Effect of Ultrasonic Power on the Quality and Myofibrillar Protein Structure of Beef Jerky

In order to improve the hard texture, poor chewiness and unstable quality of traditional beef jerky, the effect of of ultrasonic power on the quality and myofibrillar protein structure of beef jerky, prepared by ultrasonic-assisted marination at different ultrasonic powers (0, 150, 300, 450 and 600 W) and 30 kHz frequency for 30 min followed by natural fermentation for six days, was explored. The quality characteristics of marinated beef strips and beef jerky such as moisture content, water activity, pH, color, salt content and shear force were evaluated. Meanwhile, changes in the myofibrillar fragmentation index (MFI), surface hydrophobicity, carbonyl group content, and total sulfhydryl and active sulfhydryl group contents of myofibrillar proteins in fresh beef strips after ultrasonic treatment were investigated and sensory evaluation of beef jerky were carried out. Results showed that the pH, moisture content, water activity, salt content, L^* value and b^* value of beef jerky increased with the increase in ultrasonic power, while the shear force decreased. Ultrasonic treatment increase the a^* value, whereas the opposite effect was observed at excessively high ultrasonic power. With the increase in ultrasonic power, the MFI, surface hydrophobicity, active sulfhydryl group content and carbonyl group content of myofibrillar proteins increased, while the total sulfhydryl group content decreased (P < 0.05). Sensory evaluation showed that beef jerky with ultrasonic treatment at 300 W had the best overall acceptability. In summary, to maintain color stability and avoid excessive oxidation of protein and energy waste, an ultrasonic power of 300 W was determined as the optimal treatment condition, which could significantly improve the overall quality of beef jerky.