Coating the sheets with chitosan led to a higher surface
roughness compared with the uncoated sheets, independently of the method used for coating. This feature may be
associated with the reaction of glutaraldehyde with
repeating units of the chitosan polymer chain due to the
cross-linking process. Furthermore, the sheets coated by
immersion showed a more irregular surface than the spraycoated samples, probably because the immersion favored
water diffusion into the starch matrix which modifies the
surface appearance of the sheet.
Gierszewska-Druzy
nska and Ostrowska-Czubenko
[16]
studied the ionic cross-linking of chitosan membranes
with sodium tripolyphosphate and observed the surface of
the films by SEM. They reported that the surface of the chitosan
films was smooth, while on the surface of the
cross-linked chitosan membrane there were numerous
visible lumps. These differences in the surface morphology
were confirmed by AFM, with calculated values for surface
roughness of 3.56 and 23.71 nm for the uncross-linked and
cross-linked chitosan films, respectively