The effective utilization of water-soluble protein （WSP） from fish that is discarded with waste water during seafood processing is an important challenge for the establishment of sustainable ocean ecosystems and efficient use of unused resources. This review men tions the rheological properties of WSP and their improvement by the addition of other kinds of food proteins and fatty acid salts. Original dilute WSP was concentrated using a hydrophilic polymer derived from sugar. The rheological properties of water-soluble protein concentrate （WSPC） of fish meat were examined with other kinds of protein, such as ovalbumin （OVA） or β-lactoglobulin （β-LG）, and fatty acid salt. The OVA-WSPC or β-LG-WSPC mixture formed a homogeneous gel in the presence of sodium caprate, which is one kind of fatty acid salts. The secondary structure of the proteins was also investigated using Fourier transform infrared spectroscopy （FT-IR）. The α-helix and intramolecular β-sheet structures in the mixed protein were reduced and the intermolecular β-sheet structure was increased by the addition of sodium caprate. These results suggest that WSPC could contribute to changing properties of the fatty acid salt-induced mixed protein gel as a texture modifier. A further topic is the preparation of an edible film using WSP from blue marlin meat.

Flow characteristics of PRO flat sheet membrane modules are researched in relation to the length of the center seal of the feed solution. The permeation performances of the module are examined in experiments and analyzed by means of numerical simulation. It is pointed out that the water permeation decreases with the short center seal, but the pressure loss in the feed solution decreases. The short-cut flow occurs in the feed solution because of the large resistance of the fine mesh of the spacer. There exists a very small flow part ahead of the feed solution so the effective permeation area is decreased. This is closely related to the leakage of salt from the draw solution to the feed solution. The concentration of feed solution accumulates with the leakage of salt. The concentration rapidly increases at the small flow part, and the high concentration continues up to the outlet of feed water. But the short-cut flow decreases the pressure loss in the feed solution so that the power of the feed pump can be decreased.

Removal of sulfate ions from high-concentration sodium chloride （NaCl） aqueous solutions is required in the utilization process of seawater resources including salt manufacturing and desalination. In this study, the performance of commercially available nanofiltration （NF） membranes NFW-TFC-300-500Da （SYNDER FILTRATION INC.） used to remove sulfate ions from high-concentration NaCl aqueous solutions were evaluated. As a result of evaluating the sulfate ion removal performance using NFW-TFC-300-500D, rejection rate for sulfate ions was 0.85 or more, while the rejection rate for chloride ions was 0.06 or less in the range of operating pressure 0.4～0.8 MPa, temperature 15～35 ℃, and sulfate ion concentration 0.01～0.2 mol/L. By applying NFW-TFC-300-500Da, sulfate ions could be removed from high-concentration NaCl aqueous solutions without loss of NaCl.