64.5. Moisture sorption kinetics of caseinate films with different glycerol content in 75 % RH was determined. Peleg model was used to predict the moisture sorption behavior over the entire time period, providing a good fit to the experimental data.