2.5. Oxygen permeability (OP)
The oxygen permeability (OP) of the films was determined indirectly
according to the method described by Ou et al. (2005). Cells
were filled with 10 ml fresh, refined, and free antioxidant sunflower
oil, covered with the films, stored inside an incubator at
25 ± 1 C and 55% RH, and supplied with a saturated calcium nitrate
solution for 45 days. The peroxide values of the oil were measured
according to the method described by Shantha and Decker
(1994) and reported as the OP index. Prior to the experiment, the
films were conditioned at 25 C, 55% RH for 48 h.