Effects of ultrasound on the beef structure and water distribution during curing through protein degradation and modification

The objective of this study was to explore the mechanisms of power ultrasound (PUS, 150 and 300 W) and treatment time (30 and 120 min) on the water-holding capacity (WHC) and tenderness of beef during curing. Beef muscle at 48 h post mortem was subjected to PUS treatment at a frequency of 20 kHz. Analysis of compression loss and shear force showed that PUS-assisted curing significantly increased the WHC and the tenderness of beef compared to static brining (p < 0.05). According to the analysis of LF-NMR, PUS treatment could increase the P21 values which indicated an improvement in water-binding ability of beef muscle. SDS-PAGE and LC-ESI-MS/MS analysis suggested that PUS induced moderate oxidation of myosin causing polymerization, which may contribute to increased water retention. On the other hand, an increased tenderness of beef is suggested by the increased MFI values and proteolysis of desmin and troponin-T. Transmission electron microscopy (TEM) further supported the effects of PUS on WHC and tenderness changes due to the swelling and disruption of myofibrils. Thus, these results provide knowledge about the mechanism for improving WHC and tenderness of beef by PUS curing, which could be employed as an emerging technology for various meat curing processes.