Studies on efficient utilization of water soluble protein-II. Concentration of fish water soluble protein and its gelation properties.

Mackerel water-soluble proteins' concentrates (SPC), which had been concentrated by the ultrafiltration system, were treated with three kinds of methods. The gel formation properties were also studied on the insolubilized SPC. Over 95% of protein in the SPC was insolubilized by two pH shifting methods: One was to adjust the primary pH of SPC lower than 3 then to 7, the other was to adjust the primary pH of SPC higher than 12 then to 7. The preferable gel was obtained by the pH shifting from 12 to 6. An elastic gel like Kamaboko was obtained from SPC by simple heating when SPC was highly concentrated (over 100mg/1). The alcohols caused insolubilization of SPC and the rate of the insolubilization increased with increasing of the carbon chain length of added alcohols. Insolubilized SPC with 50% ethanol formed a gel by heating, but its gelation property was poor. Fish water-soluble proteins were presumed not to cause gelation; we found, however, that the fish water-soluble proteins could form a gel if they were concentrated by an appropriate method like ultrafiltration.