Edible and biodegradable films are made of renewable resources, offer an alternative to synthetic plastics for packaging, and, unlike these, can be placed between phases in direct contact with food. Although there are different sources, such as lipids and carbohydrates, proteins are popular due to their abundance and their nutritional qualities. Protein for film elaboration can be extracted from cereals (gluten, prolamins), milk (casein, whey), muscle (myofibrillar), and the connective tissue (gelatin) of marine or terrain species. Requirements may vary depending on their future application; therefore, it cannot be said that 1 source or the other is better, because film properties will also differ due to their method of obtention. Therefore, it is necessary to know what kind of film is needed in order to choose the most suitable one.

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.

In the present work the myosin molecule from jumbo squid mantle (Dosidicus gigas) was isolated and characterized with the aim to evaluate the influence of ionic strength on its gelling properties. It was found that the myosin molecule possesses different chemical and structural characteristics than other vertebrates and invertebrates species, such as some cephalopods, which might explain differences in gelation in comparison to those from other organisms. A lower content of total sulfhydryl groups (TSH) possibly caused an improvement in the myosin molecule flexibility when the ionic strength increased (p ˂ 0.05). The aforementioned possibly affected (p ˂ 0.05) the enzyme activity, surface hydrophobicity, viscosity and RSH groups. The results demonstrate that the myosin molecule from jumbo squid is structurally different from the rest of the marine species.En la presente investigación se aisló y se caracterizó parcialmente a la miosina del manto de calamar (Dosidicus gigas), con el objetivo de estudiar el efecto la fuerza iónica sobre la propiedad gelificante. Se encontró que la miosina de esta especie presenta características químicas y estructurales distintas al de otras especies de vertebrados e invertebrados, como algunos cefalópodos, lo cual explica las diferencias encontradas en la gelificación, en comparación con otros organismos. En especial, se encontró un contenido menor de grupos sulfhidrilos totales (SHT), lo cual posiblemente repercutió en una mayor flexibilidad de la molécula de miosina al aumentar la fuerza iónica, repercutiendo significativamente (p ˂ 0,05) en un aumento en la actividad enzimática, hidrofobicidad de superficie, grupos SHR y viscosidad. Los resultados demuestran que la molécula de miosina del calamar gigante (D. gigas) presenta diferencias estructurales con respecto al resto de la especies marinas.

Different studies on obtaining protein concentrates or surimi from giant squid (Dosidicus gigas) have reported that soft gels are obtained in comparison with other fish species. Therefore, the aim of this research was to investigate the effect of the setting (30 and 60 °C, for 0, 30, 60, and 90 min) on the gelling capacity as a possible alternative to improve the textural characteristics of the gels. Treatments at 60 °C (G4, G5, and G6) had a higher percentage of insoluble protein, while the electrophoretic profile showed the presence of high molecular weight (HMW) aggregates, as well as the decrease of myosin, paramyosin and actin bands as the incubation time was increased. Likewise, these systems presented a lower content of total sulfhydryl (TSH), which is attributed to the formation of disulfide bridges. The texture profile analysis (TPA) showed that the setting application affected the different parameters evaluated (strength, elasticity, and cohesiveness). Setting as pretreatment did not prove to be a good alternative for the gelling of proteins from giant squid mantle, since the control treatment (no setting) was that which exhibited better textural characteristics.