Abstract: Beef longissimus dorsi muscle was treated at different high temperatures (110, 115 and 121 ℃ for 3, 6, 9, 12 and 15 min, respectively). Structural changes in terms of protein chemical bonds, Fourier transform infrared, ultraviolet-visible and fluorescence spectra, and protein fragment size were analyzed in order to investigate the effect of high temperature treatment on chemical forces of beef proteins and the structure of myofibrillar protein. The results showed that contents of ionic bonds and hydrogen bonds in beef proteins significantly reduced (P < 0.05), whereas hydrophobic interaction and disulfide bond content increased significantly (P < 0.05) with increasing temperature and prolonged heating time. The secondary structure of myofibrillar protein was rearranged, and the stretching vibration of N?H and C?N and the bending vibration of N?H were clearly observed. After high temperature treatment, aromatic amino acid residues were exposed on the surface of the molecule, and the local structure of the myofibrillar protein hydrophobic region and the protein tertiary structure were changed. In addition, myofibrillar protein was degraded and aggregated significantly to form a large amount of small molecular mass protein fragments. Therefore, high temperature treatment can significantly change chemical forces of beef proteins and the structure of myofibrillar protein. This finding provides a basis for revealing the mechanisms of change in beef protein at high temperature.

Key words: high temperature treatment, beef protein, chemical forces, myofibrillar protein structure