Effects of Characteristics Changes of Collagen on Meat Physicochemical Properties of Beef Semitendinosus Muscle during Ultrasonic Processing

Low-frequency and high-power ultrasound (40 kHz, 1,500 W) was tested for its effects on the characteristics of intramuscular heat-insoluble collagen and meat quality and textural properties of beef semitendinosus muscle. Meat steaks (2.5 x 5.0 x 5.0 cm, 100 +/- 5 g) were sonicated for 10, 20, 30, 40, 50, and 60 min, respectively. Characteristics changes of collagen and meat quality and texture were estimated. The results indicated that ultrasound treatment had no significant (P > 0.05) effects on L* (lightness) and a* (redness) values but decreased b* (yellowness) value significantly when sonicated for 30 min (minimum 6.98). Ultrasound treatment significantly (P < 0.01) reduced the muscle fiber diameter and filtering residues but had no significant effects on the content of heat-insoluble collagen. Significant differences (P < 0.05) in beta-galactosidase and beta-glucuronidase activity were found between ultrasound treated for 10 min (reached the minimum were 5.2 x 10(-3) and 1.6 x 10(-3) umola (TM) ml(-1)a (TM) min(-1), respectively) and control samples. Thermal characteristics analysis of collagen suggested that ultrasound treatment weaken the average stability of collagen. After ultrasound treatment, collagenous fibers were disordered and staggered significantly; fiber arrangement became loose; and the denaturing, granulation, and aggregation of collagen fiber appeared in the extracellular space. Those changes on collagen characteristics had significant effects on meat textural properties. The results suggested that low-frequency and high-power sonication had a significant effect on collagen characters and meat textural properties.