Abstract:Beef tendon meat was taken as the research object, and the beef was braised by three methods, namely braising under different vacuums, braising under different ultrasonic powers in synergy with vacuum, and braising under different ultrasonic frequencies in synergy with vacuum. The changes in the salt content, moisture content and weight of the braised beef during the braising processes were measured to examine the mass transfer patterns of the ultrasonic-vacuum braised beef. The results show that the changes in the salt content increased with the increases of vacuum degree, ultrasonic power and ultrasonic frequency, whilst the changes in the moisture content and weight decreased with the increases of vacuum degree, ultrasonic power and ultrasonic frequency. The kinetic parameters associated with the salt content changes of braised beef during braising process, k1 and k2, of variation are related to the vacuum degree, ultrasonic power and ultrasonic frequency. Under the conditions of vacuum degree of -0.043 MPa, ultrasonic frequency of 28 kHz and ultrasonic power of 1 000 W, the maximum effective diffusion coefficient De for the salt content change was 1.42×10-4 m2/s. The mass transfer driving force of the three braising methods had a good positive linear relationship with t0.5/l. Vacuum braising and ultrasonic in synergy with vacuum braising had significant effects on the microstructure of the braised beef. Therefore, ultrasonic in synergy with vacuum braising had a significant effect on the mass transfer in the braised beef and could promote the mass transfer process. The optimal mass transfer conditions for the braising under ultrasonic in synergy with vacuum were: vacuum degree, -0.043 MPa; ultrasonic frequency, 28 kHz; ultrasonic power, 1 000 W; ultrasonic time, 30 min.