Fresh sierra fish (Scomberomorus sierra) fillets were packed in low-density polyethylene films with butylated hydroxytoluene (BHT-LDPE) added. Fillets packed in LDPE with no BHT were used as controls (LDPE). The packed fillets were stored at -25 degrees C for 120 days in which the film released 66.5% of the antioxidant. The influence of the antioxidant on lipid and protein quality, lipid oxidation, muscle structure changes, and shear-force resistance was recorded. As compared to LDPE films, fillets packed in BHT-LDPE films showed lower lipid oxidation, thiobarbituric acid values (4.20 +/- 0.52 vs 11.95 +/- 1.06 mg malonaldehyde/kg), peroxide values (7.20 +/- 1.38 vs 15.15 +/- 1.48 meq/kg), and free fatty acids (7.98 +/- 0.43 vs 11.83 +/- 1.26% of oleic acid). Fillets packed in BHT-LDPE films showed less tissue damage and lost less firmness than fillets packed in LDPE. A significant relationship between lipid oxidation and texture was detected (R2 adjusted, 0.70-0.73). BHT-LDPE films may be used not only to prevent lipid oxidation but also to minimize protein damage to prolong the shelf life of sierra fish.

Pigment compounds were extracted from jumbo squid (Dosidicus gigas) skin with an acid‐ethanol solvent (JSE). Freeze‐dried JSE was characterized with respect to solubility in different solvents, absorption UV–VIS, and FT‐IR spectra, and tested for its radical scavenging activity against ABTS and oxygen radical absorbance capacity (ORAC). The potential ability of JSE for inhibiting oxidation of cod liver oil (CLO) was also determined by monitoring dienes, trienes, peroxide value (PV), thiobarbutiric acid (TBA), and polyene index (PI) in samples stored at 15, 25, and 50°C for 12 days. Concentrations of 0, 0.1, 0.5, 1, and 2% JSE were added to CLO. The yield of JSE was 8.8 mg/g freeze‐dried skin. Solubility behavior, UV–Vis, and FT‐IR spectra of JSE suggests that this pigment extract might belong to the ommochrome family. Moreover, a characteristic xanthommatin peak (1740 cm−1) was observed. JSE exhibited scavenging activity on ABTS•+ radical and in the ORAC assay. After storage PV and TBA increased, whereas PI decreased mainly in the control treatment. The addition of JSE delayed lipid oxidation in CLO during the first 8 days of storage at 50°C. JSE was identified as promising source of antioxidants to retard fish lipid oxidation. Practical applications: This study demonstrates that acid‐ethanol pigment extract from jumbo squid skin, which is a by‐product generated by the squid processing industries, is a valuable antioxidant source. Consistent with the preservative effect observed for this pigment extract, squid skin may be successfully employed to obtain new products for food processing and the pharmaceutical industry, with environmental sustainability benefits and provide a more effective use for jumbo squid by‐products. Acid‐ethanol pigment extracts from freeze‐dried jumbo squid skin (JSE) were added to cod liver oil and stored at 50°C. Increasing levels of JSE (0 < 0.1 < 0.5 < 1 < 2%) led to less lipid oxidation. JSE likely belongs to the ommochromes family.

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.

Food technologists are always looking to improve the functional properties of proteins. In this sense, in last years ultrasound has been used to improve some functional properties. For this reason, and considering that jumbo squid is an important fishery in northwest Mexico, the purpose of this research was to determine the effect of pulsed ultrasound on the physicochemical characteristics and emulsifying properties of squid (Dosidicus gigas) mantle proteins. Pulsed ultrasound (20kHz, 20, and 40% amplitude) was applied for 30, 60, and 90s to a protein extract prepared from giant squid mantle causing an increase (p<0.05) in surface hydrophobicity (S) from 108.4±1.4 to 239.1±2.4 after application of pulsed ultrasound at 40% of amplitude for 90s. The electrophoretic profile and the total and reactive sulfhydryl contents were not affected (p⩾0.05) by the ultrasound treatment. The emulsifying ability of the protein solution was improved (p<0.05), whereas the Emulsifier Activity Index (EAI) varied from123.67±5.52m/g for the control and increased up to 217.7±3.8m/g after application of the ultrasound. The Stability Emulsifier Index (EEI) was improved at 40% of amplitude by 60 and 90s. The results suggested that pulsed ultrasound used as pretreatment induced conformational changes in giant squid proteins, which improved the interfacial association between protein-oil phases, thus contributing to the improvement of their emulsifient properties.

Connective tissue (CT) proteins in jumbo squid (Dosidicus gigas) play an important role because they are the responsible for the union between various cells; hence, there is a close relationship between their functions and muscle firmness during ice storage. In this study, the thermal resistance and solubility of the CT extracted from the fins, mantle and arms of jumbo squid during ice storage (20 days) was evaluated. The CT was fractionated based on solubility [NaCl‐soluble (SSCT) and insoluble (ICT)]. The solubility of the CT was affected during ice storage. An increase in the thermal resistance of the SSCT after 10 days with a subsequent decrease was found in the mantle. Furthermore, the ICT was thermally more resistant than the SSCT in all the anatomical regions. Finally, the electrophoretic profile revealed that structural changes occurred, causing changes in its solubility, due to an increase in the thermal resistance. Practical Applications Jumbo squid (Dosidicus gigas) is an important seafood resource in Mexico, which is commercialized primarily iced and fresh‐frozen. Its muscle connective tissue (CT) has different physicochemical characteristics that differ from other seafood products; it is thermally more resistant and might be responsible for the textural changes during ice storage. Moreover, specific studies about the behavior of CT proteins in such organism may result in improved post‐catch management of jumbo squid muscle, focused on the processing of the species in the food industry or anywhere that CT proteins are used as raw material. The main objective of this research is to investigate solubility changes and thermal resistance of CT proteins of iced jumbo squid mantle.