Josafat Marina Ezquerra-Brauer

Jumbo squid (Dosidicus gigas) mantle collagen: Extraction, characterization, and potential application in the preparation of chitosan–collagen biofilms

Collagen-based biomaterials have been widely used due to its binding capabilities. However the properties and potential use of new collagen sources are still under investigation. Fish by-products are an excellent source of collagen. Thus, acid-soluble collagen (ASC) was extracted, and biochemical and physicochemically characterized from one under-utilized specie, jumbo squid (Dosidicus gigas). In addition, commercial chitosan (95-50%)-ASC (5-50%) blend films were successfully prepared by casting, and characterized by infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC). The molecular masses of the ASC subunits were about 190kDa, 110kDa, and 97kDa, the content of proline and hydroxyproline was 10.9% and 2.8%, respectively. The FT-IR and nuclear magnetic resonance spectra ((1)H NMR) confirmed collagen peptidic crosslinks, and one endothermic peak was found at 119 degrees C. The FT-IR spectrum showed that chitosan and ASC remain linked into the films mainly due to hydrogen bonding. The 85:15 (chitosan:ASC) ratio was selected for its thermal and mechanical analyses. The thermograms of this film indicated the presence of two peaks, one at 87-98 degrees C and the other at 142-182 degrees C. The chitosan:ASC blend produced a transparent and brittle film, with high percentage of elongation at break, and low tensile strength in comparison to chitosan films. D. gigas mantle might be useful as a new source of plasticizer agent in the preparation of biofilms in composites with chitosan.

Controlled release matrices and micro/nanoparticles of chitosan with antimicrobial potential: development of new strategies for microbial control in agriculture

The control of micro-organisms responsible for pre- and postharvest diseases of agricultural products, mainly viruses and fungi, is a problem that remains unresolved, together with the environmental impact of the excessive use of chemicals to tackle this problem. Current efforts are focused on the search for efficient alternatives for microbial control that will not result in damage to the environment or an imbalance in the existing biota. One alternative is the use of natural antimicrobial compounds such as chitosan, a linear cationic biopolymer, which is biodegradable, biocompatible and non-toxic, has filmogenic properties and is capable of forming matrices for the transport of active substances. The study of chitosan has attracted great interest owing to its ability to form complexes or matrices for the controlled release of active compounds such as micro- and nanoparticles, which, together with the biological properties of chitosan, has allowed a major breakthrough in the pharmaceutical and biomedical industries. Another important field of study is the development of chitosan-based matrices for the controlled release of active compounds in areas such as agriculture and food for the control of viruses, bacteria and fungi, which is one of the least exploited areas and holds much promise for future research.

Extruded films of blended chitosan, low density polyethylene and ethylene acrylic acid

The obtaining of chitosan extruded films was possible by using low density polyethylene (LDPE) as a matrix polymer and ethylene-acrylic acid copolymer as an adhesive, in order to ensure adhesion in the interphase of the immiscible polymers. The obtained blend films were resistant; however, a reduction in the mechanical resistance was observed as chitosan concentration increased. The thermal stability of the films showed a certain grade of interaction between polymers as seen in FTIR spectra. The antifungal activity of the extruded films was assessed against Aspergillus niger and high inhibition percentages were observed, which may be mainly attributed to barrier properties of the extruded films and the limited oxygen availability, resulting in the inability of the fungi to grow. A low adherence of fungal spores to the material surface was observed, mainly in areas with chitosan clumps, which can serve as starting points for material degradation.

Efecto de la adición del rotífero Brachionus rotundiformis (Tschugunoff, 1921) sobre la calidad del agua y la producción, en cultivos super-intensivos de camarón blanco del Pacífico Litopenaeus vannamei (Boone, 1931)

Se evaluo la efectividad del rotifero Brachionus rotundiformis como alimento natural exogeno combinado con alimento balanceado sobre los parametros de produccion de Litopenaeus vannamei y la calidad del agua. Se probaron diferentes concentraciones de rotiferos: 0, 5, 10, 15 y 20 rotiferos mL-1 durante 45 dias. No se encontraron diferencias en los niveles de fosfatos entre los tratamientos. El pH fue estadisticamente menor en los tratamientos con 15 y 20 rotiferos mL-1. Los nitratos, nitritos y amonio fueron significativamente menores en los tratamientos con baja concentracion de rotiferos (0 y 5 mL-1), mientras que los valores mas elevados se presentaron en las concentraciones mas altas (15 y 20 mL-1) sin que estas llegaran a ser toxicas. El peso ganado, biomasa, supervivencia y tasa de crecimiento especifico de L. vannamei fueron significativamente mayores en los tratamientos con mayor numero de rotiferos (15 y 20 mL-1), mientras que los valores mas bajos se encontraron en el tratamiento control (0 mL-1). El factor de conversion alimenticia (FCA) fue estadisticamente menor en el tratamiento con mayor concentracion de rotiferos, mientras que el factor de conversion alimenticia (FCA) mas alto se encontro en el tratamiento control. Se concluye que el uso del rotifero B. rotundiformis en altas concentraciones mejora los parametros de produccion del camaron blanco del Pacifico sin llegar a deteriorar de manera importante la calidad del agua

Role of fumonisin B1 on the immune system, histopathology, and muscle proteins of white shrimp (Litopenaeus vannamei)

White shrimps, Litopenaeus vannamei, were tested in two indoor trials to determine the effect of fumonisin B1 on (i) immune response, (ii) histopathology, and, (iii) muscle proteins. Trial 1: (0, 0.5, 0.75 and 1.0μg/g of FB1 levels, 18-day duration; shrimp 5-6g) to evaluate the FB1 effect on the immune system and histopathology response. Trial 2: (0.0, 0.5, 0.75 and 1.0μg/g of FB1 levels, 16-day duration; shrimp 5-6g) to detect FB1 effect on muscle proteins. Prophenoloxidase activity was affected by all FB1 concentrations tested. Both, total haemocyte count and phenoloxidase activity decreased by the 18th day in shrimp exposed to FB1. Marked histological changes in the hepatopancreas of shrimp fed on diet containing FB1, at the all FB1 levels tested, as well as a necrotic tissue were observed. Changes in both, electrophoretic patterns and thermodynamic properties of myosin extracted from shrimp exposed to FB1 were also observed.

Effect of ionic strength on soluble protein removal from giant squid mantle (Dosidicus gigas) and functional evaluation of protein recovery

Myofibrillar protein are the principally responsible of gelling properties in fishery resource, hence, during protein concentrate or isolated proteins preparation, sarcoplasmic protein are discarded; however, myofibrillar protein can support low levels of sarcoplasmic proteins without affecting the gelling property. Therefore, the aim of this study was to gradually remove sarcoplasmic proteins from giant squid mantle by means of different ionic strengths (I). Solutions of NaCl with different ionic strengths (I=0.0, 0.1, and 0.3) were used to obtain 3 protein concentrates. The electrophoretic profile in SDS-PAGE showed differences in protein removal with a high solubility of mantle proteins. The texture profile analysis showed that hardness increased in mantle protein washed with higher I. The total reactive sulfhydryls showed significant changes (p<0.05) detecting major formation of S-S bonds with protein removal at an I of 0.3. Differential scanning calorimetry showed a minor denaturation temperature of the actomyosin complex when protein removal was performed with an I of 0.3. The present study indicates that removal of sarcoplasmic protein as a function of I results in better quality gels.

Chemical and Functional Characterization of Sarcoplasmic Proteins from Giant Squid (Dosidicus gigas) Mantle

Modification of pH and NaCl concentration changed the physicochemical properties of sarcoplasmic proteins (SP) from jumbo squid mantle and consequently their functional properties. Better results of emulsifying activity index (EAI) and foam capacity (FC) were exhibited at pH 11 in NaCl absence due to higher solubility. But better emulsifying stability index (ESI) was obtained at pH 11 in 0.5 M NaCl, while, foaming stability (FS) was better at pH near to isoelectric point (pI). These results suggest that SP from jumbo squid may be a promising ingredient, whose functional properties can be manipulated by changing pH and NaCl concentration.

Effects of pH and Sodium Chloride on the Gelling Properties of a Protein Concentrate Obtained from Jumbo Squid Mantle (Dosidicus Gigas)

Jumbo squid (Dosidicus gigas) is an underutilized fishery resource in the Gulf of California. Jumbo squid muscle could potentially be utilized to manufacture protein concentrates to be used as a base for surimi or as a food ingredient. However, the main problem is the low gelling ability of these protein concentrates compared those of with fish species. Consequently, the present study evaluated the effects of pH and the NaCl concentration on the gelling properties of protein concentrates from squid mantle. According to texture profile analysis, improved gelling properties were obtained at pH 6.0 and 1% of NaCl. During the sol-gel transition, decreased surface hydrophobicity that corresponded to an increased intensity of α-helix structures was detected. Moreover, the total sulfhydryl content decreased during gel formation. Viscoelasticity and water holding capacity analyses showed the formation of a more structured gel at pH 7.0. The higher enthalpy and denaturation temperature detected by differential scanning calorimetry at pH 7.0 and 1% NaCl showed that both variables (pH and NaCl concentration) affected the protein structure and conformation. The results demonstrated that varying pHs and NaCl concentrations improved the gelling properties of protein concentrates from squid.

In vitro antioxidant, antimutagenic and antiproliferative activities of collagen hydrolysates of jumbo squid (Dosidicus gigas) byproducts

Hydrolysates from two different jumbo squid byproducts (fins and arms), produced by trypsin and protease type XIV were compared on the basis of their antioxidant (DPPH and ABTS radical scavenging assays), antimutagenic (Ames test) and antiproliferative (Transformation cell proliferation in M12.C3F6 murine cells) activities. Jumbo squid arms had higher content of collagen than fins, and their hydrolysates had the highest antioxidant activity. Also, jumbo squid arm-derived collagen hydrolyzed with protease XIV showed the highest antimutagenic activity. The four hydrolysates obtained showed low antiproliferative activity, however they are susceptible for further studies to be applied as food additives.

Quality changes during frozen storage of blue shrimp (Litopenaeus stylirostris) with antioxidant, α-tocopherol, under different conditions

Fresh blue shrimp (Litopenaeus stylirostris) muscle was stored with antioxidants under different conditions: ANTIOX 2%, packed in bilayer film of polyamide-low density polyethylene film (PA-LDPE) with 2% α-tocopherol; ANTIOX 4%, packed in PA-LDPE film with 4% α-tocopherol; and ANTIOX-GLAZED, samples stored glazed with 2% α-tocopherol. Shrimps packed in PA-LDPE without α-tocopherol were used as CONTROL. All samples were stored at –20 °C for 120 days. As compared to the CONTROL, the shrimp stored with the antioxidant showed lower lipid oxidation (0.10-0.14 vs 1.58 mgMA/kg of muscle), lost less firmness and astaxanthin content. ANTIOX 2% and ANTIOX-GLAZED showed the lowest concentrations of formaldehyde (0.081-0.083 μM/g). There were no significant differences in color and sensory properties, but differences in the integrity of the muscle fibers were observed. The treatments with α-tocopherol maintained the shrimp muscle quality during frozen storage. However, no significant differences were found between these treatments.