Abstract:

The effects of sodium tripolyphosphate (TPP) and sodium pyrophosphate (SPP) at various concentrations on the
structure of myofibrillar proteins from grass carp muscle were studied. With an increase in the amount of two phosphates,
the solubility of myofibrillar proteins increased obviously, while the turbidity decreased. The total and active sulfydryl
contents as well as the hydrophobicity of myofibrillar proteins increased with increasing concentration of phosphates.
The secondary structure of myofibrillar proteins was studied by circular dichroism, and the content of α-helix decreased
accompanied by a final increase in β-sheet due to the change of the interaction force that maintained the structural stability.
These results indicated that the two phosphates could influence the structure of myofibrillar proteins mainly through the
increase in solubility, ionic strength and interaction force, which induced unfolding of the protein chain and expansion of the
spatial distance of protein so as to alter the properties of myofibrillar proteins. In addition, SPP had more obvious effect on
the protein structure than TPP when added to the myofibrillar proteins.

Key words: myofibrillar proteins, phosphate, sulfydryl, hydrophobicity, secondary structure