Abstract: In order to understand the changes of protein structure during the processing of spiced beef, protein turbidity, intermolecular interactions, microstructure, secondary structure and water distribution of samples collected at different stages of processing (raw meat, tumble marination, cooking, and secondary sterilization at 90, 100, 110 or 120 ℃) were detected by a microplate reader, a scanning electron microscope, a Fourier transform infrared spectrometer, and a nuclear magnetic resonance analyzer. Results showed that the turbidity of myofibrillar protein extracted from spiced beef was higher than that of sarcoplasmic protein. Tumble marination reduced the turbidity of sarcoplasmic and myofibrillar protein (P < 0.05), whereas heat treatment had the opposite effect. Tumble marination increased the protein-protein interactions, while heat treatment reduced the electrostatic interaction between protein molecules. Hydrogen bond, hydrophobic interaction and disulfide bond were the main intermolecular interaction forces. Different treatments destroyed the structures of sarcoplasmic and myofibrillar protein, and the degree of damage increased with increasing number of processing steps and increasing secondary sterilization temperature. Tumble marination, cooking and secondary sterilization had significant effects on the secondary structure of proteins, the free water content and total water content were the highest after sterilization at 100 ℃ among the four temperatures, and the effect of different sterilization temperatures on the bound water content was not significant (P > 0.05).

Key words: spiced beef; processing technology; interaction force; secondary structure; moisture distribution