Conventional plastic materials accumulation has led to a constant search to develop friendly packaging, edible coatings from biopolymers are an example. Since different proteins have different behavior and plastizicer compatibility, in this work, the effect of different polyalcohols (glycerol, sorbitol, maltitol, mannitol, and xylitol) as plasticizers on squid protein films behavior was studied. The results show that except for mannitol, transparent, and flexible films can be obtained. None of them showed transmission to light on the ultraviolet (UV) spectrum. However, only glycerol and sorbitol were sufficiently flexible to evaluate their mechanical properties, in which glycerol had a more elastic behavior with an elongation at a break of 920% and tensile strength (TS) of 0.94 MPa, while sorbitol exhibited a more plastic behavior with an elongation at break of 511% and a TS of 4.41 MPa. Water-vapor transmission rate was higher in glycerol, with 194.41 g·m⁻²d⁻¹, while sorbitol had 44.27 g·m⁻²d⁻¹ but presented blooming. This could be due to low interaction between sorbitol and the protein matrix, correlating with the film-solubility results. Amide I band of the Fourier transform infrared (FT-IR) spectra demonstrated higher denaturation and loss of alpha helical structure in glycerol film, followed by maltitol/sorbitol, xylitol, mannitol, and the control film. This in accordance with thermogravimetric analysis (TGA) results. The results of this study prove that only glycerol and sorbitol are suitable to obtain a see-through flexible film.

Protein-based films are promising biodegradable materials, but their performance is often limited by structural instability during storage. In this study, blend films were developed from myofibrillar proteins of giant squid (Dosidicus gigas) and whey protein concentrate (WPC) to improve functional properties and evaluate stability during three months of storage. The effects of plasticizer type (glycerol or sorbitol) and WPC concentration (5–15%) on film structure and performance were analyzed using Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetric Analysis (TGA), optical measurements, solubility, and water vapor transmission rate (WVTR). FT-IR revealed a transition from α-helix to β-sheet structures, indicating stronger protein–protein interactions, particularly in sorbitol-plasticized films. This structural organization improved barrier properties, reducing WVTR from 44.2 g·m⁻²·d⁻¹ in squid protein films to 18.9 g·m⁻²·d⁻¹ in films containing WPC. Light transmittance analysis showed that all films acted as effective UV barriers, with transmission starting near 350 nm. At this wavelength, transmittance ranged from 5–17% in sorbitol-plasticized films to 33–46% in glycerol-plasticized films. Increasing WPC concentration also reduced film solubility, indicating the formation of a more compact protein matrix. During three months of storage, FT-IR spectra revealed changes in the Amide A and Amide III bands associated with plasticizer migration and increased protein–protein interactions. Transparency increased during storage, indicating progressive structural reorganization, while the UV barrier properties remained stable. These results demonstrate that blending squid and whey proteins, particularly with sorbitol as plasticizer, produces biodegradable films with improved barrier properties and good structural stability during storage, highlighting their potential for sustainable food packaging applications.