3.4. Light transmission and transparency
Optical properties are essential to define the ability of films and coatings to be applied over a food surface, since these affect the appearance of the coated product, which is an important quality factor (Pereda et al., 2012). Light transmission and transparency of all films at selected wavelengths are shown in Table 2. In the UV range of 200–280 nm, gelatin and blend films exhibited excellent UV barrier properties, which cause oxidative deterioration of packaged foods, leading to nutrient losses, discoloration and offflavors (Martins et al., 2012). This result is in agreement with previous reports on gelatin-based films (Jiang et al., 2010). They both indicate that protein-based films are considered to have high UV barrier properties, owing to their high content of aromatic amino acids which absorb UV light. Light transmission of Ch films was negligible at 200 nm, but was relatively high at 280 nm (54.7%).