Optimized pH-responsive film based on a eutectic mixture-plasticized chitosan.

Chitosan (CS, 2g/100mL)/curcumin 1g/100mL in acetic acid aqueous solution were used to prepare films to be used as food indicator. Microcrystalline cellulose (MCC) and a eutectic mixture (DES) were incorporated as reinforcing and plasticizing agents, respectively. The MCC content (133 mas%) and DES composition (7.93 mass%), based on CS dry mass, were optimized. The properties of the DES-plasticized film were compared to those for the unplasticized and glycerol (G)-plasticized CS films. The DES-plasticized film presented initial temperature of thermal decomposition at 267.7°C, dynamic glass transition at 149.3°C, water vapor permeability of 7.21×10-10gs-1m-1Pa-1, water solubility of 3.07% and stress at break of 20.1MPa. The incorporation of MCC contributed to increase the crystallinity of the composite films. Colorimetric tests, carried out in aqueous environments for the DES-plasticized film, revealed accentuated color changes, mainly at pHs higher than pH 8.