Application of multi-frequency ultrasonic thawing on pork: Thawing rate, quality properties and microstructure

This study investigated the effects of ultrasonication on thawing rate, physicochemical properties, water migration, distribution and microstructure of pork at different frequency combination modes (mono-, dual- or tri-frequency sequential and simultaneous modes). The results showed that ultrasonic-assisted thawing increased the thawing rate and shortened the thawing time by 26.72–64.99 % compared to water immersion thawing, and inhibited the lipid oxidation. Regarding the quality characteristics of frozen pork, the samples thawed by combined tri-frequency sequential ultrasound mode (TSEU) at 20/50/35 kHz exhibited better water retention (lower thawing loss and cooking loss) and physicochemical quality (lowest hardness, highest tenderness, lower TBARS values). Low-field nuclear magnetic resonance results displayed that the mobility and loss of bound and free water in pork tissue reduced effectively after ultrasound treatment at 20/50/35 kHz. The microstructure analysis revealed that the microstructure of pork thawed by 20/50/35 kHz was closest to that of fresh meat, and the distribution of muscle fibers was close and regular. Therefore, TSEU at 20/50/35 kHz was considered to be the most appropriate treatment for pork thawing, which could significantly accelerate the thawing rate and maintaining the meat quality.