Tooru Ooizumi

Effect of tetracosahexaenoic acid on the content and release of histamine, and eicosanoid production in MC/9 mouse mast cell

Abstract6,9,12,15,18,21-Tetracosahexaenoic acid (24∶6n−3) was isolated from a brittle star, Ophiura sarsi Lütken, at>95% purity to evaluate its physiological functions. The effects of 24∶6n−3 on the production of leukotriene (LT)-related compounds such as LTB4, LTC4 and 5-hydroxyeicosatetraenoic acid, and the accumulation and release of histamine in an MC/9 mouse mast cell line were studied. We found that 24∶6n−3 could inhibit the antigen-stimulated production of LT-related compounds as well as other n−3 polyunsaturated fatty acids (PUFA) such as eicosapentaenoic acid (20∶5n−3) and docosahexaenoic acid (22∶6n−3), which are major n−3 PUFA in fish oils; 24∶6n−3 was also shown to reduce the histamine content in MC/9 cells at 25 μM (27% reduction from the control), and the effect was diminished with increase of the fatty acid concentration (up to 100 μM). These two n−3 PUFA, 20∶5n−3 and 22∶6n−3, also reduced the histamine content (16 and 20% reduction at 25 μM, respectively), whereas arachidonic acid (20∶4n−6) increased it (18% increase at 25 μM). Spontaneous- and antigen-induced release of histamine was not influenced with these PUFA (at 25 μM). Ionophore-stimulated release of histamine was suppressed by the PUFA (13,9,15, and 11% reduction with 20∶4n−6, 20∶5n−3, 22∶6n−3, and 24∶6n−3, respectively). The patterns of the effects of 24∶6n−3 on the synthesis of eicosanoids and histamine content were more similar to those of 22∶6n−3 than 20∶5n−3. From these results, 24∶6n−3 can be expected to have anti-inflammatory activity and antiallergic activities similar to those of 22∶6n−3.

Changes of proximate composition and extractive components in narezushi, a fermented mackerel product, during processing

During the processing of mackerel narezushi, the fish body was strongly dehydrated by permeation of salt, the low pH of fish meat, and pressure applied to the fish and rice mixture. In the proximate components, moisture, protein and lipid flowed out from the fish meat into the rice mixture, and sugar permeated from the rice mixture into the fish meat. That the total amount of outflow was larger than that of permeation into the fish is thought to contribute to the decrease in fish body weight during processing. In the extractive components, although the nucleotides completely decomposed, free amino acids and peptides increased remarkably because of the decomposition of proteins in fish meat during processing. Especially, six kinds of free amino acid, Glu, Asp, Gly, Ala, Leu, and Ile, which are thought to be the taste components in marine resources, increased. Organic acid increased remarkably because of the fermentation of rice and permeation into the fish meat. The marked increase of the extractive components is thought to contribute to the umami taste and the sour taste of narezushi.

Changes in physical properties of heat-induced gel on addition of gluconate associated with suppression of myosin denaturation in walleye pollack salt-ground surimi during preheating

Changes in physical properties of two-step heated gels on addition of gluconate were investigated in terms of relationships between breaking strength and gel stiffness. Regression lines between the breaking strength and the gel stiffness were extended to the x-axis (gel stiffness), and the intercept was defined as SBSO. The SBSO of the two-step heated gels increased with gluconate contents in salt-ground surimis, suggesting that the harder but less elastic gels formed on addition of gluconate were dose-dependent. Conversely, the denaturation rate constants of myosin in salt-ground surimis during preheating estimated by means of Ca-ATPase inactivation, loss of salt solubility, and decrease of denaturant solubility were considerably reduced by gluconate. Thus, the progress of myosin denaturation was strongly suppressed. Increments of SBSO (δSBSO) of the two-step heated gels on addition of gluconate were inversely correlated with the denaturation rate constants of myosin in salt-ground surimis for every index. Thus, the changes in physical parameters of two-step heated gel caused by gluconate may be associated with the sluggish progress of myosin denaturation in salt-ground surimi during preheating.

Control of sugar content in fish fillets by soaking and cold preservation

Abstract To control the sugar content in fish fillets, the permeability of various sugar compounds into fillets by soaking together with their dispersing ability inside the soaked fillets were investigated. Irrespective of the kind of sugars, an increase in the osmotic pressure given by sugars in the soaking solution caused the increase in the content of sugars and the decrease in the moisture of the soaked fillets. Comparing the permeability and the dewatering effect of sugars in connection with their molecular weights, lowering the molecular weights of sugars caused an increase in the permeability and a decrease in the dewatering effect. Furthermore, the content of sugars in the external parts were several times higher than those in the internal parts, even when the fillets were soaked for more than 100 h. In contrast, the moisture remained higher in the internal parts than in the external parts of the soaked fillets. Following preservation of the soaked fillets at 4°C for over 50 h was necessary to disperse sugars and moisture in the fillets. Moreover, lowering the molecular weights of sugars also caused an increase in their dispersing ability.

Elution and internal migration of free amino acids in fish meats by soaking in sodium chloride or sorbitol solution

Elution and internal migration of free amino acids (FAA) in fish meats by soaking were investigated when the meat strips were soaked in various concentrations of sodium chloride (NaCl) or sorbitol solution. Rapid decrease of FAA in an earlier phase of soaking was followed by a mild one, irrespective of the kind and the concentration of soaking solution. The loss of FAA by soaking in NaCl solution was slightly larger than that in sorbitol solution. However, regardless of the kinds of soaking solution, the elution of FAA from fish meats by soaking was only dependent on the soaking time, independently of the concentration, namely osmotic pressure of the soaking solution. Conversely, sluggish migration of FAA from the inside to the surface of the meat strips proceeded by soaking. These results suggested that the elution of FAA from fish meats by soaking was driven by a simple diffusion from the surface of the meats to soaking solution, but it was regulated by sluggish migration rate of FAA in fish meats.

Permeation of carboxylates as ionic compounds into fish meats by soaking and its osmotic dehydrating effect

Permeability of Na-gluconate, Na-malate and Na-acetate into fish-meat strips by soaking, and their osmotic dehydrating effects were investigated in comparison with those of sodium chloride (NaCl) and sorbitol. Carboxylic acids, anion species of carboxylates, were less permeable into soaked meats than chlorine of NaCl, and their permeability was similar to that of sorbitol. However, the permeation of sodium, cation species of the carboxylates and NaCl, was promoted with the concentration of free sodium ion dissociated in soaking solutions. The ratio of sodium to the anion species in soaked meats was varied, depending on the numbers of the sodium atom in the molecules as well as the dissociation degree of the ionic compounds in the soaking solution. Furthermore, the osmotic dehydrating effects of Na-gluconate and Na-malate were analogous with that of sorbitol, and higher than those of NaCl and Na-acetate. These results indicated that the permeation characteristics and the osmotic dehydrating effects of the carboxylates were associated with their ionization in soaking solution as well as their molecular weights.