Possible mechanisms of sequential and simultaneous ultrasonic thawing modes affecting the quality of small yellow croaker

The effect of ultrasonic thawing with different ultrasound working modes on the quality of quick-frozen small yellow croaker and its myofibrillar protein (MPs) structures and functional characteristics were investigated. Flow water (FW), tri-frequency sequential ultrasonic (TSEU), and tri-frequency simultaneous ultrasonic (TSIU) were used for thawing quick-frozen fish. The results showed that the quality of fish thawed by TSEU was the best, while the quality of fish thawed by FW was the worst. Compared to the MPs obtained by TSIU thawing, the MPs obtained by TSEU thawing had more α-helix structure, less β-turns content, smaller oxidation degree, and better thermal gelation ability, which was closest to fresh sample (FS) group. Therefore, compared with TSIU, the TSEU thawing can effectively improve the structure and functional characteristics of the MPs. The thawing loss, hardness and chewiness of fish were mainly affected by α-helix content, and TVB-N value was mainly affected by β-turns.