Negative roles of salt in gelation properties of fish protein isolate

Salt effect on gelling properties of fish protein isolate (FPI) prepared by acid- and alkali-aided extraction was investigated. Acid- or alkali-extracted FPI formed significantly better gel texture with 0% NaCl than with 3% NaCl. Texture properties of acid- or alkali-extracted FPI decreased as NaCl content increased, especially at 2% to 3% salt. Contrarily, salt significantly promoted texture qualities of conventional surimi gels. The effect was highlighted when they were subjected to low temperature setting. The myofibrillar proteins in FPI were not solubilized when NaCl was added, perhaps due to protein aggregation caused by acid or alkali extraction. FPI solubility, however, was not closely related to their texture properties. Cold setting did not promote texture properties of FPI gels as much as conventional surimi gels. Acid-extracted gels gave the best color properties.