Synthesis and characterization of a low solubility edible film based on native cassava starch

Films based on cassava starch have been widely used for fruit coating; however, it is necessary to incorporate other polymers in order to improve mechanical properties, once starch only leads to highly hydrophilic films, compromising their application. In this way, a polymeric blend based on cassava starch, chitosan and gelatin was combined with a plasticizer to produce biodegradable films with satisfactory mechanical and barrier properties, in order to be used as fruit coating. The films were prepared by casting method and a statistical design of 2³ was used to evaluate the effect of each polymer and what their combinations would influence over the final product. The formation of a physical blend was confirmed by FTIR. It showed low solubility, varying (10 ± 2) % a (23 ± 4) %, Opacity ranging from (1.06 ± 0.04) to (1.55 ± 0.13) AU x nm/mm, thickness from (0.20 ± 0.01) mm to (0.44 ± 0.03) mm and water vapor transmission rate ranging from 25 ± 0.2 to 30 ± 1.4 g s^-1 m^-2. Lower amounts of starch led to more flexible, less opaque and soluble films, while the combination of higher levels of starch and chitosan was responsible for lowering films water vapor transmission rate. Thus, the films showed interesting properties for fruit surface coating.