Abstract
The Present experiments were carried out on freezing of round type of yellowfin tuna / albacore to measure the internal pressure which causes gape and heave of frozen body during the CaCl2 brine immersion freezing under outer pressure and to forstall these undue defects on frozen foodstuffs by the internal pressure. Both of the temperature and the internal pressure of yellowfin tuna / albacore were measured and recorded continuously by a temperature sensor and a pressure sensor during the freezing.
The results were that frozen body supported to resist against considerable pressure during the freezing under outer pressure and that gape of frozen body was created by the internal pressure during the freezing when the body had been coverd with many scales or could not be expanded during the freezing. The empirical result that the thick spherical body under outer and internal pressure like round type tuna stacked in a fish hold always caused gape and heave during freezing was theoretically supported. The internal pressure or stress of frozen bodies was released by a thermal equalizing process during freezing
