Madín Reservoir (MR) is located on the Río Tlalnepantla in Mexico. Previous studies seeking to identify pollutants at this site evidence that MR water contains a considerable metal load as well as nonsteroidal anti-inflammatory drugs (NSAIDs) at concentrations above those determined suitable for aquatic life. This study aimed to evaluate whether chronic exposure to pollutants in MR alters oxidative stress status and flesh quality in muscle of the common carp Cyprinus carpio. The following biomarkers were evaluated in muscle of carp caught in the general area of discharge from the town of Viejo Madín: hydroperoxide content (HPC), lipid peroxidation (LPX), protein carbonyl content (PCC), and activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx). Physicochemical and textural properties of muscle were also evaluated. Results show that the metals Al and Fe were accumulated in muscle of C. carpio at levels of 21.3 and 29.6 μg L(-1), respectively, and the NSAIDs diclofenac, ibuprofen, and naproxen at levels from 0.08 to 0.21 ng L(-1). Fish exposed to discharge from the town of Viejo Madín showed significant increases in HPC (9.77 %), LPX (69.33 %), and PCC (220 %) with respect to control specimens (p < 0.05). Similarly, enzyme activity increased significantly: SOD (80.82 %), CAT (98.03 %), and GPx (49.76 %). In muscle, physicochemical properties evidenced mainly significant reductions compared to control values while textural properties showed significant increases. Thus, water in this reservoir is contaminated with xenobiotics that alter some biological functions in C. carpio, a fish species consumed by the local human population.

The effect of an edible coating (EC) with 1.5% chitosan as an additive, on common carp (Cyprinus carpio) fillet, was determined evaluating the biochemical, physicochemical, textural, microbiological, and nutritional characteristics periodically during its storage in the freezer (−18°C), observing a decrease in the rate of biochemical reactions related to degradation (p < 0.05), hydroperoxides content (HPC) (0.8324 nM hydroperoxides/mg of protein versus 0.5540 nM/mg with regard to the EC sample), as well as protein carbonyl content (PCC) (0.5860 nM versus 0.4743 nM of reactive carbonyl groups/mg of protein of noncoated material), keeping properties for a longer period of time, and a lower protein solubility (7.8 mg of supernatant protein/mg of total protein versus 6.8 mg/mg) and less loss of moisture (8% less, with regard to EC); for the nutritional characteristics of the fillet, lysine is the limiting aminoacid in the sample without EC, while leucine is the limiting aminoacid for the EC sample. According to microbial growth, the count was 2.2 × 105 CFU/g of sample in mesophiles versus 4.7 × 104 in the EC sample. The results indicate that the use of EC added with chitosan maintains the quality of the product regarding lipid and protein oxidation until fourth month of storage, maintaining moisture content without variation for at least 3 months, and inhibits microbial growth up to 2 logarithmic units, during five months of frozen storage.

Edible coatings have recently been developed and applied to different food matrices, due to their numerous benefits, such as increasing the shelf life of foods, improving their appearance, being vehicles of different compounds, such as extracts or oils of various spices that have antioxidant and antimicrobial activity, as well as being friendly to the environment. The objective of this research was to develop a new edible coating based on chitosan enriched with peppermint extract and to evaluate its effectiveness to inhibit microbial development in vitro and improve both the quality and shelf life of common carp (Cyprinus carpio) during refrigerated storage (4 ± 1 °C). Three treatments were used: edible coating (C + EC), edible coating +, 5% chitosan (C + ECCh) and edible coating + 1.5% chitosan + 10% peppermint (C + ECChP). Prior the coating carp fillets; the antibacterial activity and antioxidant capacity were evaluated in the peppermint extract and coating solutions. After coating and during storage, the following were determined on the fillet samples: microbiological properties, observed for ECP, an inhibition halo of 14.3 mm for Staphylococcus aureus, not being the case for Gram-negative species, for ECCh, inhibition halos of 17.6 mm, 17.1 mm and 16.5 mm for S. aureus, Salmonella typhimurium and Escherichia coli, respectively; for the ECChP, inhibition halos for S. aureus, S. typhimurium and E. coli of 20 mm, 17 mm and 16.8 mm, respectively. For the physicochemical characteristics: an increase in solubility was observed for all treatments during storage, reaching 46.7 mg SN protein/mg total protein for the control, and values below 29.1 mg SN protein/mg total protein (p < 0.05), for fillets with EC (C + EC > C + ECCh > C + ECChP, respectively at the end of storage. For the pH, maximum values were obtained for the control of 6.4, while for the fillets with EC a maximum of 5.8. For TVB-N, the fillets with different CE treatments obtained values (p < 0.05) of 33.3; 27.2; 25.3 and 23.3 mg N/100 g (control > C + E C > C + ECCh > C + ECChP respectively). Total phenolic compounds in the aqueous peppermint extract were 505.55 mg GAE/100 g dried leaves, with 98.78% antioxidant capacity in the aqueous extract and 81.88% in the EC. Biomolecule oxidation (hydroperoxide content) had a significant increase (p < 0.05) in all treatments during storage, 1.7 mM CHP/mg protein in the control, to 1.4 in C + EC, 1.27 in C + ECCh and 1.16 in C + ECChP; TBARS assay values increased in the different treatments during refrigerated storage, with final values of 33.44, 31.88, 29.40 and 29.21 mM MDA/mg protein in the control; C + EC; C + ECCh and C + ECChP respectively. In SDS -PAGE a protective effect was observed in the myofibrillar proteins of fillets with ECChP). The results indicate that the C + ECCh and C + ECChP treatments extend the shelf life of 3–5 days with respect to microbiological properties and 4–5 days with respect to physicochemical characteristics. A reduction in lipid and protein oxidation products was also observed during refrigerated storage. With these findings, this is considered a promising method to increase the shelf life of fish fillets combined with refrigeration and we are able to recommend this technology for the fish processing industry.

Jumbo squid (Dosidicus gigas) is a commercially valuable mollusk in Mexico; 80% of its body is edible. Despite the high protein content (∼18%) and low cholesterol content of this species, its high proteolytic activity (microbial and endogenous enzymes) induces protein degradation and consequent reduction in functional properties from a structural viewpoint. Gelation capacity (texture profile of the gels obtained), solubility, water holding capacity, foaming capacity, emulsification capacity, and emulsion stability were evaluated in protein concentrates obtained by foam‐aided pH‐shift processing: (A) myofibrillar protein extraction with distilled water and no pH‐shifting; (B) alkaline solubilization and isoelectric precipitation; (C) acidic solubilization and isoelectric precipitation; and (D) process A and isoelectric precipitation. Process B showed superior gelation capacity, D had high emulsion stability across a wide range of pH values (4.0–8.0) and C lower plate counts of aerobic mesophilic. Therefore, all three alternative extraction processes showed techno‐functional advantages. Practical Application Jumbo squid is an abundant protein source in México, most of which is exported. Functional and physicochemical properties of muscle protein were improved by pH‐shift processing. The recovered protein showed modifications of technological properties, using one of the methods described can lead to produce a protein extract with the most desirable attributes, such as foaming, emulsifying, or gelling capacities. The functional and physicochemical properties of protein from squid can be enhanced by selecting a certain pH‐shift processing, depending on the desirable use. There is a broad perspective on the use of these protein extracts as ingredients or additives.

The aim of this work was the obtention and characterization of protein hydrolysates from squid muscle frozen stored as an alternative of fermentation substrate. Hydrolysates' antioxidant, antimicrobial and functional properties were obtained by fermentation via Bacillus subtilis ATCC 6633, using Dosidicus gigas mantle, stored for 20 months at -20° C. Culture media with different proportions of collagen: muscle (C0 = 100% muscle, C25 = 75% muscle + 25% collagen, C50 = 50% muscle + 25% collagen, C75 = 25% muscle + 75% collagen, C100 = 100% collagen) of giant squid, were subjected to fermentation, from 0 to 8 hrs. Free radical scavenging activity was determined via the ABTS•+ methodology (maximum value of 3.99±0.02 mg L-ascorbic acid equivalents for 8 h-C25) and DPPH• (maximum value of 750.29±13.57 µg L-ascorbic acid equivalents for 8 hC75). Inhibition zones (between 10 mm and 14.9 mm) were found in hydrolysates, with 8 hrs of fermentation for Gram-negative bacteria. Regarding infrared spectroscopy, after 8 hrs of fermentation, several peaks were detected, which suggest the presence of aromatic rings (1582 cm-1, 856 cm-1 and 756 cm-1), in addition to peaks that suggest the presence of surfactant from B. subtilis (1510 cm-1, 1392 cm-1 and 1198 cm-1). A maximum of 150% (v/v) in the foaming capacity of 2 h-C100 and 87.5% (v/v) of 8 h-C50 was obtained; for foam stability, 77.5% (v/v) with 2 h-C100 and 22.5% (v/v) with 0 h-C0. The maximum value for the emulsifying activity index was 1778.06±30.85 m2/g of protein for 8 h-C0, while the highest index of emulsion stability was 82.04±2.81 mins for 8 h-C25. The protease activity present in the hydrolysates decreased the hardness of the gelatin to 29.6%. Results showed that the use of the giant squid stored for extended periods in freezing conditions impedes its spoiling and harmful effects on the environment, and allows the obtention of hydrolysates with antioxidant, antimicrobial and functional properties, for which the submerged fermentation with B. subtilis ATCC 6633 is suitable for the acquisition of bioactive peptides, which can be considered for their use in the food and pharmaceutical industries.