The effect of supercooling on ice structure in tuna meat observed by using X-ray computed tomography

• Ice crystal in tuna meat frozen by the supercooled freezing was investigated by X-ray CT.
• Ice crystals formed by supercooled freezing were parallel with the myofibers.
• Ice structure was inhomogeneous regardless of the degree of supercooling.
• Cell structure limited ice growth after nucleation from supercooled water in tuna meat.

Several studies have reported that freezing a homogeneous food such as soy bean curd with deep supercooling (supercooled freezing) results in the formation of many particle ice and homogenous ice structure. However, ice crystal morphology may be affected by the cellular structure of the food. In this study, the ice crystal structure in tuna meat, a cellular food, frozen by the supercooled freezing method was investigated by X-ray computed tomography and compared with ice structures in tuna meat frozen by conventional freezing methods. The results showed that rod-like ice crystals grew parallel with the myofibers, and inhomogeneous ice structures formed in tuna meat frozen by the supercooled freezing method regardless of the degree of supercooling, in contrast to the ice structure in frozen soy bean curds. These ice crystals linked with each other to form rod-like ice structures due to mobility limitations imposed by the cellular structure.