Ayumi Furutani

Retraction: Growth characteristics of histamine-producing lactic acid bacteria isolated from marinade broth in shimesaba production

To characterize the histamine-producing bacteria isolated from a marinade broth accumulating approximately 25 mg/100 mL of histamine in shimesaba production, taxonomic and physiological features of the isolates were studied. Nineteen strains capable of producing histamine were isolated from a marinade broth by using AC plate agar with the anaerobic culture method and a member of lactobacilli was identiˆed based on the phenotypic characteristics. Moreover, the closest phylogenetic neighbor of the strains was Lactobacillus otakiensis sharing 100  similarity based on 16S rRNA gene sequence. The strains harbored a pyruvoyl-dependent histidine decarboxylase gene, which is widespread in histamine-producing gram positive bacteria. Growth of the strains was inhibited by low pH (below 3.6), low water activity (below 0.939), high salt concentration (above 10), and supplementation of 2 acetic acid (ˆnal concentration). However, all of the strains were able to grow in MRS broth with pH 5.7 at temperatures below 8°C and produce histamine within 4 weeks of cultivation. To prevent histamine accumulation in shimesaba production, it is necessary to use some bacteriostatic conditions, low pH (around 4.0), low temperature (below 8°C), and an appropriate concentration of vinegar, to preserve marinade broth based on the hurdle technology theory.

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.