Abstract: Sour pork was prepared from pork longissimus dorsi muscle and the structural changes of proteins were studied during the fermentation process of sour pork. The results showed that the electrostatic force of proteins decreased with fermentation time, while the hydrophobic interaction and the disulfide bonding increased significantly followed by small fluctuations. The results of ultraviolet absorption spectroscopy showed that the aromatic amino acid residues of myofibrillar proteins were shifted to a more hydrophobic environment, and the polarity of the microenvironment around sarcoprotein tyrosine and tryptophan residues increased. The endogenous fluorescence spectra showed that the fluorescence intensity decreased generally, and red shift occurred when compared with before fermentation, which indicates that tryptophan underwent oxidative degradation, and its residues were mainly exposed to the polar environment. Raman analysis showed that the α-helical content decreased, while the β-sheet content increased gradually, and the secondary structure of proteins was reorganized after 110 days of fermentation. These results showed that long-time fermentation could change the secondary and tertiary structures of proteins in sour pork, which explains the effect of fermentation on sour pork quality at the level of protein structure.

Key words: sour pork, fermentation, protein structure, spectral characteristics