Mechanisms of changes in protein hydrolysis and taste improvement during ultrasound-assisted processing of marinated beef

To investigate the mechanism of ultrasound-assisted marination on beef protein hydrolysis as well as taste improvement, protease activity, protein degradation, protein surface morphology, flavor precursors, and E-tongue analysis of ultrasound-assisted marinated beef were determined. Meanwhile, beef marinated with ultrasonic assistance at 500 W (US500) exhibited the best results in terms of taste, saltiness, umami, and richness, with values that were 2.52, 1.02, and 1.16 times higher, respectively, compared to traditionally marinated samples (NUS). The activity of leucyl aminopeptidases in protease was the highest, and US500 group was 10% and 34% higher than US300 and NUS group, respectively. The effects of ultrasound-assisted marination on the degradation of beef proteins and the morphological changes were confirmed by the myofibrillar fragmentation index, the proteolysis index, and by the Sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Significant increases in nine free amino acids were determined; 27 key differential metabolites were identified by LC-MS/MS. Correlations between metabolites and taste parameters were validated, meanwhile changes in amino acids and key differential metabolites dominated by Lys, Arg, Glu, Met, oxoadipic acid, justicidins, guanosine, capric acid, and 3-dehydro-scyllo-inosose may be the main reason for the improved taste of ultrasound-assisted marinated beef. • Ultrasound-assisted marination contributes to beef proteolysis and taste improvement. • Ultrasound-assisted marination enhances protease activity and FAA accumulation. • Leucyl aminopeptidase is a key protease for regulating proteolysis in marinated beef. • Metabolites such as Glu were mainly responsible for improved taste of marinated beef.