Effect of the Mixture of Polymers on the Rheological and Technological Properties of Composite Films of Acoupa Weakfish ( Cynoscion acoupa ) and Cassava Starch ( Manihot esculenta C. )

Biopolymers, such as proteins and carbohydrates, can be used for the production of biofilms, as they are biodegradable, biocompatible, and capable of providing adequate technological characteristics for films. This study aimed to evaluate the influence of different concentrations of fish myofibrillar proteins and cassava starch on the rheological and technological properties of filmogenic solutions (FS) and films. FS were prepared with 1% protein (fish residue) (F1), 4% starch (F2), 0.5% protein + 2% starch (F3), 1% protein + 2% starch (F4), and 0.5% protein + 4% starch (F5) all with 30% glycerol. Rheological analyzes of apparent viscosity were performed on the filmogenic solutions and were evaluated the technological properties, thermogravimetric (TGA/DTG and DSC), x-ray diffraction, infrared spectroscopy (FTIR-ATR), microscopy (SEM), and spectroscopy (EDS) in elaborate films. The FS showed a non-Newtonian behavior ( n ≠ 1), with dilating and pseudoplastic fluids for proteins and starch, respectively, both model Herschel-Bulkley. The color of the raw materials influenced the color of the films ( p ≤ 0.05). Composite films (F3, F4, and F5) showed better barrier properties in the visible range (350–800 nm), with starch (F1) being the most transparent ( p ≤ 0.05). F4 film showed the best technological properties: PVA, solubility and mechanics. The films with the highest percentage of protein, F1 and F4, presented higher ( p ≤ 0.05) thermal resistance. In addition, starch favored the crystallinity of films (F3, F4, and F5), providing more orderly matrices. The FTIR and EDS analyzes of the films confirmed the successful interaction of proteins and starch. Therefore, the properties of the elaborated composite films indicate that the interaction between biopolymers is positive to produce packaging for different types of food.