The water solubility of the films, which was 80e90% at the
beginning of storage, was gradually reduced to a value of z30% in
all the film samples at day 32 (Table 1). Protein networks tend to
aggregate over time. After a first network stabilization with
hydrogen bonds, in many cases protein molecules tend to interact
forming hydrophobic interactions, disulfide and non-disulfide covalent
bonds during storage, which normally result in an increase
in the tensile resistance of the films, a reduction of their elongation
ability, and a decrease in the film water vapor permeability and
solubility