Rehearsal For Thesis Presentation

Wooden breast meat is a common quality abnormality in the pectoralis major muscle of modern commercial broilers. It is mainly characterized by increased muscle hardness, abnormal muscle fiber arrangement, connective tissue proliferation, and changes in water-holding capacity. These characteristics may affect the appearance, processing properties, texture, and sensory quality of chicken breast meat. Because wooden breast meat is often associated with reduced marinade uptake, increased toughness, and abnormal tissue structure, suitable processing treatments are needed to improve its quality and utilization. Therefore, this study aimed to investigate the effects of different ultrasound treatment times on the quality, tenderness, and microstructure of wooden breast chicken meat.Samples were collected from broiler pectoralis major muscles and classified, according to appearance, texture, and tactile characteristics, into a normal breast meat group (NR) and wooden breast meat groups. All samples were vacuum-packaged with 5% sodium chloride solution at a meat-to-solution ratio of 3:1 (w/w). After standing for 30 min, the samples were treated in an ultrasonic water bath at 40 kHz, 400 W, and 20°C. The wooden breast meat samples were assigned to four treatments: U0 (0 min), U1 (60 min), U2 (80 min), and U3 (100 min). The measured parameters included color, pH, marinade uptake, cooking loss, water-holding capacity, shear force, texture profile analysis, lipid oxidation, myofibrillar fragmentation index, histological observation, and sensory evaluation.The results showed that wooden breast meat differed from normal breast meat in several quality characteristics, and the effects of ultrasound treatment varied with treatment time and measured parameter. In raw meat, no significant differences were observed in L* and b* values among groups, indicating that ultrasound treatment had limited effects on raw meat color. In cooked meat, color values changed with treatment time, and the L* and a* values of the U2 group were closer to those of normal breast meat. For pH, the U0 group showed higher raw meat pH than the NR group, while changes in cooked meat pH may be related to heat-induced protein denaturation and ultrasound-induced structural changes.For processing properties, the U0 group had lower marinade uptake than the NR group, whereas the U2 group showed improved marinade absorption. Cooking loss did not differ significantly among groups, suggesting that ultrasound treatment did not clearly reduce moisture loss during heating. In terms of water-holding capacity, U1 and U2 improved the water-holding capacity of raw meat, and U2 showed better performance in cooked meat. However, when ultrasound treatment was extended to U3, some water-holding capacity indicators decreased, suggesting that excessive ultrasound treatment may be unfavorable for moisture retention.For tenderness and microstructure, the U3 group showed a lower shear force value, indicating that longer ultrasound treatment may reduce the shear resistance of wooden breast meat. The myofibrillar fragmentation index was higher in ultrasound-treated groups than in the untreated group, suggesting that ultrasound promoted disruption of the myofibrillar structure. Histological observation also showed that wooden breast meat had irregular muscle fiber arrangement and enlarged inter-fiber spaces. As ultrasound treatment time increased, muscle fiber spaces became wider and structural connections gradually weakened. Overall, ultrasound treatment affected the quality, tenderness, and microstructure of wooden breast chicken meat. Among the treatments, U2 showed better results in marinade uptake, cooked meat water-holding capacity, and some cooked meat color values, whereas U3 had a stronger effect on reducing shear force and loosening tissue structure. These findings suggest that ultrasound treatment has potential to improve selected quality characteristics of wooden breast chicken meat; however, its effectiveness depends on treatment time and targeted quality attributes. Therefore, ultrasound processing conditions should be carefully optimized for practical application.

Keywords: ultrasound, wooden breast meat, water-holding capacity, tenderness, myofibrillar fragmentation index, tissue structure

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