Investigating the effect of film preparation method (composite or laminated) and biopolymers’ proportion on the physicochemical properties of active chitosan-whey protein isolate film by response surface method (RSM)

The aim of this research was to investigate the feasibility of composite and laminated chitosan (CH) and whey protein isolate (WPI) film preparation which was containing cumin essential oil and chitosan nanofiber. Production of composite film was possible by decreasing WPI pH to below its isoelectric pH. Double-layer was also prepared by pouring WPI solution on dried CH film. amount of active agent and nanofiller was fixed (125 mg/100ml) and only the effect of CH/WPI ration and film type (laminated or composite) on the properties of films was arudied by RSM analytical method. The color, watercontact angle, moisture absorption, solubility, water vapor permeability and mechanical properties of films were determined. By using desirability function and according to the results, optimum formulation of composite film (65.14% WPI and 34.85% CH) and laminated film (49.01% WPI and 50.99% CH) was achieved. Microstructure of optimized films was analyzed by FTIR, FE-SEM and XRD tests. Results of FE-SEM indicated a heterogenous stracture in composite film but without any phase separation. Also, at the laminatred film good attachment between two layers of CH and WPI was observed. Semi-crystalline stracture of composite film was approved by XRD analysis and there was no detectable difference between peak intensity and crystalline stracture of composite and laminated film. there was a slight difference in the FTIR spectra of composite and laminated films. According to the results, the characteristics of composite film in comparison to laminated film had better accordance with the used prediction model. But the laminated film exhibited better morphological characteristics and could be suggested for preservation of different foods due to its high potential for use in food packaging.