Effect of vapor pressure on the rate of softening of fish bone by super-heated steam cooking

The softening process of fish bone was studied to utilize fish bone as a calcium source in human diet. To reduce the loss of soluble components of fish tissue during cooking, heating by super-heated steam was examined. Since drying of fish tissue might occur during super-heated steam cooking, the softening rate of mackerel spine and the moisture loss of mackerel meat cooked in super-hated steam were determined for samples cooked at 120°C and 130°C under pressures in the range from 1.2kgf•cm-2 to 2.7kgf•cm-2 (absolute pressure). The softening reaction conformed to an apparent first-order reaction. The softening rate constant apparently depended on the pressure of the super heated steam and not on the temperature of the steam. It is interpreted from the results that the temperature of the spine was the saturation temperature of the super-heated steam which depends only on the total pressure and is independent of the temperature of the super-heated steam. The softening rate constant was represented by an Arrhenius type equation, as following: log (k)=12.2-5.96×103 (1/T ?? ), k: the softening rate constant (s-1), T ?? : the saturation temperature of the super-heated steam. The loss of moisture during cooking was small (2.5%-7.9%).