Wilfrido Torres-Arreola

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.

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.

Thermal gelation of myofibrillar proteins from aquatic organisms

ABSTRACT Gelling ability is attributed to myosin, which is the main myofibrillar protein. Therefore, its integrity is very important. However, a gel with good textural characteristics and stability depends on the inherent characteristics of its proteins, as well as on external factors (primarily temperature, pH, protein concentration and added salt). The best gels from aquatic organism proteins are obtained at a pH value of approximately 7.0. However, the concentration of salt is often variable. In contrast, when proteins are recovered using acid/alkaline dissolution, gels with good textural characteristics are obtained without salt. Hydrophobic interactions, disulfide bonds, hydrogen bonds, and electrostatic interactions are the main interactions that stabilize the protein gel. Thus, this review focuses on the study of the main factors involved in protein gelation, as well as on the extraction method effect on the gelling capacity of proteins from aquatic organisms.

Methods to obtain protein concentrates from jumbo squid (Dosidicus gigas) and evaluation of their functionality

Jumbo squid is an important fishery resource in Mexico, and its muscle is lean and white and it has a very low price in the market. It is abundant, but with little or nothing added value, therefore is necessary to search alternatives of processing. Due to muscle characteristics, the aim of this study was to obtain protein concentrates using different methods. They were obtained by means of acidic (acid protein concentrates) and alkaline (alkaline protein concentrates) dissolution. Moreover, a protein concentrate was obtained by direct isoelectric precipitation and by the traditional method (neutral protein concentrates). The yield with better results was alkaline protein concentrates (63.58 ± 1.8%). The gel hardness was significantly different (p < 0.05), especially for the alkaline protein concentrates. The acid protein concentrates, isoelectric precipitation and alkaline protein concentrates were better with regard to the neutral protein concentrates, concerning the emulsifying and foaming properties. The protein concentrates by means of alkaline dissolution gave a better gelling property, but all the processes had the potential to obtain protein with emulsifying and foaming properties.

Aislamiento y caracterización parcial de miosina del manto de calamar gigante (Dosidicus gigas)

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.

Caracterización de hidrolizados de desechos de calamar gigante (Dosidicus gigas) obtenidos por autohidrólisis y un proceso químico-enzimático

Se compararon los hidrolizados obtenidos de los subproductos del calamar gigante (cabeza, tentáculos, piel y mezcla) aplicando dos procesos, autohidrólisis (55°C, pH 5,0 y proteasas endógenas) y químico-enzimático (45°C, pH 2,5 y pepsina), mediante el análisis de proteína soluble (PS), grado de hidrólisis (GH) por el método de ortoftaldehído y por el coeficiente de degradación de proteína (CDP) obtenido por la integración de la información del análisis de la imagen de los geles de SDS-PAGE. En la mezcla de subproductos se analizó el perfil de aminoácidos e hidrofobicidad (SoANS) del hidrolizado. Los valores más altos de PS, GH y CDP lo presentaron los hidrolizados de la cabeza, en ambos procesos. La piel requirió más tiempo para hidrolizarse. Los hidrolizados por autohidrólisis presentaron mayor contenido de aminoácidos y SoANS. La actividad enzimática endógena en subproductos ofrece una alternativa económica para aprovechar la cabeza, tentáculos y piel del calamar gigante.

Interrelation of Collagen Chemical Structure and Nanostructure with Firmness of three Body Regions of Jumbo Squid (Dosidicus gigas)

The chemical structure, thermal denaturation and nanostructure of collagen, obtained from a cation-exchange separation of the mantle, fins and tentacles of jumbo squid (Dosidicus gigas), were comparatively studied. The main idea of this work, was to provide an in-depth understanding of the interdependence between pyridinoline (Pyr) content, helix chemical structure and nanostructure of squid collagen with squid tissue firmness. The tentacles required more shear force and its collagen presented the higher temperature and enthalpy of transition, than the mantle and fins. The tentacle firmness may be explained by the relatively higher imino amino acid content, proline and lysine hydroxylation degrees and Pyr content of its collagen. Moreover, among the regions studied, the collagen from the tentacles had a more intense β band chain. Also, the Fourier transform infrared analysis and Raman spectra, implied that the collagen in the tentacles, was more intermolecularly ordered than the mantle and fins. Consistent with these results, a comparative evaluation of the surface morphology of the three regions, with atomic force microscopy, suggested a more ordered collagen structure in the tentacles (lower roughness values). Based on the above, collagen from tentacles has a higher degree of molecular order that sustains a higher muscle firmness compared to that of other anatomical regions.

Collagen from jumbo squid fin: extracting conditions and influence of the protease system on collagen hydrolysate antioxidant activity

The optimal alkaline and acid conditions for insoluble collagen extraction from jumbo squid fin (JSF) were established by factorial analysis. Dependent variable: protein concentration; independent variables: NaOH and HCl concentrations. The antioxidant properties of JSF collagen hydrolysates obtained by two protease systems were studied. Moreover, jumbo squid skin (JSS) collagen was obtained and hydrolysated under optimal conditions. The optimal extraction condition was 0.5 M NaOH followed by 0.2 M HCl. Collagen α-chains were detected in both JSF and JSS. Collagen β-component was detected only in JSS. JSS collagen showed higher levels of polar and hydrophobic amino acids. The JSF hydrolysates produced by subtilisin showed a lower degree of hydrolysis and higher antioxidant activity (2,2-diphenyl-1-picrylhydrazyl (DPPH), Trolox equivalent antioxidant capacity (TEAC), and oxygen radical absorbance capacity-fluorescein (ORACFL)) than those produced by a mixture of trypsin, chymotrypsin, and peptidase. The JSS hydrolysates showed a higher antioxidant capacity. We have thus established a suitable process to improve the utility of JSF.