Tuna Skin Research Articles

Physicochemical Properties of Yellowfin Tuna (T hunnus albacares ) Skin Gelatin and its Modification by the Addition of Various Coenhancers

A gelatin preparation was produced from yellowfin tuna (Thunnus albacares) skins and its physicochemical properties were evaluated against bovine skin gelatin. The fish gelatin obtained exhibited higher gel strength and similar viscosity when compared with its mammalian counterpart, but showed a significantly lower melting point than the latter. In a follow-up study, four compounds (NaH2PO4, MgCl2, CaCl2 and glycerol) at various concentrations were investigated in order to improve fish gelatin's physical properties. Addition of NaH2PO4 at concentrations of 0.3 and 0.5 mol/L yielded gelatin gels that exhibited the highest gel strength, while the highest viscosities were noticed for gelatin solutions containing 0.3 and 0.5 mol/L CaCl2. The highest melting points were observed in the sample gels containing glycerol, irrespective of glycerol concentration. Results suggested that selected physical properties of fish skin gelatin can be modified by the addition of the above compounds at the appropriate concentration levels. Practical Applications Yellowfin tuna (Thunnus albacares) skins are one of the major by-products formed by the fish processing industries in the north central coastal region of Greece. Typically, fish skins along with other by-products, such as bones, heads, scales and viscera, end up as low commercial value products (e.g., animal feed) or dumped into landfills having harmful environmental effects. Utilization of the above by-products, especially of collagen-rich fish skins for gelatin production, will not only increase their commercial value, but it will also open new market opportunities for the gelatin and fish processing industries.

A Novel Base Material for Cosmetics: A Gelatin Vitrigel Membrane Derived from Tuna Skin

A Novel Base Material for Cosmetics: A Gelatin Vitrigel Membrane Derived from Tuna Skin

マグロの皮膚に学ぶ低摩擦船底防汚塗料

マグロの皮膚に学ぶ低摩擦船底防汚塗料

Hepatoprotective action of dietary bluefin tuna skin proteins on CCl4-intoxicated mice

We have shown that dietary bluefin tuna skin (TUS) protects against carbon tetrachloride (CCl4)-induced hepatic damage in mice. The CCl4-induced necrotic area was decreased in mice fed a TUS-containing diet. Consistent with the decreased necrotic area, dietary TUS markedly lowered the elevated serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities and the thiobarbituric acid-reactive substance (TBARS) formation induced by CCl4 injection. TUS diets also decreased phosphorylation of inhibitory kappa B-α and blocked the translocation of nuclear factor-kappa B to the nucleus. TUS is composed mainly (80.7 %) of type I collagen, and our results revealed that dietary tuna collagen peptides (TUCP) attenuated the increased hepatic necrotic area, serum AST and ALT activities, and liver TBARS levels induced by CCl4, similar to TUS, thus enabling us to attribute the hepatoprotective action of TUS in CCl4-intoxicated mice to tuna collagen. Therefore, TUS and TUCP may be potential food resources that are capable of alleviating hepatitis symptoms.

Properties of edible biofilm manufactured from yellowfin tuna (Thunnus albacares) skin gelatin

We investigated the functional properties of gelatin biofilms obtained from yellowfin tuna skin and developed an edible bioflim from fish byproducts to replace mammalian sources. For the biofilms, tensile strength and elongation were 48.57MPa and 15.2%, respectively. The color difference and yellow index values of the biofilms were higher than those of porcine films. The opacity of the biofilms was higher than that of porcine films. In water, the biofilms were stable at pH 4–7. Water vapor and oxygen permeability of the biofilms were 5.3 cm3/m2·day and 110 g/m2·day, respectively. The glass transition temperature and of the thermal stability of the biofilms was 56.30 °C and ∼260 °C, respectively.

Effects of electrolyzed oxidizing water and ice treatments on reducing histamine-producing bacteria on fish skin and food contact surface

This study investigated efficacy of electrolyzed oxidizing water (EO water) and ice (EO ice) treatments in reducing histamine-producing bacteria ( Enterobacter aerogenes, Enterobacter cloacae, Klebsiella pneumoniae, Morganella morganii and Proteus hauseri) on food contact surfaces (ceramic tile and stainless steel) and fish skin (Atlantic salmon and yellowfin tuna). Soaking ceramic tile and stainless steel in EO water (50 ppm chlorine) for 5 min inactivated inoculated bacteria on the surface (>0.92 to >5.4 log CFU/cm 2 reductions). E. cloacae, K. pneumoniae and P. hauseri did not survive well on fish skin. Soaking salmon skin in EO water (100 ppm chlorine) for 120 min resulted in 1.3 and 2.2 log CFU/cm 2 reductions of E. aerogenes and M. morganii, respectively. A treatment of EO ice (100 ppm chlorine) for 24 h was capable of reducing E. aerogenes and M. morganii on tuna skin by 2.4 and 3.5 log CFU/cm 2, respectively. EO water and EO ice can be used as post-harvest treatments for reducing histamine-producing bacteria on food contact surfaces and fish skin.

Using skin mucus RNA to study gene expression in pacific bluefin tuna

The bluefin tuna species have been overfished throughout the world with stocks declining significantly over the past two decades. Studies employing electronic tags describe tunas in extreme ocean environments with depths up to 500 meters and water temperatures ranging from 5 to 33°C. Physiological adaptations such as high cardiac output and endothermy lead tunas to be a good model for studies in cardiac physiology and stress response. However, due to the high cost of tuna maintenance in captivity, studies on tuna physiology and gene expression are rare. Here, we described the use of pacific bluefin tuna (Thunnus orientalis) skin mucus as a possible source for RNA and its potential to be used in gene expression studies of fishes. The skin mucus samples were taken from tunas in captivity at the Tuna Research and Conservation Center and stored at −20°C in RNAlater tubes (Invitrogen). Total RNA extraction from the mucus samples were performed using RNAeasy Kit (Qiagen), posterior RNA clean-up was performed using Ambion Filter Cartridge. The RNA concentration and quality was spectrophotometrically analyzed by A260/A280 ratio and from agarose gel electrophoresis. Reverse transcription of RNA from mucus samples into cDNA was performed using iScript cDNA kit (Bio-Rad). PCR products from mucus cDNA samples, were successfully amplified using bluefin tuna gene specific primers (Hsp70; β-actin; IL-1β). Our results indicate that bluefin tuna skin mucus is a potential source of RNA for gene expression studies in fishes. Funding: NOAA, MBA.

Thermal characterisation of gelatin extracted from yellowfin tuna skin and commercial mammalian gelatin

Glass transition and other thermal characteristics of gelatin from different sources were studied by differential scanning calorimetry (DSC) and modulated DSC (MDSC). The initial glass transition temperatures of equilibrated gelatin samples at 11.3% relative humidity, determined from reversible heat flow thermogram of MDSC, were 23, 75 and 59°C, respectively, for tuna skin, bovine and porcine gelatin. When gelatin samples were equilibrated at higher relative humidity of 52.9%, glass transition temperature of fish skin and bovine gelatin decreased to −3 and 57°C, respectively. Further increase of equilibration relative humidity to 75.3% showed increased value in the case of tuna skin, whereas bovine and porcine did not show any significant change. DSC and MDSC results indicated that tuna gelatin showed lower glass transition compared to mammalian source gelatin equilibrated at the same constant relative humidity. In general glass transition measured by DSC was found lower than the values measured by MDSC. The results in this study showed that the degree of plasticization varied with the source of gelatin as well as their extraction methods.

Isolation and Characterization of Heparin From Tuna Skins

This study characterized heparin isolated from tuna skins. Glycosaminoglycans were isolated from tuna skin after digestion using anion exchange resin. Heparin was eluted from the resin by sodium chloride gradient and was further fractionated by acetone fractionation. Anticoagulant activity was determined using the activated partial thromboplastin time and Heptest assays. Potency was determined using amidolytic antifactor IIa and antifactor Xa assays. The presence of heparin in the extracted tuna skin glycosaminoglycans was confirmed using (13)C-nuclear magnetic resonance. The activated partial thromboplastin time and Heptest clotting times were doubled at concentrations of about 4 and 1 microg/mL, respectively. The clotting time prolongation and antiprotease activity induced by tuna heparin was readily neutralized by 25 microg/mL protamine sulfate. These results demonstrate that biologically active heparin with properties similar to clinical grade heparin can be derived from tuna skin, a raw material with otherwise relatively little economic value.

Extracting optimization and physical properties of yellowfin tuna ( Thunnus albacares) skin gelatin compared to mammalian gelatins

This work is to optimize gelatin extraction from dorsal skin of yellowfin tuna ( Thunnus albacares) using response surface methodology, and to compare physical properties of yellowfin tuna skin gelatin with those of two mammalian skin gelatins (bovine and porcine). Central composite design was adopted in gelatin processing for extracting optimization. Concentration of NaOH ( X 1), treatment time ( X 2), extraction temperature ( X 3) and extraction time ( X 4) were chosen for independent variables. Dependent variables were gel strength ( Y 1) and gelatin content ( Y 2). Optimal conditions were X 1=1.89(%), X 2=2.87 (days), X 3=58.15 (° C) and X 4=4.72 (h), and predicted values of multiple response optimal conditions were Y 1=429.1 (Bloom) and Y 2=89.7 (%). In order to investigate physical properties of yellowfin tuna skin gelatin, gel strength, gelling and melting points, and dynamic viscoelastic properties were measured. The gel strength of yellowfin tuna skin gelatin (426 Bloom) was higher than bovine and porcine gelatins (216 Bloom and 295 Bloom, respectively), while gelling and melting points were lower. Dynamic viscoelastic properties of yellowfin tuna skin gelatin did not change at 20 °C, but increase at 10 °C as a similar pattern with mammalian gelatins.

Gelatin Prepared from Tuna Skin: A Risk Factor for Fish Allergy or Sensitization?

Background: Although fish gelatin may represent a useful alternative to bovine or porcine gelatins, the clearly recognized high prevalence of fish allergy could increase the risk of anaphylaxis to gelatin. The rationale for investigating tuna gelatin rather than gelatins from more allergenic fishes is the availability of an industrial gelatin under development. The infrequent occurrence of tuna allergy should influence the safety of a derived product. The present study investigated IgE antibodies to tuna-skin-derived gelatin in adults and children with documented fish allergy or sensitization. Methods: Serum samples were taken from 100 consecutive patients with fish allergy or sensitization and tested for IgE antibodies against hydrolyzed or nonhydrolyzed gelatin extracted from tuna skin as compared to extracts from tuna flesh, tuna skin as well as bovine or porcine gelatins. Patients with tuna allergies or sensitization were sensitive to the same tuna species (yellowfin) as that from which the gelatin was obtained. IgE antibodies to these various extracts were analyzed using SDS-PAGE and immunoblotting. Results: Only 3 of the 100 serum samples tested gave evidence of reactivity to gelatin extracted from tuna skin. Cross-reactivity between bovine/porcine and fish gelatins was not observed. Conclusion: The risk of adverse reactions to tuna skin gelatin seems to be significantly lower than the risk of fish allergy. Fish gelatin may represent a valuable alternative to bovine or porcine gelatins.

Concentration and desalination of fish gelatin by ultrafiltration and continuous diafiltration processes

Ultrafiltration (UF) of gelatin liquor from marine source (tuna skins) has been performed on a tubular mineral membrane of cut-off 10,000 Da. An attempt was made to concentrate the fish gelatin as well as to purify it by means of the diafiltration technique (DF). Primary experiments were devoted to optimise the UF performances as a function of the main adjustable parameters. The influence of pH, transmembrane pressure, recirculating velocity, and working temperature on both volumetric permeate fluxes and protein retention rates was successively examined. Under the appropriate operating conditions, it was shown that the used membrane can achieve the initial concentration step of the gelatin solutions up to 12 wt% with a protein yield as high as 0.98. In addition, continuous DF proved useful to reduce the salt content of the solutions at an average desalting speed of 185 g/h.m 2 with a few loss of protein in the permeate side.