Effects of Ultrasound on Microstructure and Enzyme Penetration in Beef Longissimus lumborum Muscle

The present study aims to introduce a novel process for improving enzyme diffusion in meat during artificial tenderization. For this purpose, Longissimus lumborum muscles from five young Holstein bulls were cut into 3 x 3 x 3 cm pieces. The samples thus prepared were then treated with 0.1% papain solution and the ultrasonic probe (20 kHz; at 100 and 300 W for 10, 20, and 30 min) under different experimental conditions. For each treatment, total proteolytic activity and muscle microstructure were studied using light and field emission scanning electron microscopy techniques while sensory properties were also investigated. Results indicated that sonication power and duration had significant effects on enzyme activity. The highest activity was observed when an ultrasound radiation of 100 W was applied for 20 min. Compared to the untreated meat, ultrasonically treated meat, and meat immersed in sonicated papain, the deepest part of the sample exposed simultaneously to both enzyme and ultrasound treatments recorded proteolytic activities higher by 62, 25, and 42%, respectively. Although all the treatments caused microstructural damages in beef, the most severe changes and the highest scores for tenderness and flavor were achieved through simultaneous application of papain and ultrasound, which indicates papain penetration into the internal parts of meat. Based on the results obtained, ultrasound technology may be recommended as a useful means to achieve enhanced enzyme diffusion in meat.