net could explain why crosslinked alginate films are a better barrier
to water vapor (Olivas & Barbosa-Cánovas, 2008). Thus, ionic
crosslinking reduced the amount of water vapor moving through
the film matrix (Rhim, 2004).
The WVP of the films decreased substantially (p < 0.05) with an
increase in the crosslinking agent concentration (Table 2). Rhim
(2004) studied the effect of different concentrations of CaCl2 on
the WVP of alginate films and found, as in this study, that the WVP
decreased with increasing concentration of the crosslinking solution.
The reason may be an increase in the degree of crosslinking of
the films with high concentrations of CaCl2 in a certain range. However,
the WVP values obtained in this experiment were two orders
of magnitude lower than those reported by Rhim (2004). These differences
may be explained by the thickness of the films. The film
thickness in this study was only one-fifth of that in the literature.
For the same concentration of crosslinking agent, the thinner alginate
films reacted with Ca2+ reached saturation faster and had a
higher degree of crosslinking; therefore, the WVP of the film was
lower than that of the reference.
As Table 3 shows, with increasing crosslinking time, the WVP
of the films increased. Pavlath et al. (1999) explained this occurrence
as resulting from the dynamic process of the crosslinking
reaction;i.e., with increased crosslinking time,the internal alginate
continued to dissolve, resulting in an increase in the WVP.