The gelatin film-forming solution was prepared by dissolving dry
gelatin in distilled water (4% w/v) at 40 °C, adding sorbitol (15 g/100 g
gelatin) plus glycerol (15 g/100 g gelatin) as plasticizers. Gelatin–LS
films were prepared by mixing the dissolved gelatin with LS at a ratio
of 80–20 (calculated on dry matter content). The mixtures were stirred
at 40 °C for 30 min. The films were made by casting an amount of
40 mL over a plate measuring (12 × 12) cm2 and drying at 45 °C in a
forced-air oven for 15 h to yield a uniform thickness of 100 mm ±
10 mm. Prior to the initial analyses, the films were conditioned over a
saturated solution of KBr at 21 °C in desiccators for 2 days