Process optimization and characterization of composite biopolymer films obtained from fish scale gelatin, agar and chitosan using response surface methodology

This work is intended to optimize the composition of marine-based biopolymers for desirable packaging material properties. The quantity optimization was sought by empirical response surface methodology. To achieve the goal, Box–Behnken model was applied to the concentration of three independent variables, viz. gelatin (1.0–2.0% w/v), agar (1.0–2.0% w/v) and chitosan (1.0–2.0% w/v). Glycerol was used as a plasticizer and kept constant (25% w/w to total solid mass). The overall desirability function fits with the quadratic model at a 100% level of significance for the optimization of gelatin (1.98% w/v), agar (1.98 w/v) and chitosan (1.94% w/v) to reach minimum water vapor permeability and maximum tensile strength, elongation at break and puncture resistance. The absolute residual error (1.77 to 4.40%) of the experiment and the predicted responses were also validated. The thermal stability (TGA), crystalline structures (XRD), molecular interactions (ATR-FTIR) and topography (AFM) showed that the resultant GAC composite film has a gray color (WI), improved transparency (T) and suitable mechanical strength (WVP, TS, EB and PR) due to existence of hydrogen bonds in uniform granular network and crystallization pattern. The gelatin and agar were supported by chitosan for the reasonably acceptable film properties.