The production of biodegradable materials from renewable biopolymers, such as proteins, provides an attractive alternative, at least for some applications, to synthetic polymers, whose accumulation contributes greatly to environmental pollution. The functionality of protein films is determined by their microstructure, which characteristic varies significantly depending on the initial protein structure and the preparation method (Denavi, et al., 2009). All four aspects of protein structure (primary, secondary, tertiary, and quaternary) determine fundamentally the ability of protein chains to interact with each other as well as with other components of the formulation under consideration. The type and number of interactions involved in the stabilization of a proteinaceous matrix (disulfide covalent bonds, hydrogen bonding, electrostatic attractions, and hydrophobic bonding) is determined by the amino-acid composition and molecular weight of the proteins under consideration (which characteristics can vary significantly for different proteins) as well as by the experimental parameters used in film preparation. The protein–protein interactions involved in film formation determine the degree of cross-linking and the hydrophylic-hydrophobic character of the films and also correlate with the latter's physicochemical, mechanical, and barrier properties (Mauri and Añón, 2006 and Mauri and Añón, 2008).