Effect of multi-frequency ultrasound thawing on the structure and rheological properties of myofibrillar proteins from small yellow croaker

•Ultrasound modes had effects on the structure of myofibrillar proteins (MPs).•Dual-frequency 20/40 kHz ultrasound thawing (DUT) was best thawing method.•DUT can effectively minimized the changes in MPs structure during thawing process.•MPs pretreated by DUT had less aggregation and degradation.•DUT protect the rheological behavior during the thawing process. The influence of multi-frequency combined ultrasound thawing on primary, secondary, and tertiary structures, electrophoresis pattern, particle size distribution, zeta potential values, thermal stability, rheological behavior, and microstructure of small yellow croaker myofibrillar proteins (MPs) were studied. Four treatments were used for thawing small yellow croakers: flow water thawing (FWT), mono-frequency ultrasonic thawing (MUT), dual-frequency ultrasonic thawing (DUT), and tri-frequency ultrasonic thawing (TUT). Compared with fresh samples (FS), the MPs of the sample pretreated by DUT had non-significant effect on protein primary (including free amino groups and surface hydrophobicity), secondary, tertiary structures, electrophoresis pattern, and microstructure. MPs pretreated by DUT had less aggregation and degradation. Besides, DUT treatment increased the thermal stability of MPs. The ultrasound had significant effects on the rheological properties of MPs. Overall, DUT effectively minimized the changes in MPs structure and protected the protein thermal stability and rheological behavior during the thawing process.