Ultrasonic Monitoring of the Processes of Blast Freezing and Thawing of Meat

Freezing and thawing strongly affect the structural integrity and quality of meat, yet these processes remain difficult to monitor due to spatial temperature gradients and non-uniform phase transitions. This study investigates the ability of ultrasound to provide real-time detection of dynamic freezing and thawing events in pork tissues with different fat compositions. Specimens of water, lean meat, marbled meat, layered lean-fat structures and lard were subjected to controlled freeze-thaw cycles while ul-trasonic signals and internal temperatures were continuously followed using a custom experimental setup. Consistent amplitude drops in the MHz range at entering the freezing phase followed by characteristic signal patterns that differed sharply between lean and fatty tissues were recorded. Lean meat, dominated by water content, exhibit-ed rapid signal loss at the onset of ice crystallization and a clear recovery of amplitude once fully frozen. Fat-rich tissues demonstrated prolonged attenuation and near dis-appearance of high-frequency signals, with incomplete recovery even at deep-frozen states. Hysteresis between temperature readings and actual phase transition moments was found. These findings indicate that ultrasound provides distinct freeze-thaw sig-natures that reflect tissue composition offering a reliable monitoring tool for freezing uniformity and the true onset and completion of freezing and thawing in meat.