No substitute substances of sodium chloride exist for strictly salty taste. Small amount of sodium chloride has not only an ability to intensify the sweetness in the sucrose solution (10 to 50%) but also increase the taste of amino acids. For example, for the appearance of the taste of crab meat extract, Konosu et al. reported that sodium chloride was indispensable component to enhance the taste of amino acids. The optimum ratio of sodium chloride to MSG to express the palatability of umami was summarized by Yamaguchi using miso soup. When necessary to decrease to intake the salt, the palatability was given by the arrangement of the concentration of MSG kept 0.38% and decrease in the amount of sodium chloride. To the traditional amino acid related seasoning in Japan; shoyu-soy bean source, the electrodialysis and membrane technology was applied to decrease in the content of salt maintaining the taste of amino acid and flavor. For HVP seasoning produced by hydrolysis of defatted soy bean flake, more colorless and better balance in taste and flavor were requested. To meet this demand, NF membrane which developed as a product of the intermediate between RO membrane and OF membrane was applied to investigate the optimum condition to obtain the good balance of NaCl/TN with changing the membrane of the rejection ability of salt. The solution permeated through NF membrane (Produced by Nitto Denko Co.) was found to be favorable for using as seasoning to pickls, shellfish boiled down and daily processed food to change the tastes milder, when compared with that obtained by the conventional resin process. By passing through the NF membrane, besides the high decolorization, the ratio of the amino acids to sodium chloride comes to be favorable for improvement the taste of seasoning.
The dynamic transport number of counter-ions in Nafion-117 was measured by the limiting current method with a microhole filter. The microhole filter was attached onto the anode side of the Nafion surface in order to fix the thickness of the fluid film. The limiting currents were affected by various conditions of the measurement. A scanning rate of below 10mV/s was required to maintain a steady-state concentration in the laminar film. A scanning rate of above 3mV/s was required to prevent concentration differences between opposite sides of the membrane. Since the porosity of microhole Nuclepore filters decreases with a decrease in pore diameter, the electrical resistance of the microhole filter significantly affected the voltage difference in cases where the pore diameter was below 0.05μm (the porosity below 0.01). Mean while, in case where the pore diameter was above 0.2μm, ionic transport through the microhole filter was not rate-determining. The limiting current was increased by stirring the external solution, because the flux was disturbed and the membrane vibrated. In conclusion, a pore diameter (microhole filter) of 0.08μm, a scanning rate of 5mV/ s and no stirring are the most optimum conditions. The transport number of counter-ions (H+ or Na+) through Nafion-117 decreased by the intrusion of co-ions with increasing external concentration. Non-homogeneity β was obtained as from 0.1 to 0.2 by analyzing the two phase model of ionic transport of H+and Na+, respectively. The measurement of the anion sorbed concentration yielded high non-homogeneity (β= 0.4). It is believed that the large volume of ion-clusters of Nafion was related to the anion-sorbed concentration and the small channels between ion-clusters controlled the transport of the counter-ion.