Isolation and partial characterization of two types of muscle collagen in some cephalopods

Thermal-Induced Autolysis Enzymes Inactivation, Protein Degradation and Physical Properties of Sea Cucumber, Cucumaria frondosa

The main objective is to effectively denature the autolysis enzymes of C. frondosa on the premise of avoiding the quality deterioration caused by overheating. The effects of the different thermal treatments (blanching at 40–80 °C for 45 min, boiling and steaming at 100 °C for 15–120 min) on the cooking yield, moisture content, protein degradation, texture, and enzyme inactivation were studied, and the inner relationship was investigated by multivariate analysis. The autolysis enzymes of C. frondosa were thermally stable and cannot be denatured completely by blanching. Boiling and steaming could efficiently inactivate the enzymes but overheating for 60–120 min reduced the cooking yield and texture quality. Boiling at 100 °C for 45 min was suitable for pre-treatment, with cooking yield of 70.3% and protein content of 78.5%. Steaming at 100 °C for at least 30 min was preferable for long-term storage and instant food, in which the relative activity was only 3.2% with better palatability.

Muscle lysyl oxidase activity and structural/thermal properties of highly cross-linked collagen in jumbo squid (Dosidicus gigas) mantle, fins and arms

Muscle from mantle, fins and arms of squid (Dosidicus gigas) were compared based on lysyl oxidase activity (LOX), chemical/structural and thermodynamic properties of highly cross-linked collagen. The arms collagen presented the highest temperature (Tp) and enthalpy of transition. The arms collagen thermic properties may be explained by the higher imino amino acid content, proline and lysine hydroxylation degrees. Moreover, among the regions, the collagen from the arms had a more intense β band chain, hydroxymerodesmosine peak in the resonance magnetic nuclear spectra and pyridinoline peak in the Raman spectra. Fins showed the highest LOX activity. The LOX activity was associated with the Tp, proline and lysine hydroxylation degrees. These results implied that the collagen in the arms was more intermolecularly ordered than the mantle and fins, and may provide a theoretical basis for a better understanding of the thermal behaviour of squid tissues during management and processing.

Two-dimensional gel and shotgun proteomics approaches to distinguish fresh and frozen-thawed curled octopus (Eledone cirrhosa)

The substitution and sale of frozen-thawed fish labeled as fresh is a widespread, difficult to unmask commercial fraud and a potential risk for consumer health. Proteomics could help to identify markers for the rapid screening of food samples and the identification of frozen-thawed seafood. Using two-dimensional electrophoresis (2-DE) and high-resolution liquid chromatography tandem mass spectrometry (LC-MS/MS), we identified biomarkers that are able to discriminate between fresh and frozen-thawed tissue samples of curled octopus (Eledone cirrhosa). The 2-DE analysis showed a significant reduction in two protein spots (molecular weight of 45-50 kDa, isoelectric point of 6.5-7) identified as transgelin. At shotgun analysis, nine proteins resulted modulated and transgelin was confirmed as down-regulated, making it a potentially useful marker for differentiating between fresh and frozen-thawed fish product samples.

BIOLOGICAL SIGNIFICANCE

This work, based on two different proteomics approaches, investigated differentially expressed proteins in the tentacles of the curled octopus (E. cirrhosa) after freezing-thawing processes. We were able to characterize the proteome of the tentacles, increasing our knowledge on this species, and a common down-regulated protein was identified by 2-DE and shotgun analysis, a calponin-like protein called transgelin, suggesting a potential use as a marker to distinguish different states of conservation in this species.

Evaluation of alternative sources of collagen fractions from Loligo vulgaris squid mantle

Acid-Solubilized Collagen (ASC) and Pepsin-Solubilized Collagen (PSC) were extracted from the mantle of the common European squid, and were comparatively characterized. ASC and PSC were isolated with an extraction yield of 5.1 and 24.2% (on dry weight basis), respectively. SDS-PAGE showed that the ASC was mostly comprised of α1- and α2-chains; while the PSC presented relevant β- and γ-components. GPC analysis confirmed that both the ASC and the PSC consisted of fractions characterized by different molecular weight. Thermal denaturation behavior of ASC and PSC were followed by calorimetric and rheological analyses; denaturation temperature was estimated to be 22°C for ASC and 21°C for PSC. Amino acid composition and solubility of collagen were also investigated. Finally, the cytotoxicity of the isolated collagen was evaluated in vitro and no cytotoxic activity caused by the collagen extracts was observed. This study demonstrated that squid mantle has potential as an alternative source of collagen-derived materials.

Characterization and wound healing property of collagen-chitosan film from Sepia kobiensis (Hoyle, 1885)

The present findings were aimed to develop an effective form of collagen-chitosan film to investigate the wound healing property in Wistar rats. Primarily, the acid-soluble collagen (ASC) isolated, structurally and physicochemically characterized. FT-IR and 1H NMR spectra were confirmed the collagen peptide crosslinks. The molecular weight of ASC subunits was about 86 kDa and 79 kDa, the proline and hydroxyproline content was 13.15% and 7.55%, respectively. In addition, collagen-chitosan films were successfully prepared in a controlled environment and characterized by FT-IR and DSC. In wound healing, the experimental animal model showed the increased wound size reduction in the CChF treated rats (96.25%) when compared to control rats (33.75%) followed by CF treated rats (65%) and ChF (55%). The histological results well supported these findings. It can be concluded that a better and faster epithelization was observed in the CChF group compared to the other groups.

Collagen characteristics of farmed Atlantic salmon with firm and soft fillet texture

The possible role of collagen in texture variations among Atlantic salmon (Salmo salar L.) grown under commercial conditions at a Norwegian farm was studied. The texture was determined instrumentally as the breaking strength, and collagen and its salt (SSC), acid (ASC), pepsin (PSC) and insoluble (IF) fractions were analysed in order to determine the collagen aggregation degree. The collagen solubility and its overall amino acid (AA) composition showed no correlation to the breaking strength, but a positive correlation was observed between the breaking strength and glycine (r=0.74) and alanine (r=0.87) contents of the PSC fraction. Salmon with high breaking strength had higher T(peak) (temperature of transition) and ΔH (enthalpy of transition), and the collagen seemed to have triple helix structures mainly stabilized by covalent associations as compared to salmon with low breaking strength. The glycosylation degree was also positively correlated to the breaking strength (r=0.88, p ≤ 0.05). It is concluded that firmness of salmon muscle was not related to the total amount of collagen in the muscle, but rather higher collagen stability.

Isolation and characterization of collagen from brown backed toadfish (Lagocephalus gloveri) skin

Collagen was isolated and characterized from the skin of brown backed toadfish (Lagocephalus gloveri), processing wastes. The total collagen yield extracted was 54.3% on the basis of lyophilized dry weight compared to other vertebrates. According to the electrophoretic pattern, the skin collagen of the fish consisted of heterotrimer alpha1alpha2alpha3. Moreover, the denaturation temperature was 28 degrees C, which was about 9 degrees C lower than that of collagen from porcine skin. Therefore, there is a possibility to use brown backed toadfish skin collagen as an alternative source of collagen for industrial purposes and subsequently it may maximize the economical value of the fish.