Edible films and coatings are produced from edible biopolymers and food-grade
additives. Film-forming biopolymers can be proteins, polysaccharides (carbohydrates
and gums), lipids, or a mixture of these (Gennadios et al., 1997) (see
Figure 9.1). Plasticizers and other additives are combined with the film-forming
biopolymers to modify the physical properties or other functionality of the edible
films. Biopolymers have multiple film-forming mechanisms, including intermolecular
forces such as covalent bonds (e.g., disulfide bonds and crosslinking) and
electrostatic, hydrophobic, or ionic interactions. For the resulting films or coatings
to be edible, the film-forming mechanism involved in fabrication should be an
appropriate food process—namely, pH modification, salt addition, heating, enzymatic
modification, drying, use of food-grade solvents, or reactions with other
food-grade chemicals. The control of fabrication process conditions is very important
because the changes in treatment conditions can alter kinetics and reaction
mechanisms (Guilbert et al., 1996, 1997).