precipitated
if the ionic strength was decreased to less than 0.1,
however, Shimizu and Ikeda (1979) claimed that the “rate of precipitation”
was a function of Mf-P level rather than ionic strength.
Accordingly, in the presence of Mf-P in dilute solution (1:22.5
press juice:deionized water) the “rate of precipitation” of Sp-P
increased from 5% to 6%, 58% in the absence and presence of
Mf-P, respectively. They hypothesized that at low ionic strength,
the extraction of Sp-P from the dark-muscle fish species was reduced
mainly by the interaction between myogen and Mf-P, not
the high globulin content of the Sp-P. Quoting from Nakagawa
and Nagayama (1988), the extractability of proteins such as Sp-P
cannot necessarily be directly equated with their solubility. In
addition, some Sp-P although soluble in a specific solvent, may
not be extractable from muscle tissue in that same solvent because
they may be located in a site inaccessible to the solvent
or are bound rather than “free” (Hultin and Kelleher
2000).