Abstract(1) Orthophosphate, pyrophosphate, Calgon and Phosphate Glass all increase the uncooked volume of minced rabbit muscle by 10‐20, when added at an over‐all concentration of 0.5 to a mixture of equal parts of meat and water. On cooking, the volume falls to between 65 and 75 of the volume of fresh meat. These effects are about the same as that of sodium chloride at an over‐all concentration of 1.(2) When sodium chloride is added to a final concentration of 1, the uncooked volume of the mince is increased by about 30 in the presence of 0.5 of orthophosphate, Calgon, Phosphate Glass or metaphosphate, but by at least 55 in the presence of 0.5 of disodium dihydrogen pyrophosphate (anhydrous). The’cooked volume‘in 1 sodium chloride solution only is about 75 of the original volume of fresh meat. This is increased to about 80 in the presence of the phosphate compounds, except pyrophosphate, when it is increased to at least 95.(3) Detailed study of the effect of 0.25 and 0.5 of pyrophosphate in 1 sodium chloride solution (over‐all concentrations) gives the following average results for the increase in uncooked volume: 1 sodium chloride solution 20 ± 6.0; 1 sodium chloride solution/0.25 pyrophosphate, 51 ± 14; 1 sodium chloride solution/0.5 pyrophosphate, 64 ± 14. The cooked volumes, as a percentage of the volume of fresh meat, were : 1 sodium chloride solution, 71 ± 4.0; 1 sodium chloride solution/0.25 pyrophosphate, 89 ± 8.0; 1 sodium chloride solution/0.5 pyrophosphate, 99 ± 6.0.(4) Pyrophosphate exerts an effect in 1 sodium chloride solution at least twice as great as that of sodium chloride of corresponding ionic strength. The effect is therefore specific, and it is suggested that it consists in the splitting of the contractile protein, actomyosin, into its components and the partial conversion of these from the gel into the sol form.(5) Addition of Ca or Mg ions at the concentrations found in tap‐water does not significantly affect the acti
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